Periocular Histiocytoid Carcinoma: Potential Diagnostic Challenges.

Cutaneous histiocytoid carcinoma can occur as a primary tumor of the periocular region. Morphologically similar histiocytoid carcinomas arising as primary tumors of the breast have a predilection for orbital metastases. They can occasionally contain regions with prominent vacuolated cytoplasm and minimal nuclear atypia, which mimic benign histiocytic lesions. Differentiating nonneoplastic, primary neoplastic, and metastatic histiocytoid lesions involving the periorbita can be challenging for both the clinician and the pathologist, and this distinction has management implications. Herein, we present 3 cases to illustrate the challenges of diagnosing periocular histiocytoid carcinoma.