Abstract

Pseudocarcinomatous hyperplasia (PCH) is a reactive proliferation of the epithelium associated with a variety of inflammatory and neoplastic conditions including CD30+ lymphoproliferative disorders. Distinguishing PCH from other entities such as squamous cell carcinoma (SCC) can be a diagnostic challenge as PCH can resemble SCC both clinically and histologically. Herein we present a case of a 42-year-old Caucasian male with a solitary, enlarging right thigh mass. He reported a 10-year history of faint erythema that progressed to an ulcerating mass with 3 months of subjective fever, fatigue, and chills. Physical exam revealed a 6.5 x 6.0 cm, ulcerated, crusted plaque with surrounding erythema on the right upper thigh. A punch biopsy revealed a lichenoid dermatitis with an atypical CD30+ infiltrate. The patient underwent excision that demonstrated a CD30+ population (ALK-1 negative) and a marked concomitant pseudocarcinomatous hyperplasia akin to a well-differentiated SCC. Sentinel lymph node and bone marrow biopsies were negative. The final diagnosis was that of CD-30+ primary cutaneous anaplastic large cell lymphoma (PC-ALCL) with reactive pseudocarcinomatous hyperplasia. Previous cases and literature reviews have demonstrated that PCH can occur with ALCL, ranging from mimicking poorly differentiated to well differentiated SCCs. Here we present a case of the reactive pattern resembling well-differentiated SCC in C-ALCL to add to the growing literature. The significant overlap both clinically and histologically should compel dermatopathologists to consider additional testing to avoid erroneous diagnosis especially when lesions are found in atypical sites for SCC, or in younger patients in non-sun-exposed areas.

Financial Disclosure:
No current or relevant financial relationships exist.