A Rare Case of High grade Epithelioid Malignant Neoplasm with CAM 5.2 Expression and (EML4–ALK) Fusion in a Pediatric Patient

Abstract

Abstract Introduction/Objective ALK (anaplastic lymphoma kinase) fusions have been identified in lymphomas and diverse cancer types including carcinomas, melanomas and mesenchymal neoplasms such as inflammatory myofibroblastic tumors (IMT), epithelioid fibrous histiocytoma (EFH). Herein we present a (non IMT, non EFH) ALK rearranged aggressive epithelioid neoplasm. Methods/Case Report We report a 17-year-old male with a 14.0 cm mediastinal mass and extensive metastatic disease involving brain, bones, pleura and lymph nodes. The tumor was made of epithelioid like cell with round nuclei, prominent nucleoli and a moderate amount of cytoplasm, arranged in a nested pattern. Ki-67 showed a high proliferative index, >70%. The tumor cells were positive for CAM 5.2; weakly positive for AE1/3, ALK, CD30; focally positive for p63, p53, S100. Additional stains including CD117, PLAP, OCT-4, Sall-4, glypican-3, synaptophysin, chromogranin, CK5/6, p40, pan-melanoma, myogenin, CD99, WT1, CD34, CD45, CD138, MUM1, CD2, CD4, CD5, CD3, CD7, CD15, CD23, CD31, CD20, CD79a, CD15, PAX8, PAX5, CD43, MPO, desmin, D2-40, Calretinin, ERG, SOX-10, PD-L1 and NUT-1 were all negative. Both BRG and INI1 were retained. The keratin positivity and the lack of “hallmark” cells made anaplastic large cell lymphoma (ALCL) less likely. The absence of desmin and CD30 excluded the rare epithelioid IMT sarcoma. Next-generation sequencing detected an (EML4–ALK) fusion. A diagnosis of high- grade epithelioid malignant neoplasm with (EML4–ALK) fusion was made. Most cases of this category were described as low grade-appearing spindled cells within a myxoid stroma arranged in fascicles (+S100, +CD34) and have unaggressive behavior. Only three cases, were characterized by epithelioid high- grade morphology and metastatic nature. They shared features like little collagenous stroma, conspicuous mitotic activity and tumor necrosis. Results (if a Case Study enter NA) NA Conclusion Identification of kinase fusions was essential for precise classification, better knowledge of this epithelioid high grade malignant neoplasm and for targeted therapy purposes. The significant clinicopathologic heterogeneity of this emerging group requires further investigation.