Treeck, Benjamin J. Van

AimThe aim of this study was to compare the histopathologic features of MMF‐induced colitis and colonic GVHD and develop a digital tool using deep learning convolutional neural networks (CNNs) to semi‐automate the quantification of eosinophils.MethodsMMF and GVHD colitis cases were retrieved. A cohort of transplant patients who were at risk for developing GVHD and were on MMF at the time of biopsy was also identified. Cases were reviewed for histologic features and a deep learning CNN was trained to quantify lamina propria eosinophils. Clinical history was collected.ResultsNinety‐five patients were included in the study group: GVHD (n = 37), MMF (n = 25) and GVHD vs. MMF (n = 33). Within the GVHD vs. MMF group, one patient was thought to have definitive MMF colitis and one possible MMF colitis. The GVHD group had a significantly higher apoptotic count compared to the MMF group (median: 7 vs. 2, P = 0.03). Neuroendocrine aggregates were present in the GVHD (N = 12) and GVHD vs. MMF (N = 4) groups while absent in the MMF group. The MMF group had a higher semi‐quantitative eosinophil score and a higher automated eosinophil count as detected by the deep learning CNN (median eos/HPF: MMF 19.2, GVHD vs. MMF 3.6, GVHD 3.4, P < 0.001).ConclusionsLower eosinophil counts, higher apoptotic counts and neuroendocrine cell aggregates favour the diagnosis of GVHD. AI models for eosinophil quantification may serve as an ancillary tool for assessing this differential diagnosis. Given the rarity of MMF‐induced colitis in SCT patients, pathologists should have a high threshold for making this diagnosis in this population.

Abstract Objectives Cirrhosis-like hepatocellular carcinoma (CL-HCC) is a rare hepatocellular malignancy characterized by multiple tumor nodules that clinically, radiologically, macroscopically, and microscopically mimic cirrhosis. We aimed to elucidate the molecular biology of CL-HCC and determine tumor nodule clonality. Methods We performed RNA sequencing on formalin-fixed, paraffin-embedded tissue from confirmed CL-HCC cases (n = 6), along with corresponding nonneoplastic hepatic tissue (n = 4) when available. Transcriptomes from our previous work on steatohepatitic hepatocellular carcinoma and The Cancer Genome Atlas (TCGA) were used for comparison purposes. Results Histologically, CL-HCC displayed innumerable nodules and extensive vascular invasion. Intratumoral nodule comparison indicated that the multiple nodules were all clonally related, not independent primaries. The unique histomorphologic appearance corresponded with a distinct transcriptome compared with other HCCs, including fibrolamellar HCC (n = 6), steatohepatitic HCC (n = 8), and conventional HCC in TCGA (n = 424). Tumor-normal gene expression analysis revealed consistent overexpression of several genes involved in degradation of tissue matrix. No recurrent translocations or point mutations were identified. CL-HCC showed a gene expression profile indicative of zone 2 hepatocytes. Conclusions CL-HCC’s distinctive clinicopathologic features correspond to a unique gene expression profile, increased expression of invasive markers, features of zone 2 hepatocytes, and features suggestive of intratumoral nodule monoclonality.

Malignant peripheral nerve sheath tumor (MPNST) is a rare aggressive type of sarcoma. The epithelioid variant of MPNST has a distinctive morphology and immunophenotype, which can be a diagnostic challenge when it arises in an unusual location. Awareness of these morphologic entities is essential to make an accurate diagnosis. Here, we report a case of epithelioid MPNST involving the liver. The tumor displayed rhabdoid morphology and an unusual immunophenotype. The report also discusses histopathologic features, molecular alterations, and the differential diagnoses of this rare entity.

Aims. Mucinous cystic neoplasms (MCNs) are cystic neoplasms with mucinous epithelium surrounded by ovarian-like stroma. Extraovarian MCN occurring in the liver and pancreas have been well characterized. However, only rare case reports of MCN arising outside of these locations have been reported. MCNs arising in unusual locations should enter the differential diagnosis of mucinous intra-abdominal tumors and must be distinguished from more common mimics. Therefore, we aimed to examine a series of MCNs of the retroperitoneum and mesentery to characterize the clinicopathologic features of this entity. Methods and results. Seven MCNs arising in the abdominal mesentery or retroperitoneum were retrospectively identified. A clinicopathologic, histologic, and immunohistochemical (keratin 7, keratin 19, keratin 20, calretinin, inhibin-α, steroidogenic factor-1 (SF-1), estrogen receptor (ER), progesterone receptor (PR), PAX8, CDX2, and CD10) analysis was performed. All 7 MCNs were from females with a median age of 41 years old and a median size of 8 cm. All cases demonstrated mucinous with or without concomitant non-mucinous epithelium overlying spindle cell ovarian-like stroma. Luteinized cells were noted. The epithelium was positive for keratin 7 and keratin 19 in all 7 cases, while the stroma expressed ER, PR, and SF-1 in all cases stained. Calretinin was focally positive in the stroma of 3 of 7 cases, while inhibin-α was focally expressed in 5 of 6 cases. Conclusions. These results highlight the clinicopathologic, histologic, and immunophenotypic similarities between MCNs of the mesentery, retroperitoneum, pancreas, and liver. Overlapping features suggest a common histogenesis for all MCNs, which could include periductal fetal mesenchyme, aberrant migration of primordial germ cells, or abnormal differentiation or metaplasia of the embryonic coelomic epithelium.

Abstract Introduction/Objective Mucinous cystic neoplasms (MCN) are neoplasms with mucinous epithelium surrounded by ovarian-type stroma, occurring in the pancreas and liver. Reports of MCN arising outside the liver and pancreas are rare. We aim to perform a clinicopathologic, morphologic and immunohistochemical analysis of mesenteric and retroperitoneal MCN arising separate from the pancreas and liver. Methods Seven mesenteric or retroperitoneal MCN (n=7) were identified and clinical and radiologic information obtained, where available. The following immunostains were performed on each case: keratin 7, keratin 19, estrogen receptor, progesterone receptor, calretinin, inhibin-α, and SF-1. Results All seven MCN were from women with a median age of 41 years (range: 28-70 years). The median size of the MCN was 8cm (range: 8-14.5 cm) involving the retroperitoneum (n=5) and mesoappendix (n=2). One patient was diagnosed with a synchronous right ovarian mucinous cystadenoma. Morphologically, all MCN displayed mucinous or mixed non-mucinous-mucinous cuboidal to columnar epithelium without dysplasia. Ovarian-type stroma was identified underlying the epithelium with foci of luteinized stromal cells. The ovarian-type stroma expressed estrogen and progesterone receptors in all seven cases, two cases stained with SF-1 showed diffuse strong stromal positivity, and one case stained with inhibin showed focal strong stromal positivity. Additional immunohistochemical analysis with CK7, CK19, calretinin, inhibin-α, and SF-1 on all cases is pending. Conclusion Clinicopathologic, morphologic, and immunohistochemical characteristics of mesenteric/retroperitoneal MCN are similar to their pancreas and liver counterparts. Familiarity with this entity and knowing it can arise in mesenteric/retroperitoneal locations is important for accurate diagnosis and to distinguish it from mucinous carcinoma, teratoma, endometriosis and other differential diagnoses which have different implications. We propose that mesenteric/retroperitoneal MCN may possibly arise from primordial germ cells that underwent aberrant migration during their retroperitoneal descent through the fetal dorsal mesentery which gives rise to the neck and body of the pancreas as well as the mesentery and mesoappendix.

Abstract Objectives Mucinous cystic neoplasm of the liver is characterized by neoplastic mucinous and/or biliary epithelium surrounded by ovarian-type stroma. Immunohistochemical studies have shown that the ovarian-type stroma expresses estrogen receptor, suggesting potential hormonal responsiveness. The molecular biology of mucinous cystic neoplasm of the liver remains poorly studied. Methods Transcriptome sequencing and immunohistochemistry were performed on a series of mucinous cystic neoplasms. Results Mucinous cystic neoplasm of the liver exhibited significantly increased RNA expression of ovarian stromal markers WT1, PR, and ER2 and sex cord stromal markers SF-1, inhibin-α, and calretinin compared with nonneoplastic liver. Immunohistochemistry confirmed the RNA-level data. Evidence for sex hormone biosynthesis was identified by significant overexpression of multiple estrogen biosynthetic enzymes. Expression of 17β-hydroxysteroid dehydrogenase 1 was confirmed immunohistochemically. Pathway analysis also identified significant upregulation of the hedgehog and Wnt pathways and significant downregulation of T-helper 1 and T-helper 2 pathways. Conclusions Mucinous cystic neoplasm of the liver recapitulates ovarian stroma at the morphologic, DNA, RNA, and protein levels. These data support the concept that this tumor likely arises from ectopic primitive gonadal tissue and/or stromal cells with capacity to transdifferentiate to ovarian cortical cells.

AbstractObjectivesSteatohepatitic hepatocellular carcinoma is a distinct variant of hepatocellular carcinoma strongly associated with underlying nonalcoholic steatohepatitis. The molecular biology of steatohepatitic hepatocellular carcinoma is not fully elucidated, and thus we aimed to investigate the molecular underpinnings of this entity.MethodsTranscriptomic analysis using RNAseq was performed on eight tumor-nonneoplastic pairs of steatohepatitic hepatocellular carcinoma with comparison to conventional hepatocellular carcinoma transcriptomes curated in The Cancer Genome Atlas. Immunohistochemistry was used to validate key RNA-level findings.ResultsSteatohepatitic hepatocellular carcinoma demonstrated a distinctive differential gene expression profile compared with The Cancer Genome Atlas curated conventional hepatocellular carcinomas (n = 360 cases), indicating the distinctive steatohepatitic hepatocellular carcinoma morphology is associated with a unique gene expression profile. Pathway analysis comparing tumor-nonneoplastic pairs revealed significant upregulation of the hedgehog pathway based on GLI1 overexpression and significant downregulation of carnitine palmitoyltransferase 2 transcript. Glutamine synthetase transcript was significantly upregulated, and fatty acid binding protein 1 transcript was significantly downregulated and immunohistochemically confirmed, indicating steatohepatitic hepatocellular carcinoma tumor cells display a zone 3 phenotype.ConclusionsSteatohepatitic hepatocellular carcinoma demonstrates a distinctive morphology and gene expression profile, phenotype of zone 3 hepatocytes, and activation of the hedgehog pathway and repression of carnitine palmitoyltransferase 2, which may be important in tumorigenesis.

Hepatocellular adenomas (HCAs) often pursue an innocuous clinical course. Recent work has elucidated important subtypes of HCA and biomarkers to identify them, including HCA at an increased risk for malignant transformation. Another key complication of HCAs is the risk of spontaneous tumoral hemorrhage, which may be life-threatening. Identification of a predictive biomarker for this clinical complication would therefore be of clinical value. It has been suggested that Argininosuccinate Synthase 1 (ASS1) immunohistochemistry (IHC) identifies HCA with a high propensity for hemorrhage. The aim of our study was to validate ASS1 IHC as a predictive marker of hemorrhage. Eighty-nine HCAs were collected for ASS1 IHC and subtyped according to published criteria. Clinical records were examined for evidence of tumoral hemorrhage. Twenty-one (23.6%) HCAs were complicated by clinically detected hemorrhage and were more likely to be resected (P=0.0002). Hemorrhage complicated all WHO subtypes of HCA. There was no association between hemorrhage and HCA subtype (P=0.92). Neither the distribution of ASS1 expression nor the intensity of ASS1 expression compared to normal liver showed a significant association with hemorrhage (P=0.051 and 0.34). Interlaboratory comparison of 8 cases showed good agreement regarding the intensity (6/8 and 7/8) and distribution of staining (7/8 and 7/8) across 3 laboratories performing ASS1 IHC. In conclusion, all subtypes of HCA may be complicated by hemorrhage. ASS1 IHC expression did not correlate with hemorrhagic complications. Caution is prudent before routine implementation of ASS1 IHC in clinical practice.