CD30 and CD15 highlight the HRS cells and variants with characteristic membranous and Golgi staining patterns. The characteristic HRS cells and variants typically show reactivity for EBER indicating association with EBV infection as a consequence of immunosuppression

or immunodeficiency (18). Histiocytic sarcoma (HS) This a rare neoplasm consisting of diffuse, medium to large and round to oval epithelioid cells with convoluted nuclei and abundant pale to eosinophilic, vacuolated cytoplasm. Although some cases may demonstrate monomorphous proliferation, pleomorphism is commonly encountered. Histiocytic sarcoma (HS) may morphologically mimic Inhibitors,research,lifescience,medical DLBCL or anaplastic large cell lymphoma (ALCL), and while histiocytic sarcoma usually presents as a non-cohesive infiltrate, the tumor cells may occasionally show cohesion and thus, imitate carcinoma or melanoma (19). Hence, immunohistochemistry is frequently utilized for characterization and distinction from Inhibitors,research,lifescience,medical several differential diagnoses. The histiocytic tumor cells usually express CD163, CD68 and lysozyme and lack specific lymphoid (i.e., CD3, CD20), myeloid (i.e., myeloperoxidase, Inhibitors,research,lifescience,medical CD33, CD13) or Langerhans cell (i.e., CD1a, langerin) markers (70). CD30 and epithelial membrane

antigen (EMA) are also useful in distinguishing HS from ALCL; these two markers are usually positive in ALCL (19) and negative in Inhibitors,research,lifescience,medical HS. Moreover, HS is negative for pancytokeratin, whereas carcinomas typically express this marker. Although occurrence in the GI tract is rare, HS has been documented in the stomach, colon, ileum, rectum and anus, and are often behaves in a clinically aggressive fashion (15,16,19,20). One case had widespread disease infiltration involving the liver, spleen, bone marrow and lymph nodes and showed moderate tumor pleomorphism

with multinucleated giant cells. Consequently, PD-1/PD-L1 inhibitor 2 multiple ulcerations with critical perforations were identified Inhibitors,research,lifescience,medical in the esophagus and duodenum but tumor cells were not found in these regions. It was postulated that ischemic embolism associated with the malignant process instigated mucosal damage (21). Mast cell sarcoma (MCS) Mast cell sarcoma (MCS), an exceedingly rare entity Carnitine dehydrogenase is one of the variants of systemic mastocytosis (SM). It consists of a unifocal, destructive growth of atypical mast cells in aggregates and sheets demonstrating convoluted hyperchromatic nuclei which are often bi- or multilobated, with ample amount of finely granular cytoplasm. MCS may morphologically mimic other malignancies such as histiocytic or myeloid neoplasms, as well as sarcomas with epithelioid features. Immunohistochemistry is essential in differentiating MCS from these other lesions. MCS is reactive for tryptase, CD117 and show co-expression of CD2 and CD25; the latter two highlight neoplastic mast cells (71).