Acute Promyelocytic Leukemia With Torque Teno Mini Virus::RARA Fusion: An Approach to Screening and Diagnosis.

Acute promyelocytic leukemia (APL) with variant RARA translocation is linked to over 15 partner genes. Recent publications encompassing 6 cases have expanded the spectrum of RARA partners to torque teno mini virus (TTMV). This entity is likely underrecognized due to the lack of clinician and pathologist familiarity, inability to detect the fusion using routine testing modalities, and informatic challenges in its recognition within next-generation sequencing (NGS) data. We describe a clinicopathologic approach and provide the necessary tools to screen and diagnose APL with TTMV::RARA using existing clinical DNA- or RNA-based NGS assays, which led to the identification of 4 cases, all without other known cytogenetic/molecular drivers. One was identified prospectively and 3 retrospectively, including 2 from custom automated screening of multiple data sets (50,257 cases of hematopoietic malignancy, including 4809 acute myeloid leukemia/myeloid sarcoma/APL cases). Two cases presented as myeloid sarcoma, including 1 with multiple relapses after acute myeloid leukemia-type chemotherapy and hematopoietic stem cell transplant. Two cases presented as leukemia, had a poor response to induction chemotherapy, but achieved remission upon reinduction (including all-trans retinoic acid in 1 case) and subsequent hematopoietic stem cell transplant. Neoplastic cells demonstrated features of APL including frequent azurophilic granules and dim/absent CD34 and HLA-DR expression. RARA rearrangement was not detected by karyotype or fluorescent in situ hybridization. Custom analysis of NGS fusion panel data identified TTMV::RARA rearrangements and, in the prospectively identified case, facilitated monitoring in sequential bone marrow samples. APL with TTMV::RARA is a rare leukemia with a high rate of treatment failure in described cases. The diagnosis should be considered in leukemias with features of APL that lack detectable RARA fusions and other drivers, and may be confirmed by appropriate NGS tests with custom informatics. Incorporation of all-trans retinoic acid may have a role in treatment but requires accurate recognition of the fusion for appropriate classification as APL.

Discerning clinicopathological features of congenital neutropenia syndromes: an approach to diagnostically challenging differential diagnoses.

The congenital neutropenia syndromes are rare haematological conditions defined by impaired myeloid precursor differentiation or function. Patients are prone to severe infections with high mortality rates in early life. While some patients benefit from granulocyte colony-stimulating factor treatment, they may still face an increased risk of bone marrow failure, myelodysplastic syndrome and acute leukaemia. Accurate diagnosis is crucial for improved outcomes; however, diagnosis depends on familiarity with a heterogeneous group of rare disorders that remain incompletely characterised. The clinical and pathological overlap between reactive conditions, primary and congenital neutropenias, bone marrow failure, and myelodysplastic syndromes further clouds diagnostic clarity.We review the diagnostically useful clinicopathological and morphological features of reactive causes of neutropenia and the most common primary neutropenia disorders: constitutional/benign ethnic neutropenia, chronic idiopathic neutropenia, cyclic neutropenia, severe congenital neutropenia (due to mutations in ELANE, GFI1, HAX1, G6PC3, VPS45, JAGN1, CSF3R, SRP54, CLPB and WAS), GATA2 deficiency, Warts, hypogammaglobulinaemia, infections and myelokathexis syndrome, Shwachman-Diamond Syndrome, the lysosomal storage disorders with neutropenia: Chediak-Higashi, Hermansky-Pudlak, and Griscelli syndromes, Cohen, and Barth syndromes. We also detail characteristic cytogenetic and molecular factors at diagnosis and in progression to myelodysplastic syndrome/leukaemia.

IgG4-related lymphadenopathy.

IgG4-related lymphadenopathy is a nodal manifestation of IgG4-related disease (IgG4RD) which is characterized by increased polytypic IgG4+ plasma cells and IgG4+/IgG+ plasma cell ratio in lymph nodes and morphologically manifested as various patterns of reactive lymphadenopathy: Castleman disease-like, follicular hyperplasia, interfollicular expansion, progressive transformation of germinal centers and inflammatory pseudotumor-like. It typically presents with solitary or multiple, mild to moderate lymph node enlargement in otherwise asymptomatic patients. The serum IgG4 level is frequently elevated but C-reactive protein often remains normal. In patients not having a history of IgG4RD or manifestation of extranodal IgG4RD, a diagnosis of IgG4-lymphadenopathy should only be made with great caution given the non-specific morphologic features that can overlap with ANCA-associated vasculitis, interleukin-6 syndromes, Rosai-Dorfman disease, inflammatory myofibroblastic tumor, syphilis, lymphoma, and plasma cell neoplasia. Elevated IgG4 parameters, appropriate morphologies, and clinical correlation are essential to make the diagnosis of IgG4-lymphadenopathy more specific and clinically meaningful.

Inherited bone marrow failure syndromes and germline predisposition to myeloid neoplasia: A practical approach for the pathologist.

The diagnostic work up and surveillance of germline disorders of bone marrow failure and predisposition to myeloid malignancy is complex and involves correlation between clinical findings, laboratory and genetic studies, and bone marrow histopathology. The rarity of these disorders and the overlap of clinical and pathologic features between primary and secondary causes of bone marrow failure, acquired aplastic anemia, and myelodysplastic syndrome may result in diagnostic uncertainty. With an emphasis on the pathologist's perspective, we review diagnostically useful features of germline disorders including Fanconi anemia, Shwachman-Diamond syndrome, telomere biology disorders, severe congenital neutropenia, GATA2 deficiency, SAMD9/SAMD9L diseases, Diamond-Blackfan anemia, and acquired aplastic anemia. We discuss the distinction between baseline morphologic and genetic findings of these disorders and features that raise concern for the development of myelodysplastic syndrome.

Immunoglobulin G4-Related Disease, Lymphadenopathy, and Lymphoma: Histopathologic Features and Diagnostic Approach.

Lymphadenopathy occurring in patients with immunoglobulin G4 (IgG4)-related disease, termed IgG4-related lymphadenopathy, shows morphologic heterogeneity and overlap with other nonspecific causes of lymphadenopathy including infections, immune-related disorders, and neoplasms. This review describes the characteristic histopathologic features and diagnostic approach to IgG4-related disease and IgG4-related lymphadenopathy, with comparison to nonspecific causes of increased IgG4-positive plasma cells in lymph nodes, and with emphasis on distinction from IgG4-expressing lymphoproliferative disorders.

Polyclonal PAX8 expression in carcinomas of the biliary tract - Frequent non-specific staining represents a potential diagnostic pitfall.

Paired box protein 8 (PAX8) is a transcription factor that is considered a relatively specific marker of carcinomas of the thyroid, kidney, and Müllerian/Wolffian duct derivatives. Unexpected PAX8 immunoreactivity has occasionally been reported in other tumors. The frequency of PAX8 expression in carcinomas of the biliary tract is not well studied. We evaluated the immunohistochemical expression of PAX8 in 73 cases of biliary tract carcinoma. We found that 28 of 73 (38%) biliary tract carcinomas had variable immunoreactivity for PAX8, assessed by a widely used polyclonal antibody (ProteinTech Group, Chicago, IL). This included 3 (4%) of cases with strong diffuse, and 14 (19%) of cases with strong focal staining. Strong PAX8 expression was more frequent in distal bile duct carcinomas than other biliary sites (p = 0.015), and showed a weak association with advanced T stage (T3-T4 versus T1-T2; p = 0.09). No correlation was observed between PAX8 positivity and age at diagnosis, gender, or lymph node metastasis. The 28 polyclonal PAX8-positive cases were largely negative for monoclonal PAX8 and PAX6 immunostains, with only rare tumor cells with weak immunoreactivity being present in a subset of cases. We show that a substantial fraction of biliary tract carcinomas exhibit immunoreactivity with a widely used polyclonal PAX8 antibody. Pathologists should be aware of this potential pitfall during the diagnostic workup of hepatobiliary lesions to avoid misdiagnosis as a metastasis from a PAX8-positive tumor.

CD56 expression in basaloid anal squamous cell carcinoma - A potential diagnostic pitfall.

Anal squamous cell carcinoma (SqCC) is a morphologically heterogeneous entity. Basaloid and non-keratinizing anal SqCC may be confused with other tumors including neuroendocrine carcinoma due to morphologic overlap, and expression of neuroendocrine markers is not well-studied in anal SqCC. Prompted by a case of anal SqCC that was initially misdiagnosed as neuroendocrine carcinoma on the basis of morphology and CD56 expression, we retrospectively examined the expression of neuroendocrine markers CD56, synaptophysin, and chromogranin in 48 cases of basaloid anal SqCC, with clinicopathologic correlation. HPV16 was identified in 46 cases, HPV33 in one case, and one case was HPV-negative. Three (6.3%) cases demonstrated CD56 expression, including two with diffuse and one with focal expression. Two CD56-positive cases demonstrated basaloid morphology with peripheral palisading and the other demonstrated adenoid cystic/cylindroma-like morphology. None of the cases showed significant synaptophysin or chromogranin expression. The three cases expressing CD56 were HPV16-positive, and one demonstrated a CTNNB1 mutation. There was no difference in clinicopathologic features including stage, outcome, or HPV status, between CD56-positive and negative groups. Our findings support that CD56 expression is infrequently expressed in anal SqCC and is not indicative of neuroendocrine differentiation in the absence of expression of more specific neuroendocrine markers such as synaptophysin and chromogranin. Pathologists should be aware that CD56 expression may occur in basaloid anal SqCC and is a diagnostic pitfall due to morphologic overlap with neuroendocrine carcinoma and other tumors including basal cell carcinoma.

Outcomes After Stereotactic Body Radiation Therapy as a Bridging Modality to Liver Transplantation for Hepatocellular Carcinoma.

PURPOSE: For patients with hepatocellular carcinoma awaiting liver transplantation (LT), stereotactic body radiation therapy (SBRT) has emerged as a bridging treatment to ensure patients maintain priority status and eligibility per Milan criteria. In this study, we aimed to determine the efficacy and safety of SBRT in such situations. METHODS AND MATERIALS: A retrospective analysis was conducted of the outcomes of 27 patients treated with SBRT who were listed for LT at 1 institution. Among these, 20 patients with 26 tumors went on to LT and were the focus of this study. Operative reports and postoperative charts were evaluated for potential radiation-related complications. The explant pathology findings were correlated with equivalent dose in 2 Gy fractions and tumor size. RESULTS: Median pretreatment tumor size was 3.05 cm. Median total dose of radiation was 50 Gy delivered in 5 fractions. Pathologic complete response (pCR) was achieved in 16 tumors (62%). Median interval from end of SBRT to transplant was 287 days. Of the 21 tumors imaged before transplant, 16 or 76% demonstrated a clinical complete response based on modified Response Evaluation Criteria in Solid Tumors criteria. There was no significant correlation between pCR rate and increasing tumor size (odds ratio [OR], 0.95; 95% confidence interval, 0.595-1.53) or pCR rate and equivalent dose in 2 Gy fractions (OR, 1.03; 95% confidence interval, 0.984-1.07.) No patients experienced radiation-related operative or postoperative complications. Of the 27 patients who were listed for transplant, the dropout rate was 22%. Two of the 5 patients with Child-Pugh score 10 died of liver failure. CONCLUSIONS: These data demonstrate that SBRT as a bridging modality is a feasible option, with a pCR rate comparable to that of other bridging modalities and no additional radiation-related operative or postoperative complications. There was no dose dependence nor size dependence for pCR rate, which may indicate that for the tumor sizes in this study, the radiation doses delivered were sufficiently high.

Molecular and immunophenotypic characterization of anal squamous cell carcinoma reveals distinct clinicopathologic groups associated with HPV and TP53 mutation status.

Squamous cell carcinoma (SqCC) is the most common malignancy of the anal canal, where it is strongly associated with HPV infection. Characteristic genomic alterations have been identified in anal SqCC, but their clinical significance and correlation with HPV status, pathologic features, and immunohistochemical markers are not well established. We examined the molecular and clinicopathologic features of 96 HPV-positive and 20 HPV-negative anal SqCC. HPV types included 89 with HPV16, 2 combined HPV16/HPV18, and 5 HPV33. HPV-positive cases demonstrated frequent mutations or amplifications in PIK3CA (30%; p = 0.027) or FBXW7 mutations (10%). HPV-negativity was associated with frequent TP53 (53%; p = 0.00001) and CDKN2A (21%; p = 0.0045) mutations. P16 immunohistochemistry was positive in all HPV-positive cases and 3/20 HPV-negative cases (p < 0.0001; sensitivity: 100%; specificity: 85%) and was associated with basaloid morphology (p = 0.0031). Aberrant p53 immunohistochemical staining was 100% sensitive and specific for TP53 mutation (p < 0.0001). By the Kaplan-Meier method, HPV-negativity, aberrant p53 staining, and TP53 mutation were associated with inferior overall survival (OS) (p < 0.0001, p = 0.0103, p = 0.0103, respectively) and inferior recurrence-free survival (p = 0.133, p = 0.0064, and p = 0.0064, respectively). TP53/p53 status stratified survival probability by HPV status (p = 0.013), with HPV-negative/aberrant p53 staining associated with the worst OS, HPV-positive/wild-type p53 with best OS, and HPV-positive/aberrant p53 or HPV-negative/wild-type p53 with intermediate OS. On multivariate analysis HPV status (p = 0.0063), patient age (p = 0.0054), T stage (p = 0.039), and lymph node involvement (p = 0.044) were independently associated with OS. PD-L1 expression (CPS ≥ 1) was seen in 30% of HPV-positive and 40% of HPV-negative cases, and PD-L1 positivity was associated with a trend toward inferior OS within the HPV-negative group (p = 0.064). Our findings suggest that anal SqCC can be subclassified into clinically, pathologically, and molecularly distinct groups based on HPV and TP53 mutation status, and p16 and p53 immunohistochemistry represent a clinically useful method of predicting these prognostic groups.

IgG4-related Lymphadenopathy: A Comparative Study of 41 Cases Reveals Distinctive Histopathologic Features.

Lymphadenopathy is common in patients with immunoglobulin G4-related disease (IgG4-RD). However, the described histopathologic features of IgG4-related lymphadenopathy have been shown to be largely nonspecific. In an attempt to identify features specific for nodal IgG4-RD we examined the histopathologic features of lymph nodes from 41 patients with established IgG4-RD, with comparison to 60 lymph nodes from patients without known or subsequent development of IgG4-RD. An increase in immunoglobulin (Ig) G4-positive plasma cells >100/HPF and IgG4/IgG ratio >40% was identified in 51% of IgG4-RD cases and 20% of control cases. Localization of increased IgG4-positive plasma cells and IgG4/IgG ratio to extrafollicular zones was highly associated with IgG4-RD, particularly when identified in regions of nodal fibrosis (P<0.0001; specificity: 98.3%), or in the context of marked interfollicular expansion (P=0.022; specificity: 100%). Other features characteristic of IgG4-RD included frequent eosinophils associated with IgG4-positive plasma cells, phlebitis (P=0.06), and perifollicular granulomas (P=0.16). The presence of an isolated increase in intrafollicular IgG4-positive plasma cells and IgG4/IgG ratio was more frequently present in control cases than IgG4-RD (P<0.0001). This study confirms that increased IgG4-positive plasma cells and IgG4/IgG ratio are neither sensitive nor specific for the diagnosis of IgG4-related lymphadenopathy, and most described morphologic patterns are nonspecific. In contrast, nodal involvement by IgG4-rich fibrosis akin to extranodal IgG4-RD or diffuse interfollicular expansion by IgG4-positive plasma cells are highly specific features of true IgG4-related lymphadenopathy. Our findings provide for a clinically meaningful approach to the evaluation of lymph nodes that will assist pathologists in distinguishing IgG4-related lymphadenopathy from its mimics.

CYLD mutation characterizes a subset of HPV-positive head and neck squamous cell carcinomas with distinctive genomics and frequent cylindroma-like histologic features.

Mutations in the tumor suppressor CYLD, known to be causative of cylindromas, were recently described in a subset of high-risk (hr) HPV-positive head and neck squamous cell carcinomas (HNSCC). Pathologic and genetic characterization of these CYLD-mutant carcinomas, however, remains limited. Here, we investigated whether CYLD mutations characterize a histopathologically and genomically distinct subset of hrHPV-positive HNSCC. Comprehensive genomic profiling via hybrid capture-based DNA sequencing was performed on 703 consecutive head and neck carcinomas with hrHPV sequences, identifying 148 unique cases (21%) harboring CYLD mutations. Clinical data, pathology reports, and histopathology were reviewed. CYLD mutations included homozygous deletions (n = 61/148; 41%), truncations (n = 52; 35%), missense (n = 26; 18%) and splice-site (n = 9; 6%) mutations, and in-frame deletion (n = 1; 1%). Among hrHPV-positive HNSCC, the CYLD-mutant cohort showed substantially lower tumor mutational burden than CYLD-wildtype cases (n = 555) (median 2.6 vs. 4.4 mut/Mb, p < 0.00001) and less frequent alterations in PIK3CA (11% vs. 34%, p < 0.0001), KMT2D (1% vs. 16%, p < 0.0001), and FBXW7 (3% vs. 11%, p = 0.0018). Male predominance (94% vs. 87%), median age (58 vs. 60 years), and detection of HPV16 (95% vs. 89%) were similar. On available histopathology, 70% of CYLD-mutant HNSCC (98/141 cases) contained hyalinized material, consistent with basement membrane inclusions, within crowded aggregates of tumor cells. Only 7% of CYLD-wildtype cases demonstrated this distinctive pattern (p < 0.0001). Histopathologic patterns of CYLD-mutant HNSCC lacking basement membrane inclusions included nonkeratinizing (n = 22, 16%), predominantly nonkeratinizing (nonkeratinizing SCC with focal maturation; n = 10, 7%), and keratinizing (n = 11, 8%) patterns. The latter two groups showed significantly higher frequency of PTEN alterations compared with other CYLD-mutant cases (38% [8/21] vs. 7% [8/120], p = 0.0004). Within our cohort of hrHPV-positive HNSCCs, CYLD mutations were frequent (21%) and demonstrated distinctive clinical, histopathologic, and genomic features that may inform future study of prognosis and treatment.

Extramedullary Acute Myeloid Leukemia of the Renal Pelvis: Insights into a Visceral Niche.

Acute myeloid leukemia (AML) is a stem cell malignancy that originates in the bone marrow and involves the peripheral blood. Extramedullary AML is rarer, but it is most commonly associated with the former French-American-British (FAB) subtypes M4 or M5 of AML. AML cells may also home to the central nervous system and other solid organs such as cortical bone and skin. Such target sites of metastasis depend on microenvironmental niche interactions, which have not been fully elucidated to date. Visceral organs usually do not represent a favorable niche for AML stem cell occupancy. Herein, we describe the case of an 80-year-old man with extramedullary AML involvement of the renal pelvis. Hypercalcemia and obstructive uropathy were presenting features. The visceral niche is a rare site of involvement of myeloid malignancy, and hypercalcemia may reflect a mechanism of extramedullary involvement. We propose a treatment paradigm for this uncommon subset of AML based on advanced age and complex karyotype.

A deep learning diagnostic platform for diffuse large B-cell lymphoma with high accuracy across multiple hospitals.

Diagnostic histopathology is a gold standard for diagnosing hematopoietic malignancies. Pathologic diagnosis requires labor-intensive reading of a large number of tissue slides with high diagnostic accuracy equal or close to 100 percent to guide treatment options, but this requirement is difficult to meet. Although artificial intelligence (AI) helps to reduce the labor of reading pathologic slides, diagnostic accuracy has not reached a clinically usable level. Establishment of an AI model often demands big datasets and an ability to handle large variations in sample preparation and image collection. Here, we establish a highly accurate deep learning platform, consisting of multiple convolutional neural networks, to classify pathologic images by using smaller datasets. We analyze human diffuse large B-cell lymphoma (DLBCL) and non-DLBCL pathologic images from three hospitals separately using AI models, and obtain a diagnostic rate of close to 100 percent (100% for hospital A, 99.71% for hospital B and 100% for hospital C). The technical variability introduced by slide preparation and image collection reduces AI model performance in cross-hospital tests, but the 100% diagnostic accuracy is maintained after its elimination. It is now clinically practical to utilize deep learning models for diagnosis of DLBCL and ultimately other human hematopoietic malignancies.

Frozen section diagnosis of gastrointestinal poorly cohesive and signet-ring cell adenocarcinoma: useful morphologic features to avoid misdiagnosis.

Frozen section examination of adenocarcinomas with poorly cohesive growth, including signet-ring cell carcinoma, is challenging. Due to their diffuse morphology, the tumor cells may be indistinct and difficult to distinguish from inflammatory or stromal cells. Misdiagnosis may result in significant adverse clinical outcome. We performed a detailed retrospective analysis of such cases to identify features that are helpful to avoid misdiagnosis at the time of frozen section. We reviewed the original frozen section slides from 50 patients with poorly cohesive carcinoma (PCC) including 32 with positive and 18 with negative frozen section slides. Tumor cells and inflammatory cells were evaluated for 17 distinct cytologic and nine architectural or stromal features. Features with 100% specificity and positive predictive value (PPV) for carcinoma included the presence of cells with a single distinct cytoplasmic mucin vacuole, focal gland formation, and perineural invasion. Features with high specificity, sensitivity, PPV, and negative predictive value (NPV) (all > 75%) included irregular nuclear contours, large nuclear size with many nuclei > 4× the size of a small lymphocyte, and disruption/obliteration of normal structures. Other features with high specificity and PPV (both ≥ 85%) but relatively low sensitivity and NPV-included crescent-shaped/indented nuclei, prominent nucleoli, anisonucleosis (> 4:1 difference in nuclear size), multinucleation, and the presence of mitotic figures. We characterized useful histologic features of poorly cohesive carcinoma that may serve to distinguish carcinoma cells from benign inflammatory or stroma cells. Knowledge of the relatively specific features in particular may help surgical pathologists avoid false-negative interpretation resulting in significant clinical morbidity.

LGR5 in Barrett's Esophagus and its Utility in Predicting Patients at Increased Risk of Advanced Neoplasia.

INTRODUCTION: The expression of LGR5, a known stem cell marker, is poorly understood in Barrett's esophagus (BE) and related neoplasia. The aim of this study was to evaluate LGR5 in BE and related neoplasia and to evaluate its utility as a potential biomarker of progression to advanced neoplasia. METHODS: We evaluated total 137 patients, including 119 with BE and 18 with normal gastroesophageal mucosa for expression of LGR5 using RNA in situ hybridization; this also included 28 progressors and 30 nonprogressors. The LGR5 stain was evaluated using 1 qualitative and 2 quantitative parameters, using manual and automated platforms. RESULTS: Surface LGR5 expression was mainly seen in high-grade dysplasia (12/18) compared with low-grade dysplasia (1/8) and nondysplastic BE (0/17) (P < 0.0001). In contrast to nondysplastic BE, low- and high-grade dysplasia showed a higher percentage of mean number of LGR5-positive crypts per patient (P < 0.0001) and an increase in the mean number of LGR5 transcripts per cell (P < 0.0001). The mean percentage of LGR5-positive crypts per patient and the mean number of LGR5 transcripts per cell were also significantly higher in nondysplastic BE from progressor compared with nonprogressor (P < 0.0001, P = 0.014). The sensitivity and specificity of LGR5 for distinguishing progressor from nonprogressor were 50% and 87%, respectively. DISCUSSION: BE-related advanced neoplasia shows an expansion of the LGR5-positive cellular compartment, supporting its role as a stem cell marker in this disease. Quantitative LGR5 expression and surface epithelial reactivity are novel biomarkers of increased risk of progression to advanced neoplasia in BE.