Torres‐Mora, Jorge

Epithelioid hemangioendothelioma (EHE) is an uncommon low-grade malignant vascular tumor that may arise in soft tissue/bone or visceral sites such as the liver and lung. As this tumor exhibits epithelioid morphology, it frequently causes diagnostic confusion with other epithelioid vascular neoplasms as well as carcinoma. While 90% of classic EHE are driven by aWWTR1-CAMTA1fusion gene, a histologically distinctive subset of EHE has been recently shown to harbor a different fusion gene,YAP1-TFE3. This variant is likely underrecognized given its rarity and only recent description. Notably, EHE frequently involves the liver but only one case of hepaticYAP1-TFE3rearranged EHE has been reported to date. We present the second case ofYAP1-TFE3rearranged EHE affecting a 65-year-old woman and presenting as multiple liver masses, with characterization of the fusion gene at the transcriptomic and genomic levels. There are several educational points noted from this case.YAP1-TFE3rearranged EHE shows distinctly vasoformative foci, unlike classic EHE and mimicking angiosarcoma or epithelioid hemangioma. The tumors cells show a histiocytoid appearance with voluminous cytoplasm, similar to otherTFE3-rearranged tumors. Finally, in the liver, this tumor may in part mimic focal nodular hyperplasia of the liver which is an underrecognized diagnostic pitfall. This report highlights the key diagnostic and genetic features of this newly recognized variant of hepatic EHE to aid pathologists in appropriately classifying these tumors.

Abstract OBJECTIVES Paragangliomas have unique features in the mediastinum, in part due to their location. Because of their paucity, they have not been thoroughly investigated. We studied the clinical, pathological, immunohistochemical and molecular features of mediastinal paragangliomas. METHODS Immunohistochemistry, next-generation sequencing mutation panel and the Oncoscan assay were performed. RESULTS Twenty-four patients with mediastinal paraganglioma (7 men, 29.2%) had a median age of 45.5 years (19.8–72.2). Twenty-one (87.5%) paragangliomas were completely resected. Six (of 24, 25.0%) tumours were considered metastatic. Mitotic activity occurred in 11 (of 24, 45.8%) paragangliomas. Programmed death-ligand 1 (PD-L1) (n = 23) was expressed in 6 (26%) patients in 10% (n = 2) and 1% (n = 4) of tumour cells, respectively. SDHB expression was lost in 19 (of 22, 86.4%) cases. ATRX expression was lost in 11 (of 23, 47.8%) cases. Next-generation sequencing revealed a single pathogenic mutation in 10 (of 19) specimens including SDHB (n = 4), SDHD (n = 6), SDHC (n = 1), ATRX (n = 1), and ≥2 mutations in 2 cases [SDHC and TERT (n = 1); SDHB, ATRX and TP53 (n = 1)]. Germline mutation analysis revealed the same succinate dehydrogenase mutation (or lack thereof) as identified in the paraganglioma in 11 (of 12) cases. During a median follow-up (n = 21) of 4.8 years (0.8–14.9), 3 patients developed metastases; 4 patients died, at least 1 of disease. CONCLUSIONS Mediastinal paragangliomas can be associated with morbidity and mortality. Many mediastinal paragangliomas have been reported to be associated with syndromes such as multiple endocrine neoplasia, von Hippel-Lindau or succinate dehydrogenase syndrome with mutation profiles dominated by alterations in genes associated with these syndromes.

Acellular dermal matrix (ADM) such as Alloderm®is sometimes used in tissue reconstruction in primary and reconstructive breast surgeries. As ADM is incorporated into the native tissues, the evolving imaging findings that would correlate with varying degrees of host migration and neoangiogenesis into the matrix can be challenging to recognize. In the setting of a palpable or clinical area of concern after breast reconstructive surgery following breast cancer, confident diagnosis of a mass representing ADM rather than recurring or developing disease can be challenging. Such diagnostic imaging uncertainties generally result in short-term imaging and clinical follow-up, but occasionally, biopsy is performed for histopathological confirmation of benignity. A case of biopsy-proven Alloderm®is described. To the best of our knowledge, this is the first radiologic-pathologic correlation of ADM in the literature.

Liposarcoma is one of the most common sarcomas in adults, but only rarely presents as an esophageal primary. There have been several reports of well-differentiated liposarcoma (WDL) arising in the esophagus, but we present a case of dedifferentiated liposarcoma (DL) presenting as a large esophageal polyp. We believe this is the first reported case of DL of the esophagus with morphologic evidence of both well-differentiated and dedifferentiated components. The diagnosis was confirmed by demonstration of CPM gene amplification by fluorescence in situ hybridization (FISH).