Detection of RAS p.Q61R by Immunohistochemistry in Practice: A Clinicopathologic Study of 217 Thyroid Nodules with Molecular Correlates.

RAS p.Q61R is the most prevalent hot-spot mutation in RAS and RAS-like mutated thyroid nodules. A few studies evaluated RAS p.Q61R by immunohistochemistry (RASQ61R-IHC). We performed a retrospective study of an institutional cohort of 150 patients with 217 thyroid lesions tested for RASQ61R-IHC, including clinical, cytologic and molecular data. RASQ61R-IHC was performed on 217 nodules (18% positive, 80% negative, and 2% equivocal). RAS p.Q61R was identified in 76% (n = 42), followed by RAS p.Q61K (15%; n = 8), and RAS p.G13R (5%; n = 3). NRAS p.Q61R isoform was the most common (44%; n = 15), followed by NRAS p.Q61K (17%; n = 6), KRAS p.Q61R (12%; n = 4), HRAS p.Q61R (12%; n = 4), HRAS p.Q61K (6%; n = 2), HRAS p.G13R (6%; n = 2), and NRAS p.G13R (3%; n = 1). RASQ61R-IHC was positive in 47% of noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP; 17/36), 22% of follicular thyroid carcinomas (FTC; 5/23), 10% of follicular thyroid adenomas (FTA; 4/40), and 8% of papillary thyroid carcinomas (PTC; 9/112). Of PTC studied (n = 112), invasive encapsulated follicular variant (IEFVPTC; n = 16) was the only subtype with positive RASQ61R-IHC (56%; 9/16). Overall, 31% of RAS-mutated nodules were carcinomas (17/54); and of the carcinomas, 94% (16/17) were low-risk per American Thyroid Associated (ATA) criteria, with only a single case (6%; 1/17) considered ATA high-risk. No RAS-mutated tumors recurred, and none showed local or distant metastasis (with a follow-up of 0-10 months). We found that most RAS-mutated tumors are low-grade neoplasms. RASQ61R-IHC is a quick, cost-effective, and reliable way to detect RAS p.Q61R in follicular-patterned thyroid neoplasia and, when malignant, guide surveillance.

Malignant Epithelioid Mesenchymal Neoplasm with FUS::CREM Gene Fusion Arising in the Tongue: A Case Report Detailing Clinicopathological, Imaging, and Molecular Features.

FUS::CREM fusion is a distinct primary driver in rare neoplasms of the head and neck and other anatomic sites. Herein, we describe the clinicopathological, imaging, and molecular features of a malignant epithelioid mesenchymal neoplasm harboring FUS::CREM fusion, arising in the tongue of a 46-year-old male. Clinically, the patient presented with a left upper neck mass. Imaging revealed a 4.0 cm mass at the left base of tongue. Histologically, the tumor consisted of sheets of loosely cohesive, small round to ovoid cells with moderate cytoplasm, small nuclei with coarse chromatin, frequent nuclear pseudoinclusions, and dense peripheral lymphoplasmacytic and histiocytic infiltrates. Malignant features, including tumor necrosis, perineural invasion, and increased mitotic activity were observed; however, lymphovascular invasion was absent with no evidence metastatic disease in the examined lymph nodes. A comprehensive panel of immunohistochemical stains showed positivity for synaptophysin and ALK, with negative results for all other markers. RNA-based next-generation sequencing using anchored multiplex polymerase chain reaction (PCR) was performed and detected FUS::CREM fusion gene. The patient was treated by excision and postsurgical chemoradiation with no evidence of recurrence after four months. Additional cases supported by comprehensive clinical data collected over an extended period are necessary to precisely characterize epithelioid mesenchymal neoplasms harboring FUS::CREM fusion in the head and neck.

FGFR Alterations in Thyroid Carcinoma: A Novel Class of Primary Drivers with Significant Therapeutic Implications and Secondary Molecular Events Potentially Mediating Resistance in Thyroid Malignancy.

Background: Diagnostic classification of thyroid malignancy is primarily accomplished through examination of histomorphological features and may be substantiated and clarified by molecular data. Individual molecular drivers show relatively robust and specific associations with histological subtypes of thyroid malignancy, including BRAF sequence variants and kinase gene fusions in papillary thyroid carcinoma, predominantly RAS variants in follicular-patterned neoplasia, and additional "late" mutations affecting TERT promoter, TP53, and the PI3K/AKT/PTEN pathway in high-grade malignancies. Given the oncogenic role of FGFR, particularly FGFR1-3, the goal of this study was to explore the role of FGFR in thyroid carcinoma biology. Methods: We completed a multicenter retrospective observational study for thyroid carcinomas with pathogenic alterations in the FGFR gene family. We performed this study by querying the molecular data accumulated for thyroid carcinomas from each center. Results: Overall, 5030 sequenced thyroid malignancies were reviewed, yielding 17 tumors with FGFR alterations, including 11 where FGFR was the primary molecular driver and 6 where FGFR was a secondary pathogenic alteration, with a subset for which there was available clinical follow-up data. Of the 11 carcinomas with an FGFR driver, 9 were gene fusions involving FGFR2:VCL (4 tumors), TG::FGFR1 (3 tumors), FGFR2::CIT, and FGFR2::SHTN1, and the remaining 2 were driven by FGFR1 amplification. In the 6 tumors where a canonical driver of thyroid neoplasia was present (5 cases) or no clear primary driver was detected (1 case), sequencing detected secondary FGFR2 p.W290C, p.Y375C, and p.N549K, as well as FGFR1 p.N546K in the respective tyrosine kinase domains, some at subclonal variant allele frequencies. Conclusions: This study presents the first description of a collection of thyroid carcinomas grouped by primary driver alterations in FGFR, as well as a cohort of thyroid tumors with secondary alterations that potentially lead to tumor progression or resistance to targeted therapy. Given the availability of small molecular inhibitors targeting oncogenic FGFR, this study emphasizes the significant implications for patients from identification of FGFR alterations as they are currently under-recognized in the literature and, most importantly, have potential novel treatment options.

Novel prognostic nomogram for predicting recurrence-free survival in medullary thyroid carcinoma.

AIMS: Recently, there have been attempts to improve prognostication and therefore better guide treatment for patients with medullary thyroid carcinoma (MTC). In 2022, the International MTC Grading System (IMTCGS) was developed and validated using a multi-institutional cohort of 327 patients. The aim of the current study was to build upon the findings of the IMTCGS to develop and validate a prognostic nomogram to predict recurrence-free survival (RFS) in MTC. METHODS AND RESULTS: Data from 300 patients with MTC from five centres across the USA, Europe, and Australia were used to develop a prognostic nomogram that included the following variables: age, sex, AJCC stage, tumour size, mitotic count, necrosis, Ki67 index, lymphovascular invasion, microscopic extrathyroidal extension, and margin status. A process of 10-fold cross-validation was used to optimize the model's performance. To assess discrimination and calibration, the area-under-the-curve (AUC) of a receiver operating characteristic (ROC) curve, concordance-index (C-index), and dissimilarity index (D-index) were calculated. Finally, the model was externally validated using a separate cohort of 87 MTC patients. The model demonstrated very strong performance, with an AUC of 0.94, a C-index of 0.876, and a D-index of 19.06. When applied to the external validation cohort, the model had an AUC of 0.9. CONCLUSIONS: Using well-established clinicopathological prognostic variables, we developed and externally validated a robust multivariate prediction model for RFS in patients with resected MTC. The model demonstrates excellent predictive capability and may help guide decisions on patient management. The nomogram is freely available online at https://nomograms.shinyapps.io/MTC_ML_DFS/.

Association of the Genomic Profile of Medullary Thyroid Carcinoma with Tumor Characteristics and Clinical Outcomes in an International Multicenter Study.

Purpose: The prognostic importance of RET and RAS mutations and their relationship to clinicopathologic parameters and outcomes in medullary thyroid carcinoma (MTC) need to be clarified. Experimental Design: A multicenter retrospective cohort study was performed utilizing data from 290 patients with MTC. The molecular profile was determined and associations were examined with clinicopathologic data and outcomes. Results: RET germ line mutations were detected in 40 patients (16.3%). Somatic RET and RAS mutations occurred in 135 (46.9%) and 57 (19.8%) patients, respectively. RETM918T was the most common somatic RET mutation (n = 75). RET somatic mutations were associated with male sex, larger tumor size, advanced American Joint Committee Cancer (AJCC) stage, vascular invasion, and high International Medullary Thyroid Carcinoma Grading System (IMTCGS) grade. When compared with other RET somatic mutations, RETM918T was associated with younger age, AJCC (eighth edition) IV, vascular invasion, extrathyroidal extension, and positive margins. RET somatic or germ line mutations were significantly associated with reduced distant metastasis-free survival on univariate analysis, but there were no significant independent associations on multivariable analysis, after adjusting for tumor grade and stage. There were no significant differences in outcomes between RET somatic and RET germ line mutations, or between RETM918T and other RET mutations. Other recurrent molecular alterations included TP53 (4.2%), ARID2 (2.9%), SETD2 (2.9%), KMT2A (2.9%), and KMT2C (2.9%). Among them, TP53 mutations were associated with decreased overall survival (OS) and disease-specific survival (DSS), independently of tumor grade and AJCC stage. Conclusions: RET somatic mutations were associated with high-grade, aggressive primary tumor characteristics, and decreased distant metastatic-free survival but this relationship was not significant after accounting for tumor grade and disease stage. RETM918T was associated with aggressive primary tumors but was not independently associated with clinical outcomes. TP53 mutation may represent an adverse molecular event associated with decreased OS and DSS in MTC, but its prognostic value needs to be confirmed in future studies.

Critical Appraisal of Histologic Grading for Mucoepidermoid Carcinoma of Salivary Gland: Is an Objective Prognostic 2-tiered Grading System Possible?

Multiple 3-tiered grading systems exist for mucoepidermoid carcinoma (MEC), leading to controversial results on the frequency and prognostic values of each grade. We aimed to identify prognostic histologic factors and to evaluate grading schemes in this retrospective study of 262 resected primary head and neck MECs. The rate of nodal metastasis was 8.4%. Large tumor size, tumor fibrosis, infiltrative border, lymphovascular invasion, perineural invasion, atypical mitosis, mitotic index (MI) ≥4/2 mm 2 (4/10 HPFs), necrosis, and pT4 stage were associated with increased risk of nodal metastasis. The 5-year recurrence-free survival (RFS) was 95%. Significant prognostic factors for RFS included infiltrative border, tumor-associated lymphoid stroma, architectural patterns (macrocystic, microcystic, and noncystic), anaplasia, atypical mitosis, MI, necrosis, lymphovascular invasion, margin, pT stage, and tumor size. Nuclear anaplasia, high mitotic rate, and ≥25% microcystic component were significant independent prognostic factors on multivariate survival analysis. There was no significant difference between low-grade (LG) and intermediate-grade (IG) MECs in terms of risk of nodal metastasis and outcomes using all 4 known grading systems. Rather, high-grade MEC was consistently associated with an increased risk of nodal metastasis at presentation and decreased RFS and distant metastasis-free survival (DMFS) compared with the LG/IG MECs. We therefore recommend simplifying MEC grading to a 2-tiered grading scheme using MI and/or tumor necrosis. Using a 2-tiered grading, high-grade histology independently predict RFS, and is associated with a 25% risk of nodal metastasis, a 5-year RFS of 76%, and a 5-year DMFS of 76%, whereas LG MEC has a nodal metastasis rate of 7.0%, 5-year RFS of 97% and 5-year DMFS of 99%.

Ki67 proliferation index in medullary thyroid carcinoma: a comparative study of multiple counting methods and validation of image analysis and deep learning platforms.

AIMS: The International Medullary Thyroid Carcinoma Grading System, introduced in 2022, mandates evaluation of the Ki67 proliferation index to assign a histological grade for medullary thyroid carcinoma. However, manual counting remains a tedious and time-consuming task. METHODS AND RESULTS: We aimed to evaluate the performance of three other counting techniques for the Ki67 index, eyeballing by a trained experienced investigator, a machine learning-based deep learning algorithm (DeepLIIF) and an image analysis software with internal thresholding compared to the gold standard manual counting in a large cohort of 260 primarily resected medullary thyroid carcinoma. The Ki67 proliferation index generated by all three methods correlate near-perfectly with the manual Ki67 index, with kappa values ranging from 0.884 to 0.979 and interclass correlation coefficients ranging from 0.969 to 0.983. Discrepant Ki67 results were only observed in cases with borderline manual Ki67 readings, ranging from 3 to 7%. Medullary thyroid carcinomas with a high Ki67 index (≥ 5%) determined using any of the four methods were associated with significantly decreased disease-specific survival and distant metastasis-free survival. CONCLUSIONS: We herein validate a machine learning-based deep-learning platform and an image analysis software with internal thresholding to generate accurate automatic Ki67 proliferation indices in medullary thyroid carcinoma. Manual Ki67 count remains useful when facing a tumour with a borderline Ki67 proliferation index of 3-7%. In daily practice, validation of alternative evaluation methods for the Ki67 index in MTC is required prior to implementation.

Update on Molecular Diagnostics in Thyroid Pathology: A Review.

Thyroid nodules are quite common, and the determination of a nodule of concern is complex, involving serum testing, radiology and, in some cases, pathological evaluation. For those nodules that raise clinical concern of neoplasia, fine needle aspiration biopsy is the gold standard for evaluation; however, in up to 30% of cases, results are indeterminate for malignancy, and further testing is needed. Advances in molecular testing have shown it to be of benefit for both diagnostic and prognostic purposes, and its use has become an integral part of thyroid cancer management in the United States and in several global nations. After The Cancer Genome Atlas (TCGA) consortium published its molecular landscape of papillary thyroid carcinoma (PTC) and reduced the "black matter" in PTC from 25% to 3.5%, further work ensued to clarify the remaining fraction not neatly attributed to the BRAFV600E-like or RAS-like phenotypes of the TCGA. Over the past decade, commercial molecular platforms have been refined as data accrues, and they increasingly cover most genetic variants of thyroid carcinomas. Molecular reporting focuses on the nodule tested, including related clinical information for that nodule (size of nodule, Bethesda category, etc.). This results in a comprehensive report to physicians that may also include patient-directed, clear language that facilitates conversations about nodule management. In cases of advanced or recurrent disease, molecular testing may become essential for devising an individual therapeutic plan. In this review, we focus on the evolution of integrated molecular testing in thyroid nodules, and how our understanding of tumor genetics, combined with histopathology, is driving the next generation of rational patient management, particularly in the context of emerging small, targetable therapeutics.

Diffuse Sclerosing Papillary Thyroid Carcinoma: Clinicopathological Characteristics and Prognostic Implications Compared with Classic and Tall Cell Papillary Thyroid Cancer.

BACKGROUND: The clinical behaviour and oncologic outcome of diffuse sclerosing papillary thyroid carcinoma (DS-PTC) is poorly understood. The objectives of this study were to compare the clinicopathological characteristics and oncological outcomes of DS-PTC to classic PTC (cPTC) and tall cell PTC (TC-PTC). METHODS: After institutional review board approval, 86 DS-PTC, 2,080 cPTC, and 701 TC-PTC patients treated at MSKCC between 1986 and 2021 were identified. Clinicopathological characteristics were compared by using chi-square test. Kaplan-Meier and log rank were used to compare recurrence-free survival (RFS), disease-specific survival (DSS), and overall survival (OS). DS-PTC patients were propensity matched to cPTC and TC-PTC patients for further comparison. RESULTS: DS-PTC patients were younger with more advanced disease than cPTC and TC-PTC (p < 0.05). Lymphovascular invasion (LVI), extranodal extension, and positive margins were more common in DS-PTC (p < 0.02). Propensity matching confirmed more aggressive histopathological features in DS-PTC. The median number of metastatic lymph nodes was significantly greater and DS-PTC metastases were RAI avid. DS-PTC 5-year RFS was 50.4% compared with 92.4% in cPTC and 88.4% in TC-PTC (p < 0.001). Multivariate analysis confirmed DS-PTC as an independent prognostic factor of recurrence. Ten-year DSS for DS-PTC was 100% compared with 97.1% in cPTC and 91.1% in TC-PTC. Differentiated high-grade, thyroid carcinoma DS had more advanced T-stage and worse 5-year RFS than DS-PTC. CONCLUSIONS: DS-PTC presents with more advanced clinicopathological features than cPTC and TC-PTC. Large-volume nodal metastases and LVI are characteristic features. Almost half of patients develop recurrence despite aggressive initial management. Despite this, with successful salvage surgery DSS is excellent.

A Comprehensive Study on the Diagnosis and Management of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features.

Background: Since the noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTPs) was introduced in 2016, most retrospective studies have included cases diagnosed as encapsulated follicular variant of papillary thyroid carcinoma. We investigate a cohort diagnosed with NIFTP at resection. Methods: Retrospective institutional cohort of NIFTP from 2016 to 2022, including clinical, cytological, and molecular data for 319 cases (6.6% of thyroid surgeries, 183 cases as NIFTP-only). Results: The patient cohort had unifocal or multifocal thyroid nodules. Female:male ratio was 2.7:1, mean age was 52 years and median NIFTP size was 2.1 cm. NIFTP was associated with multiple nodules in 23% patients (n = 73) and 12% of NIFTP were multifocal (n = 39). Fine needle aspiration (FNA) of NIFTP (n = 255) were designated as nondiagnostic = 5%, benign = 13%, atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) = 49%, follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) = 17%, suspicious for malignancy = 12%, or malignant = 4%. Molecular alterations were identified in 93% (n = 114), RAS or RAS-like. Thyroid Imaging Reporting and Data System (TI-RADS) score 4 was recorded in 50% of NIFTP, followed by scores 3 and 5 (26% and 20%, respectively). We also investigated the factors associated with extent of surgery. In our NIFTP-only group (n = 183), 66% were identified after hemithyroidectomy (HT) and 34% after total thyroidectomy (TT). On univariate analysis, TT patients demonstrated higher Bethesda category by FNA, more often had aberrant preoperative thyroid function, and/or underwent an FNA of additional nodule(s). With multivariable regression, Bethesda V NIFTP, in the presence of other nodules being evaluated by FNA and aberrant preoperative thyroid function, independently predicts TT. Bethesda II NIFTP correlated significantly with HT. Fifty-two patients (28%) with NIFTP-only had at least one postoperative surveillance ultrasound. In the NIFTP-only cohort, no HT patients had completion thyroidectomy or received postoperative radioactive iodine. No recurrence or metastases were recorded with median follow-up of 35 months (6-76 months; n = 120). Conclusions: Given this large cohort of NIFTP, including a large subset of isolated NIFTP-only, some with >6 years of follow-up and no tumor recurrences, consensus practical guidelines are needed for adequate postoperative management. Given the American Thyroid Association (ATA) provides guidelines for management of low-risk malignancies, guidance regarding that for borderline/biologically uncertain tumors, including NIFTP, is a reasonable next step.

IDH2 -Mutated Sinonasal Tumors: A Review.

INTRODUCTION: Genetic profiling has caused an explosion in the subclassification of sinonasal malignancies. Distinguishing several of these tumor types by histomorphology alone has been quite challenging, and although pathologic classification aims to be as specific as possible, it remains to be seen if this recent move toward tumor speciation bears clinical relevance, most particularly focused on subtyping for the sake of prognostication and treatment. One such recently described cohort, predominantly lumped under the moniker of sinonasal undifferentiated carcinoma (SNUC) is IDH2 -mutated sinonasal carcinoma, a high-grade carcinoma associated with mutations in the isocitrate dehydrogenase-2 ( IDH2 ) gene. A hotspot mutation in the R172 codon has been described in 50% to 80% of the tumors classified as SNUC, large cell neuroendocrine carcinomas, and rarely in cases classified as olfactory neuroblastoma. The use of immunohistochemical and molecular approaches is required to correctly identify this subset of sinonasal tumors, with further study necessary to elucidate their unique pathophysiology, ultimately determining whether a revision is required toward the current therapeutic approach. AIMS: Here, we provide an overview of the IDH2- mutated sinonasal tumors, discuss histopathologic and clinical features, and focus on molecular diagnostics and novel immunohistochemical markers. RESULTS: A review of the literature reveals 82 reported cases with IDH2 -mutated sinonasal tumors (IST), confirmed either by molecular studies or diagnostic immunohistochemical markers. The mean patient age is 60 years (female/male: 1/1.4), the median tumor size is 5 cm (range: 2.5 to 7.0 cm), and the most common location is the nasal cavity (81%). IST displays tumor necrosis and increased mitotes. Histopathologically, IST shows SNUC-like, large cell neuroendocrine carcinomas-like, or poorly differentiated carcinoma-like features (77%, 12%, and 9%, respectively). The molecular hotspot alterations in mitochondrial IDH2 are: R172S (61%), R172T (19%), R172G (7%), and R172M (3%). Sixty-five percent of tumors are surgically resectable, and all patients received chemotherapy, radiation therapy, or both. Rates of locoregional recurrence and distant metastasis are 60% and 40%, respectively. One-, 3- and 5-year survival rates are 83%, 50%, and 43%, respectively. In all but 1 study, IST is associated with better outcomes than IDH2 wild-type tumors and SMARCB1 -deficient sinonasal tumors.

Clinicopathologic and Prognostic Features of Pediatric Follicular Cell-derived Thyroid Carcinomas: A Retrospective Study of 222 Patients.

Pediatric thyroid carcinomas (TCs) are rare and mainly approached based on data extrapolated from adults. We retrospectively reviewed 222 pediatric TCs (patient age less than or equal to 21 y). Lymph node (LN) disease volume at presentation was considered high if the largest positive LN measured ≥1 cm and/or >5 LNs were positive. High-grade follicular cell-derived thyroid carcinoma (HGFCTC) were defined by the presence of marked mitotic count and/or tumor necrosis and considered as high-risk histology along with papillary thyroid carcinomas (PTC) diffuse sclerosing variant (DSV). Disease-free survival (DFS) was analyzed. LN involvement at presentation was significantly associated with male sex, larger tumor size, lymphatic invasion, positive surgical margins, and distant metastases at presentation. Five- and 10-year DFS was 84% and 77%, respectively. Only 1 patient with HGFCTC died of disease. Within PTC variants, PTC-DSV was associated with adverse histopathologic parameters and higher regional disease spread, unlike PTC tall cell variant which did not portend worse behavior. The presence of necrosis conferred worse DFS ( P =0.006), while increased mitotic activity did not. While the entire HGFCTC group did not correlate with outcome ( P =0.071), HGFCTC with necrosis imparted worse DFS ( P =0.006). When restricted to PTC-DSV and HGFCTC with necrosis, high-risk histologic classification emerged as an independent prognostic parameter of DFS ( P =0.020). The excellent prognosis of pediatric TCs differs from that of adult TCs showing similar histologic features. While neither increased mitotic activity nor PTC tall cell variant histology predict adverse outcome, PTC-DSV and tumors with necrosis constitute high-risk histologic variants with an increased risk of protracted disease.

Prognostic impact of extranodal extension (ENE) in surgically managed treatment-naive HPV-positive oropharyngeal squamous cell carcinoma with nodal metastasis.

Extranodal extension (ENE) is a significant prognostic factor for human papilloma virus (HPV)-negative head and neck squamous cell carcinoma and is incorporated into AJCC 8th edition pN stage. It remains controversial whether ENE or the degree of ENE is prognostically relevant in HPV-positive oropharyngeal squamous cell carcinoma (OPSCC). A detailed clinicopathologic review was conducted in a large retrospective cohort of 232 surgically treated patients with HPV-positive OPSCC and nodal metastasis. Fifty-six patients (24%) had nodal metastasis with ENE. The median vertical extent of ENE was 2.9 mm (range 0.2-20.3 mm), and the median horizontal span of ENE was 2.5 mm (range: 0.3-14.0 mm). Comparing with patients without ENE, those with ENE were associated with a higher number of positive lymph nodes, lymphovascular invasion, perineural invasion, adjuvant chemotherapy, larger primary tumor size, and shorter follow up period. Patients with ENE had shortened overall survival (OS), disease specific survival (DSS), disease free survival (DFS), distant metastasis free survival (DMFS), and regional recurrence free survival (RRFS) on univariate survival analysis. The 5-year OS, DSS, and DFS were 95%, 97%, and 90% respectively for the group without ENE, and 64%, 71%, and 65% respectively for the group with ENE. On Multivariate survival analysis, the presence of ENE was an independent adverse prognostic factor for OS, DSS, and DFS. Additionally, major ENE defined as a vertical extent of ≥4 mm or irregular soft tissue deposit independently predicted shortened OS, DSS, and RFS. In conclusion, the presence of ENE, in particular major ENE, is an independent prognostic factor in HPV-positive OPSCC. Therefore, we propose to document the presence and extent of ENE for these tumors. Consideration may be given for AJCC 9th edition to include ENE into pN stage of HPV-positive OPSCC.

Head and Neck Acinic Cell Carcinoma: A New Grading System Proposal and Diagnostic Utility of NR4A3 Immunohistochemistry.

Acinic cell carcinoma (AciCC) is traditionally considered as a low-grade salivary gland carcinoma. However, a subset demonstrates high-grade features with a higher mortality rate and distant metastasis. In this large retrospective study of 117 cases, we aimed to establish a histologic grading scheme for AciCC. Adverse independent prognostic factors identified on the multivariate analysis included older age, tumor necrosis, nuclear anaplasia, lymphovascular invasion, absence of tumor-associated lymphoid stroma, and high American Joint Committee on Cancer (AJCC) pT and pN stages. A 3-tiered grading scheme using 4 pathologic parameters (mitotic index, necrosis, tumor border, and fibrosis at the frankly invasive front) was subsequently applied. Compared with low/intermediate-grade, high-grade AciCC defined as a mitotic index ≥5/10 HPFs and/or necrosis was an independently adverse prognostic factor. The 5-year overall survival was 50% in high-grade AciCCs, and 100% in low-grade or intermediate-grade AciCCs. Compared with low-grade or intermediate-grade AciCC, high-grade tumors were associated with older age, larger tumor size, focal rather than diffuse zymogen granules, solid architecture, infiltrative tumor border, fibrosis at the frankly invasive front, lymphovascular invasion, perineural invasion, positive margin, high pT, and pN stages. NR4A3 was a highly sensitive and specific immunohistochemical stain for diagnosing AciCC with a sensitivity and specificity of 96% and 93%, respectively. In conclusion, although we proposed a 2-tiered grading system for AciCC with high-grade tumors defined by a mitotic count ≥5/10 HPFs and/or necrosis, more studies are needed to assess the prognostic value of intermediate grade. NR4A3 immunohistochemical stain is a useful diagnostic marker for AciCC.

International Medullary Thyroid Carcinoma Grading System: A Validated Grading System for Medullary Thyroid Carcinoma.

PURPOSE: Medullary thyroid carcinoma (MTC) is an aggressive neuroendocrine tumor (NET) arising from the calcitonin-producing C cells. Unlike other NETs, there is no widely accepted pathologic grading scheme. In 2020, two groups separately developed slightly different schemes (the Memorial Sloan Kettering Cancer Center and Sydney grade) on the basis of proliferative activity (mitotic index and/or Ki67 proliferative index) and tumor necrosis. Building on this work, we sought to unify and validate an internationally accepted grading scheme for MTC. PATIENTS AND METHODS: Tumor tissue from 327 patients with MTC from five centers across the United States, Europe, and Australia were reviewed for mitotic activity, Ki67 proliferative index, and necrosis using uniform criteria and blinded to other clinicopathologic features. After reviewing different cutoffs, a two-tiered consensus grading system was developed. High-grade MTCs were defined as tumors with at least one of the following features: mitotic index ≥ 5 per 2 mm2, Ki67 proliferative index ≥ 5%, or tumor necrosis. RESULTS: Eighty-one (24.8%) MTCs were high-grade using this scheme. In multivariate analysis, these patients demonstrated decreased overall (hazard ratio [HR] = 11.490; 95% CI, 3.118 to 32.333; P < .001), disease-specific (HR = 8.491; 95% CI, 1.461 to 49.327; P = .017), distant metastasis-free (HR = 2.489; 95% CI, 1.178 to 5.261; P = .017), and locoregional recurrence-free (HR = 2.114; 95% CI, 1.065 to 4.193; P = .032) survivals. This prognostic power was maintained in subgroup analyses of cohorts from each of the five centers. CONCLUSION: This simple two-tiered international grading system is a powerful predictor of adverse outcomes in MTC. As it is based solely on morphologic assessment in conjunction with Ki67 immunohistochemistry, it brings the grading of MTCs in line with other NETs and can be readily applied in routine practice. We therefore recommend grading of MTCs on the basis of mitotic count, Ki67 proliferative index, and tumor necrosis.

Clinicopathologic Characteristics and Prognostic Factors of Primary and Recurrent Pleomorphic Adenoma: A Single Institution Retrospective Study of 705 Cases.

Although pleomorphic adenoma (PA) is benign, it may recur and prompt further treatment with radiotherapy (RT). This study investigated the prognostic features of primary and recurrent PAs. A total of 705 PAs (613 primary and 92 recurrent) were analyzed. The following parameters: age, site and size, status of resection, histologic features, and clinical management were documented and correlated with recurrence-free survival. For primary PAs: The mean patient age was 50 years (female/male: 2/1), the median size was 2.1 cm (range: 0.5 to 9.0 cm), and the most common location was the parotid (92%). Tumors showed the following: complete encapsulation (25%), involvement of the surrounding salivary gland/fat (74%), hypercellularity (26%), ≥10 pseudopods (15%), squamous metaplasia (43%), mitoses (49%), intravascular tumor deposit (n=1), close proximity to nerves (n=2), positive margin (15%), and suboptimal resection (2%). The recurrence rate was 3.4% and malignant transformation was <1%. On univariate analysis, age below 30, mitosis ≥3/10 HPFs, squamous metaplasia, hypercellularity, and suboptimal resection correlated with recurrence-free survival. On multivariate analysis, only age below 30, mitosis ≥3/10 HPF and suboptimal resection predicted recurrence. For recurrent PAs: The resected primary PAs were fragmented in 58%. Forty-eight percent of patients had subsequent recurrences, mostly within 10 years, and 1 patient developed a subsequent malignant transformation. Forty-two percent of patients received RT. On univariate analysis, only RT was associated with better outcome (P=0.033). Young age, high mitoses, and specimen integrity predicted recurrence in primary PA. Recurrent PAs are difficult to eradicate, and 48% of these recurred for the second time, mostly within 10 years.

Clinicopathologic features and outcome of head and neck mucosal spindle cell squamous cell carcinoma.

Spindle cell squamous cell carcinoma (SpC-SCC) is rare, accounting for 0.4-4% of head and neck (HN) SCCs. Better understanding of HN SpC-SCC clinicopathologic characteristics, especially features that predict outcome, is needed. We present a clinicopathologic review of 71 HN mucosal SpC-SCC from three tertiary centers. The patient population showed a median age of 63 years (range 20-91), slight male predominance (M:F = 1.6:1), and a preponderance of smokers/ex-smokers (45/71, 64%). Most lesions involved oral cavity (42/71, 59%), especially oral tongue (n = 18), and larynx (n = 20, 28%). Polypoid/exophytic growth and surface ulceration were seen in 60% and 86% of cases, respectively. Histologically, most tumors showed sarcoma-like pattern (65/70, 93%), the remaining exhibiting granulation tissue-like or fibromatosis-like patterns, and 5 lesions showed osteosarcomatous/chondrosarcomatous elements. Most tumors (53/71, 74%) showed a conventional SCC (C-SCC) component, keratinizing (86%) or non-keratinizing/basaloid (14%). Nodal metastases, seen in 22 (31%) of resection specimens, showed SpC-SCC and/or C-SCC histomorphology. By immunohistochemistry, 76% of lesions showed immunoreactivity for keratin and 62/60% of lesions were p40/p63 positive. Ki-67 proliferation index ranged from 5 to 70%. Follow-up was available on 69 patients, median of 1.1 years from the time of SpC-SCC diagnosis. The 3-, 5-, and 10-year disease-specific survival (DSS) was 62, 37, and 12%, respectively. AJCC pN stage was an independent prognostic factor for DSS and distant metastasis-free survival (DMFS), whereas the presence of C-SCC was independently associated with improved DMFS. HN SpC-SCC is rare and might be diagnostically challenging. AJCC pN stage and co-existing C-SCC component appear to be prognostically relevant.

Clinicopathologic Characteristics of Young Patients with Oral Squamous Cell Carcinoma.

Oral squamous cell carcinoma (OSCC) occasionally occurs in young patients and is likely to be distinct from OSCC in older patients. In this retrospective study, we described the clinicopathologic features and outcome of 150 OSCCs that were diagnosed in patients 40-year-old or younger. Most patients (63%) were non-smokers. The most common site of the primary tumor was oral tongue (n = 131, 87%), followed by gingiva (n = 9), buccal mucosa (n = 8) and lip (n = 2). The median patients' age at presentation was 34 (range: 16-40). Seven patients (5%) had Fanconi anemia with the gingiva being the most common location (4/7, 57%). All OSCCs were of keratinizing type. All cases tested for high-risk HPV (n = 34) were negative. On univariate analysis, high tumor budding was associated with decreased overall survival (OS) and distant metastasis free survival (DMFS), pattern of invasion correlated with OS and tumors with high stromal tumor infiltrating lymphocytes (sTIL) were associated with improved locoregional recurrence free survival (LRFS). Compared with patients 31 to 40-year-old, OSCC in the younger group was associated with significant less alcohol consumption (p = 0.011) and decreased DSS (p = 0.003) and DMFS (p = 0.023). On multivariate analysis, younger age (30 years or younger) was an independent prognostic factor for worse OS and DSS, whereas histologic grade was an independent prognostic factor for DSS. In summary, most OSCC in young patients occurred in non-smokers and did not occur in association with Fanconi anemia. Independent prognostic factors included age at presentation (30 years or younger) for OS and DSS, and histologic grade for DSS.