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Case Reports

Abstract

Extremely rare instances of carcinosarcoma (CS) arising from preexisting eccrine spiradenoma (ES) have been reported. These cases are characterized by both epithelial and mesenchymal components. Here, we present one such case and discuss the histopathological features and diagnostic challenges of this rare malignancy. A 61-year-old female presented with a recently progressively enlarging, painless, left thigh mass of 4-year duration. MRI revealed a 6.3 cm, hyperintense, heterogeneous mass within the subcutaneous tissue raising concerns for soft tissue sarcoma. The initial biopsy report was suggestive of an eccrine spiradenoma. Given the large size of the tumor, a complete excision was performed. Grossly, a well-delineated, multicystic mass, with focal degeneration (calcification and hemorrhage) was received. Microscopically, the tumor showed an architecture of ES with a transition into a carcinoma characterized by sheets of pleomorphic epithelioid cells forming focal glands, and further transition into a sarcoma, characterized by striking cytologic atypia, nuclear pleomorphism, brisk mitosis, and tumor necrosis. Areas of squamous differentiation with clear cell change, and heterologous chondro-, osteo-, and rhabdosarcomatous changes were seen. Immunostains in the sarcoma revealed positive SMA with loss of AE1/AE3, CK5/6, P40, and P63. P53 overexpression was seen in this area with loss of MYB staining. Due to its rarity and complex histology, this can be challenging to diagnose and manage. There is a significant potential for local recurrence, distant metastasis, and disease-related mortality. Because it can be related to a genetic syndrome, a complete evaluation of patients and consideration for assessment by medical genetics is recommended.