Defining the Nature and Clinicopathologic Significance of Mallory-Denk-like Inclusions in Ovarian Fibromas: A Potential Degenerative Phenomenon Associated With Torsion.

Mallory-Denk bodies (MBD), described in alcoholic hepatitis, are composed of intermediate filaments admixed with other proteins. These cytoplasmic inclusions are irregularly shaped and eosinophilic as seen under the light microscope. MBD-like inclusions have rarely been described outside the hepatobiliary tree. Though rare, intracytoplasmic inclusions have been reported in ovarian fibromas. This study evaluates a series of torsed ovarian fibromas with intracytoplasmic inclusions resembling MDBs. Forty-three ovarian fibromas were retrieved from the pathology archives. The H&E slides were evaluated for the presence of MBD-like inclusions and histologic evidence of torsion. The cases with histologic features of torsion were included in the study group while the nontorsed fibromas formed the control group. Among the 15 cases of fibromas with torsion, MBD-like intracytoplasmic inclusions were seen in 5 cases, predominantly in the interface between necrotic areas and viable stroma. None of the cases from the control group showed any inclusions. There was no significant difference in the size of the fibroma or patient demographics between cases with and without inclusions. The inclusions were positive for cytokeratin and ubiquitin while being negative for per acidic Schiff and periodic acid-Schiff with diastase reaction, in the 3 cases selected for immunohistochemistry and special stains. Electron microscopy of the index case revealed a predominance of type 3 Mallory hyaline. This is the first report describing MDB-like inclusions in ovarian fibromas. These MDB-like inclusions appear to be limited to a fraction of ovarian fibromas that underwent torsion, suggesting that these inclusions likely result from subacute hypoxic damage to the cells.

Pancreatoblastomas and mixed and pure acinar cell carcinomas share epigenetic signatures distinct from other neoplasms of the pancreas.

Pancreatic neoplasms are heterogenous and have traditionally been classified by assessing their lines of cellular differentiation using histopathologic methods, particularly morphologic and immunohistochemical evaluation. These methods frequently identify overlapping differentiation along ductal, acinar, and neuroendocrine lines, raising diagnostic challenges as well as questions regarding the relationship of these neoplasms. Neoplasms with acinar differentiation, in particular, frequently show more than one line of differentiation based on immunolabeling. Genome methylation signatures, in contrast, are better conserved within cellular lineages, and are increasingly used to support the classification of neoplasms. We characterized the epigenetic relationships between pancreatoblastomas, acinar cell carcinomas (including mixed variants), pancreatic neuroendocrine tumors, solid pseudopapillary neoplasms, and pancreatic ductal adenocarcinomas using a genome-wide array platform. Using unsupervised learning approaches, pancreatic neuroendocrine tumors, solid pseudopapillary neoplasms, ductal adenocarcinomas, and normal pancreatic tissue samples all localized to distinct clusters based on their methylation profiles, whereas all neoplasms with acinar differentiation occupied a broad overlapping region located between the predominantly acinar normal pancreatic tissue and ductal adenocarcinoma clusters. Our data provide evidence to suggest that acinar cell carcinomas and pancreatoblastomas are similar at the epigenetic level. These findings are consistent with genomic and clinical observations that mixed acinar neoplasms are closely related to pure acinar cell carcinomas rather than to neuroendocrine tumors or ductal adenocarcinomas.

DNAJB1-PRKACA fusions occur in oncocytic pancreatic and biliary neoplasms and are not specific for fibrolamellar hepatocellular carcinoma.

Recently discovered DNAJB1-PRKACA oncogenic fusions have been considered diagnostic for fibrolamellar hepatocellular carcinoma. In this study, we describe six pancreatobiliary neoplasms with PRKACA fusions, five of which harbor the DNAJB1-PRKACA fusion. All neoplasms were subjected to a hybridization capture-based next-generation sequencing assay (MSK-IMPACT), which enables the identification of sequence mutations, copy number alterations, and selected structural rearrangements involving ≥410 genes (n = 6) and/or to a custom targeted, RNA-based panel (MSK-Fusion) that utilizes Archer Anchored Multiplex PCR technology and next-generation sequencing to detect gene fusions in 62 genes (n = 2). Selected neoplasms also underwent FISH analysis, albumin mRNA in-situ hybridization, and arginase-1 immunohistochemical labeling (n = 3). Five neoplasms were pancreatic, and one arose in the intrahepatic bile ducts. All revealed at least focal oncocytic morphology: three cases were diagnosed as intraductal oncocytic papillary neoplasms, and three as intraductal papillary mucinous neoplasms with mixed oncocytic and pancreatobiliary or gastric features. Four cases had an invasive carcinoma component composed of oncocytic cells. Five cases revealed DNAJB1-PRKACA fusions and one revealed an ATP1B1-PRKACA fusion. None of the cases tested were positive for albumin or arginase-1. Our data prove that DNAJB1-PRKACA fusion is neither exclusive nor diagnostic for fibrolamellar hepatocellular carcinoma, and caution should be exercised in diagnosing liver tumors with DNAJB1-PRKACA fusions as fibrolamellar hepatocellular carcinoma, particularly if a pancreatic lesion is present. Moreover, considering DNAJB1-PRKACA fusions lead to upregulated protein kinase activity and that this upregulated protein kinase activity has a significant role in tumorigenesis of fibrolamellar hepatocellular carcinoma, protein kinase inhibition could have therapeutic potential in the treatment of these pancreatobiliary neoplasms as well, once a suitable drug is developed.

Colorectal carcinoma with double somatic mismatch repair gene inactivation: clinical and pathological characteristics and response to immune checkpoint blockade.

Double somatic mismatch-repair-gene mutation/alteration is a recently recognized molecular mechanism that underlies microsatellite instability-high in some colorectal carcinomas. It remains to be determined whether and how microsatellite instability-high tumors with this molecular defect differ from their counterparts caused by other mechanisms, specifically, Lynch syndrome-associated and MLH1-promoter hypermethylated. In this study, we evaluated the clinical and pathological characteristics of a series of 15 double somatic mutation/alteration-associated microsatellite instability-high colorectal carcinomas identified from our genetics service and 68 such cases reported in the literature. We observed that these cases presented at an age similar to MLH1-promoter hypermethylated (n = 20) and microsatellite-stable (n = 39) cases but older than Lynch syndrome-associated cases (n = 20, p < 0.05). While these tumors simulated other microsatellite instability-high tumors in their prevalent right-sided location, they appeared to differ in TNM stages at presentation (73% stage III/IV versus 25% stage III/IV in other microsatellite instability-high tumors, p = 0.04). Histologically, 40% of them had a dominant solid growth pattern. Inter-tumoral heterogeneity was a striking feature, spanning the spectrum from medullary type (with a tumor-infiltrating-lymphocyte/high-power-field count as high as 59) to conventional-type with only few tumor-infiltrating-lymphocytes (1/high-power-filed). As a group, these tumors seemed less likely to show robustly high lymphocytic infiltration than other microsatellite instability-high tumors (only 20% had ≥10 tumor-infiltrating-lymphocytes/high-power-filed, whereas this rate in Lynch syndrome-associated and MLH1-promoter hypermethylated tumors was 60% and 75%, respectively). Three double somatic mutation/alteration-associated tumors were treated with a PD1/PD-L1 checkpoint inhibitor. While all three had an elevated tumor-mutation-burden (>47 mut/megabase), only one had tumor-infiltrating-lymphocytes >10/high-power-field, yet all three exhibited measurable response. In summary, microsatellite instability-high colorectal carcinomas caused by double somatic mismatch-repair-gene mutation/alteration may have varied clinical and pathological characteristics, and some may have relatively low tumor-infiltrating-lymphocytes; response to immune checkpoint inhibitors can be achieved in this group even when the lymphocytic infiltration is not abundant.

Cellular localization of PD-L1 expression in mismatch-repair-deficient and proficient colorectal carcinomas.

Blockade of the interaction between PD-1 and its ligands PD-L1 has shown clinical efficacy across several tumor types, especially in mismatch-repair-deficient colorectal carcinoma. The aim of this study was to examine the pattern and cellular localization of PD-L1 expression in the different molecular subtypes of mismatch-repair-deficient colorectal cancers vs. their mismatch-repair-proficient counterparts. PD-L1/SATB2 double-antibody-immunohistochemistry was utilized to distinguish tumor cell from immune cell staining. We observed in our series of 129 colorectal adenocarcinomas that PD-L1 expression occurred primarily in tumor-associated-immune cells and most prominently at the tumor-stroma-interface of the invasive front. The level of invasive front immune cell staining was significantly higher in mismatch-repair-deficient tumors compared to mismatch-repair-proficient tumors (p < 0.001), but no difference was observed among the different subtypes of mismatch-repair-deficient tumors: Lynch syndrome-associated vs. MLH1-methylated vs. unexplained. While selected mismatch-repair-proficient tumors exhibited unusually high tumor-infiltrating-lymphocytes and had high level immune cell PD-L1 expression, a positive correlation between PD-L1 expression and high lymphocyte count was detected only in mismatch-repair-deficient tumors (r = 0.39, p < 0.001) and not in mismatch-repair-proficient tumors. Notably, true tumor cell PD-L1 expression in colorectal carcinoma was rare, present in only 3 of 129 tumors (2.3%): 2 MLH1-methylated and 1 mismatch-repair-proficient with high tumor-infiltrating-lymphocytes; and the staining in the tumor cells in all 3 was diffuse (>=50% of the tumor). These findings may serve to inform further efforts aiming to evaluate PD-L1 immunohistochemistry vis-à-vis molecular sub-classification as predictive biomarkers in the treatment of colorectal carcinoma.

Loss of c-KIT expression in breast cancer correlates with malignant transformation of breast epithelium and is mediated by KIT gene promoter DNA hypermethylation.

KIT Proto-Oncogene Receptor Tyrosine Kinase (KIT) is a transmembrane receptor tyrosine kinase which plays an important role in regulation of cell proliferation, survival and migration. Interestingly, the role of c-KIT in malignant transformation seems to be highly tissue-specific and it can act either as an oncogene or tumor suppressor gene. Here we analyzed the expression of c-KIT in normal breast tissues and tissues from different stages encompassing major steps of breast tumor development. Our study showed, that the c-KIT protein expression is gradually lost during the process of breast tissue transformation. The analysis of previously published datasets revealed that c-KIT expression in breast malignancies was downregulated at mRNA level. Because sequencing studies did not identify any recurrent mutations or copy number alterations, we proposed a potential epigenetic mechanism for the downregulation of c-KIT expression. In-silico analysis of the KIT promoter revealed the presence of CpG islands, therefore we performed bisulfite sequencing of normal breast epithelial tissues as well as breast tumor samples. We found, that KIT promoter is hypermethylated in breast tumors compared to normal breast tissues. Furthermore, treatment of breast cancer cell lines, that lack the expression of c-KIT, with methyltransferase inhibitor 5-Azacytidine (5Aza-2dC) resulted in increased expression of c-KIT mRNA. Collectively, our studies demonstrate that c-KIT expression is epigenetically downregulated during breast epithelium transformation and cancer development via KIT promoter hypermethylation.

NTRK fusion oncogenes in pediatric papillary thyroid carcinoma in northeast United States.

BACKGROUND: An increase in thyroid cancers, predominantly papillary thyroid carcinoma (PTC), has been recently reported in children. METHODS: The histopathology of 28 consecutive PTCs from the northeast United States was reviewed. None of the patients (ages 6-18 years; 20 females, 8 males) had significant exposure to radiation. Nucleic acid from tumors was tested for genetic abnormalities (n = 27). Negative results were reevaluated by targeted next-generation sequencing. RESULTS: Seven of 27 PTCs (26%) had neurotrophic tyrosine kinase receptor (NTRK) fusion oncogenes (NTRK type 3/ets variant 6 [NTRK3/ETV6], n =5; NTRK3/unknown, n = 1; and NTRK type 1/translocated promoter region, nuclear basket protein [NTRK1/TPR], n = 1), including 5 tumors that measured >2 cm and 3 that diffusely involved the entire thyroid or lobe. All 7 tumors had lymphatic invasion, and 5 had vascular invasion. Six of 27 PTCs (22%) had ret proto-oncogene (RET) fusions (RET/PTC1, n = 5; RET/PTC3, n = 1); 2 tumors measured >2 cm and diffusely involved the thyroid, and 5 had lymphatic invasion, with vascular invasion in 2. Thirteen PTCs had the B-Raf proto-oncogene, serine/threonine kinase (BRAF) valine-to-glutamic acid mutation at position 600 (BRAF(V) (600E)) (13 of 27 tumors; 48%), 11 measured <2 cm, and 6 had lymphatic invasion (46%), with vascular invasion in 3. Fusion oncogene tumors, compared with BRAF(V) (600E) PTCs, were associated with large size (mean, 2.2 cm vs 1.5 cm, respectively; P = .05), solid and diffuse variants (11 of 13 vs 0 of 13 tumors, respectively; P < .001), and lymphovascular invasion (12 of 13 vs 6 of 13 tumors, respectively; P = .02); BRAF(V) (600E) PTCs were predominantly the classic variant (12 of 13 vs 1 of 13 tumors). Two tumors metastasized to the lung, and both had fusion oncogenes (NTRK1/TPR, n = 1; RET/PTC1, n = 1). CONCLUSIONS: Fusion oncogene PTC presents with more extensive disease and aggressive pathology than BRAF(V) (600E) PTC in the pediatric population. The high prevalence of the NTRK1/NTRK3 fusion oncogene PTCs in the United States is unusual and needs further investigation.

Essentials of macroscopic evaluation of specimens from gastrointestinal tract.

An astute macroscopic examination, coupled with correlating the gross findings with clinical indication and operative notes along with judicious, yet all pertinent sectioning for pathological examination is crucial for an accurate histopathological diagnosis, eventually leading to optimal patient care. This succinct review highlights the general concepts that lay the foundation of evaluating and grossing specimens from the luminal gastrointestinal (GI) tract. We also discuss the gross evaluation and sectioning of small therapeutic resections, along with a systematic approach and rationale when grossing and submitting histological sections from larger oncological resections from the luminal GI tract. Selected site-specific considerations, for example, grossing treated rectal and oesophageal cancers or taking sections from mucinous tumours of the appendix, among others, are also discussed.

Macroscopic examination of pathology specimens: a critical reappraisal.

Meticulous macroscopic examination of specimens and tissue sampling are crucial for accurate histopathology reporting. However, macroscopy has generally received less attention than microscopy and may be delegated to relatively inexperienced practitioners with limited guidance and supervision. This introductory paper in the minisymposium, Macroscopy Under the Microscope, focuses on issues regarding macroscopic examination and tissue sampling that have been insufficiently addressed in the published literature. It highlights the importance of specimen examination and sampling, discusses some general principles, outlines challenges and suggests potential solutions. It is critical to get macroscopy right the first time as it may not be possible to rectify errors even with expert histological assessment or to retrospectively collect missing data after the specimen retention period. Dissectors must, therefore, receive adequate guidance and supervision until they are proficient in macroscopic specimen examination. We emphasise the importance of the clinical context, optimal specimen fixation, succinct and clinically relevant macroscopic descriptions, macrophotography and judicious tissue sampling. We note that current recommendations based on the number of blocks to be submitted per maximum tumour dimension are ambiguous as the amount of tissue submitted in a cassette is not standardised and it is unclear whether 'block' refers to a tissue block or a paraffin block. Concerns around potential oversampling of 'therapeutic' specimens that could result in overdiagnosis due to detection of incidentalomas are also discussed. We hope that the issues discussed in this paper will engender debate on this clinically critical aspect of pathology practice.

Anal intraepithelial neoplasia: a review of terminology, differential diagnoses, and patient management.

Despite the knowledge of etiological association with high-risk human papilloma viruses and high-risk patient cohorts, the incidence of anal squamous cell carcinoma has continued to rise. The known precursor lesion (in particular, high-grade squamous intraepithelial lesion) makes it amenable to screening and surveillance strategies. However, the diagnosis of anal intraepithelial neoplasia suffers from interpretation challenges leading to high interobserver variability, along with numerous differential diagnoses and lingering terminology issues. Proper treatment of anal lesions requires accurate diagnosis, and while a variety of modalities are available for treatment, the rate of recurrence remains high and each modality has its own set of side effects and complications. The aim of this review article is to outline the diagnostic considerations and provide practical tips for diagnosing anal squamous intraepithelial lesions.

Ciliated foregut cysts involving the hepatopancreaticobiliary system: a clinicopathological evaluation with focus on atypical features.

AIMS: Foregut cystic malformations are rare developmental abnormalities, which may involve the hepatopancreaticobiliary tract (HPBT). These cysts are composed of inner ciliated epithelium; subepithelial connective tissue layer; smooth muscle layer; and an outer fibrous layer. While radiopathologic findings are often diagnostic, atypical location and histologic features can pose a diagnostic challenge. We aimed to study ciliated foregut cysts (CFCs) in the HPBT, assess their clinicopathological features with a focus on atypical features. METHODS: We collected cases of CFCs involving the HPBT from three large academic medical centres. H&E-stained slides and immunohistochemical stains (where available) were reviewed for each case. Relevant demographic, clinical and pathological information was collected from the medical records. RESULTS: 21 cases were identified. The median age was 53 years (range, 3-78 years). 17 cysts were identified within the liver (segment 4 was the most common location, n=10) and 4 in the pancreas. Cysts were mostly identified incidentally (n=13), abdominal pain was a common symptom (n=5). Cyst size ranged from 0.7 to 17.0 cm (median, 2.5 cm). Radiological findings were available in 17 cases. Cilia were identified in all cases. 19 of 21 cases demonstrated the presence of a smooth muscle layer (thickness, <0.1 mm to 3.0 mm). Three cases showed gastric metaplasia, while one case revealed additional low-grade dysplasia, with features similar to intraductal papillary neoplasm of the bile duct. CONCLUSIONS: We highlight clinicopathological features of CFCs in the HPBT. The histomorphology is usually straightforward; however, unusual location and atypical features can pose a diagnostic challenge.

Clinicopathological significance of neutrophil-rich colorectal carcinoma.

AIMS: The importance of the interaction between tumour cells and neutrophils has recently begun to emerge. However, the significance of tumour-infiltrating neutrophil (TIN) in colorectal carcinomas (CRCs) remains unclear. The aim of this study was to investigate the prognostic significance of TIN in CRCs. METHODS: CRCs were evaluated for TIN and were classified as neutrophil-rich (NR), neutrophil-intermediate (NI) and neutrophil-poor (NP) based on the presence of >15, 5-15 and <5 TIN per 100 tumour cells, respectively. Various clinicopathological parameters were recorded in each case including age, gender, histological grade, tumour, node, metastasis (TNM) stage, tumour location and DNA mismatch repair (MMR) status. RESULTS: Among the 348 CRC cases reviewed, 38 cases were NR, 43 cases were NI and 267 cases were NP. High TIN was associated with higher histological grade (p=0.0222), right-sided tumour location (p=0.0025), advanced TNM stage (p=0.0346) and higher rate of MMR-deficient CRCs (p=0.0027). Patients with NR CRCs had significantly poorer 5-year recurrence-free survival comparing to patients with NI or NP CRCs on Kaplan-Meier analysis (p=0.0001) and high TIN remained an independent risk factor with multivariate analysis (p=0.0137; HR: 1.930, 95% CI: 1.144 to 3.255). NR CRCs are more commonly seen in MMR-deficient than in MMR-proficient CRCs (p=0.0006). Patients with MMR-deficient NR CRCs showed similar 5-year recurrence-free survival compared with MMR-proficient NR CRCs. CONCLUSIONS: Our findings reveal that high TIN confers poorer patient prognosis in both MMR-proficient and MMR-deficient CRCs.

Metastatic Neoplasms Involving the Stomach.

OBJECTIVES: Metastatic neoplasms involving the stomach are rare and diagnostically challenging if clinical history of malignancy is absent or unavailable. This study was designed to identify the tumors that most frequently metastasize to the stomach and the morphologic features that can provide clues to investigate the possibility of metastasis and predict the primary sites. METHODS: All patients with metastatic neoplasms involving the stomach were included in the study. The H&E- and immunohistochemical-stained slides were reviewed, and all clinical, endoscopic, and radiologic information was recorded. RESULTS: One hundred fifty patients, including 84 (56%) women and 66 (44%) men (mean age, 64 years), were identified. Gastric metastases were the initial presentation in 15% cases. Epithelial tumors (73.3%) comprised the largest group, followed by melanoma (20.6%), sarcomas (4%), germ cell tumors (1.3%), and hematolymphoid neoplasms (0.7%). Lobular breast carcinoma was the most common neoplasm overall in women, while in men, it was melanoma. Solid/diffuse growth pattern (75%) was more common compared with glandular morphology. The solid/diffuse category included lobular breast carcinoma (21.3%), melanoma (20.6%), and renal cell carcinoma (10.6%), while the glandular category was dominated by gynecologic serous carcinomas (7.3%) with papillary/micropapillary architecture. CONCLUSIONS: Metastatic neoplasms should be considered in the differential diagnosis of gastric neoplasms, particularly those with a diffuse/solid growth pattern. Glandular neoplasms are difficult to differentiate from gastric primaries except for Müllerian neoplasms, which frequently show a papillary/micropapillary architecture.

Clinicopathologic Features of Gynecologic Malignancies Presenting Clinically as Colonic Malignancies.

OBJECTIVES: To systematically evaluate gynecologic malignancies (adnexal or uterine) causing gastrointestinal (GI) signs (eg, mass on colonoscopy) or symptoms (eg, bloody stools) clinically mimicking a GI primary malignancy. METHODS: The archives of 2 institutions were retrospectively reviewed for gynecologic malignancies clinically manifesting as colonic lesions. For each case, available radiologic, endoscopic, and histologic findings were recorded. RESULTS: We identified 16 cases: 13 biopsies and 3 resections. The masses were localized in the rectosigmoid (14 cases [88%]), right (1 case [6%]), and transverse (1 case [6%]) colon. Gastrointestinal-type complaints included abdominal pain, weight loss, hematochezia, and obstruction; 1 case was asymptomatic and found during screening colonoscopy. Nine patients (56%) had no known prior gynecologic malignancy, and in only 2 of these patients was there some clinical suspicion of a noncolonic primary malignancy. Most cases (13 [81%]) were serous carcinoma, usually high-grade adnexal or primary peritoneal. Six cases (38%) directly extended into the colon, and 7 (44%) metastasized; route of spread was unclear in the others. Only 1 case (6%) showed mucosal involvement, and none showed desmoplasia or dirty necrosis. Four of the 13 serous carcinomas (31%) showed psammoma bodies. CONCLUSIONS: Advanced gynecologic malignancies, most commonly serous carcinoma, can rarely manifest as GI lesions. Clues to noncolonic origin on biopsy include lack of colonic mucosal involvement/dysplasia, desmoplasia, or dirty necrosis.

Same-Cell Co-Occurrence of RAS Hotspot and BRAF V600E Mutations in Treatment-Naive Colorectal Cancer.

PURPOSE: Mitogen-activated protein kinase pathway-activating mutations occur in the majority of colorectal cancer (CRC) cases and show mutual exclusivity. We identified 47 epidermal growth factor receptor/BRAF inhibitor-naive CRC patients with dual RAS hotspot/BRAF V600E mutations (CRC-DD) from a cohort of 4,561 CRC patients with clinical next-generation sequencing results. We aimed to define the molecular phenotypes of the CRC-DD and to test if the dual RAS hotspot/BRAF V600E mutations coexist within the same cell. MATERIALS AND METHODS: We developed a single-cell genotyping method with a mutation detection rate of 96.3% and a genotype prediction accuracy of 92.1%. Mutations in the CRC-DD cohort were analyzed for clonality, allelic imbalance, copy number, and overall survival. RESULTS: Application of single-cell genotyping to four CRC-DD revealed the co-occurrence of both mutations in the following percentages of cells per case: NRAS G13D/KRAS G12C, 95%; KRAS G12D/NRAS G12V, 48%; BRAF V600E/KRAS G12D, 44%; and KRAS G12D/NRAS G13V, 14%, respectively. Allelic imbalance favoring the oncogenic allele was less frequent in CRC-DD (24 of 76, 31.5%, somatic mutations) compared with a curated cohort of CRC with a single-driver mutation (CRC-SD; 119 of 232 mutations, 51.3%; P = .013). Microsatellite instability-high status was enriched in CRC-DD compared with CRC-SD (23% v 11.4%, P = .028). Of the seven CRC-DD cases with multiregional sequencing, five retained both driver mutations throughout all sequenced tumor sites. Both CRC-DD cases with discordant multiregional sequencing were microsatellite instability-high. CONCLUSION: Our findings indicate that dual-driver mutations occur in a rare subset of CRC, often within the same tumor cells and across multiple tumor sites. Their presence and a lower rate of allelic imbalance may be related to dose-dependent signaling within the mitogen-activated protein kinase pathway.

An update on subtypes of hepatocellular carcinoma: From morphology to molecular.

The morphologic spectrum of hepatocellular carcinoma (HCC) is quite broad. While in about one-third of cases, the neoplasms can be categorized into meaningful subtypes based on morphology, a vast majority of these neoplasms are morphologically heterogeneous. With extensive tumor profiling, data has begun to emerge which can correlate specific morphologic features with underlying molecular signatures. A true morphologic subtype not only has reproducible H & E features, further supported by specific immunohistochemical or molecular signatures, but also has specific clinical implications and prognostic associations. Eight such morphologic subtypes are recognized by the 2019 WHO classification of tumors with a few more additional subtypes described in the literature. The goal of this review is to familiarize the reader with the morphologic subtypes and elaborate on the clinical and molecular associations of these neoplasms.

Incidental secondary findings in hemorrhoidectomy specimens: a 16-year experience from a single academic center.

Hemorrhoidectomy specimens serve as an excellent resource for study of incidental anal pathology. Detection of most incidental findings is quite rare, although diagnosing clinically significant lesions can have profound impact on the clinical follow-ups. While there are many case reports of incidental findings in hemorrhoidectomy specimens, there are few large studies focused on this topic. The aim of this study was to describe the spectrum and likelihood of detecting incidental findings in hemorrhoidectomy specimens. We reviewed all hemorrhoidectomy specimens that showed incidental clinically significant diagnoses over a 16-year period (2003-2019) for this study. Patient's age, sex, and significant clinical history (Human Immunodeficiency Virus (HIV) status, precursor lesions, other malignancy) were recorded from clinical notes. We identified incidental clinically significant findings in 72 of 1612 (4.5%) specimens. We identified 7 incidental malignancies (squamous cell carcinoma, verrucous carcinoma, adenocarcinoma, mixed adenocarcinoma and neuroendocrine carcinoma, poorly differentiated neuroendocrine carcinoma, melanoma), 54 anal intraepithelial neoplasias (AINs), and 11 benign findings (melanocytic lesions, colorectal polyps, angiokeratoma, infectious/inflammatory). Within the AIN group, the detection of low-grade squamous intraepithelial lesions (LSILs) remained steady; there was a recent, sustained rise in detection of high-grade squamous intraepithelial lesions (HSILs), with more cases showing HSILs (2.6%) than only LSILs (0.7%). In 72.2% of patients, the incidental secondary finding represented a first diagnosis for that entity in the anal canal. Thirty seven percent of patients with anal dysplasia in the hemorrhoidectomy specimen had a prior diagnosis of squamous dysplasia in the anogenital tract. Overall, significant incidental findings were detected in 4.5% (72/1612) of hemorrhoidectomies, supporting routine histological examination of these specimens.

Alterations in Ki67 Labeling Following Treatment of Poorly Differentiated Neuroendocrine Carcinomas: A Potential Diagnostic Pitfall.

Assessment of the Ki67 index is critical for grading well-differentiated neuroendocrine tumors (WD-NETs), which can show a broad range of labeling that defines the WHO grade (G1-G3). Poorly differentiated neuroendocrine carcinomas (PD-NECs) have a relatively high Ki67 index, >20% in all cases and commonly exceeding 50%. After anecdotally observing PD-NECs with an unexpectedly low and heterogeneous Ki67 index following chemotherapy in 5 cases, we identified 15 additional cases of treated high-grade neuroendocrine neoplasms (HG-NENs). The study cohort comprised 20 cases; 11 PD-NECs, 8 mixed adenoneuroendocrine carcinomas, and 1 WD-NET, G3 from various anatomic sites (gastrointestinal tract, pancreas, larynx, lung, and breast). The Ki67 index was evaluated on pretreatment (when available) and posttreatment samples. Topographic heterogeneity in the Ki67 index was expressed using a semi-quantitative score of 0 (no heterogeneity) to 5 (>80% difference between maximal Ki67 and minimal Ki67 indices). Relative to the pretreatment group (n=9, mean Ki67 of 86.3%, range 80% to 100%), the neoplasms in the posttreatment group (n=20, mean Ki67 of 47.7%, range 1% to 90%) showed a significantly lower Ki67 index (18/20 cases). Of the 18 cases with a relatively low Ki67 index, 15 showed heterogeneous labeling (mean heterogeneity score of 2.3, range 1 to 5) and in 3 cases it was a homogeneously low. This phenomenon was observed in all subtypes of HG-NENs. In 6 cases, the alterations in Ki67 index following treatment were sufficient to place these HG-NENs in the WHO G1 or G2 grade, erroneously suggesting a diagnosis of WD-NET, and in 9 cases there was sufficient heterogeneity in the Ki67 index to suggest that a limited biopsy may sample an area of low Ki67, even though hotspot regions with a Ki67 index of >20% persisted. In 7 cases, the alterations in the Ki67 index were accompanied by morphologic features resembling a WD-NET. These observations suggest that there is a potential for misinterpretation of previously treated PD-NECs as WD-NETs, or for assigning a lower grade in G3 WD-NETs. While the prognostic significance of treatment-associated alterations in Ki67 index is unknown, awareness of this phenomenon is important to avoid this diagnostic pitfall when evaluating treated NENs.

Discordant DNA mismatch repair protein status between synchronous or metachronous gastrointestinal carcinomas: frequency, patterns, and molecular etiologies.

The widespread use of tumor DNA mismatch repair (MMR) protein immunohistochemistry in gastrointestinal tract (GIT) carcinomas has unveiled cases where the MMR protein status differs between synchronous/metachronous tumors from the same patients. This study aims at examining the frequency, patterns and molecular etiologies of such inter-tumoral MMR discordances. We analyzed a cohort of 2159 colorectal cancer (CRC) patients collected over a 5-year period and found that 1.3% of the patients (27/2159) had ≥ 2 primary CRCs, and 25.9% of the patients with ≥ 2 primary CRCs (7/27) exhibited inter-tumoral MMR discordance. We then combined the seven MMR-discordant CRC patients with three additional MMR-discordant GIT carcinoma patients and evaluated their discordant patterns and associated molecular abnormalities. The 10 patients consisted of 3 patients with Lynch syndrome (LS), 1 with polymerase proofreading-associated polyposis (PAPP), 1 with familial adenomatous polyposis (FAP), and 5 deemed to have no cancer disposing hereditary syndromes. Their MMR discordances were associated with the following etiologies: (1) PMS2-LS manifesting PMS2-deficient cancer at an old age when a co-incidental sporadic MMR-proficient cancer also occurred; (2) microsatellite instability-driven secondary somatic MSH6-inactivation occurring in only one-and not all-PMS2-LS associated MMR-deficient carcinomas; (3) "compound LS" with germline mutations in two MMR genes manifesting different tumors with deficiencies in different MMR proteins; (4) PAPP or FAP syndrome-associated MMR-proficient cancer co-occurring metachronously with a somatic MMR-deficient cancer; and (5) non-syndromic patients with sporadic MMR-proficient cancers co-occurring synchronously/metachronously with sporadic MMR-deficient cancers. Our study thus suggests that inter-tumoral MMR discordance is not uncommon among patients with multiple primary GIT carcinomas (25.9% in patients with ≥ 2 CRCs), and may be associated with widely varied molecular etiologies. Awareness of these patterns is essential in ensuring the most effective strategies in both LS detection and treatment decision-making. When selecting patients for immunotherapy, MMR testing should be performed on the tumor or tumors that are being treated.

Piggyback mycosis: pulmonary hydatid cyst with a mycotic co-infection.

The lungs are common sites for the occurrence of saprophytic or invasive mycosis as well as hydatid cysts. The two diseases seldom coexist, and the manifestation is seen as a fungal ball (usually aspergilloma) formed in the cavity left behind after hydatid cystectomy. Active invasion and proliferation of the fungi in the laminated ectocyst or sometimes the pericyst of the hydatid is very unusual. We report such a unique coexistence identified in two of the six surgically excised pulmonary hydatid cysts in the past 2 years. Both were immunocompetent males, who had presented with non-specific symptoms of cough, haemoptysis and chest pain. The septate slender hyphae of the invading fungus resembled those of Aspergillus.