A Rare Malignancy of the Eyelid: Report A Case of Primary Periocular Histiocytoid Carcinoma.

Primary periocular histiocytoid carcinoma is a very rare malignant tumor. Until now, less than 50 cases have been reported in the English literature. It is characterized by resistant epiphora, limitation in extraocular motility, and ptosis. The definitive diagnosis of this lesion is made based on detecting histological histiocytoid features along with tracing positivity of specific biomarkers using immunohistochemistry. However, pathologists may be faced with two major obstacles in the diagnosis of this tumor including distinguishing it from metastatic histiocytoid lesions and also from benign mimics such as reactive inflammatory lesions. Here, we describe a case of primary periocular histiocytoid carcinoma located on the eyelid as well as review the literature to clarify the histopathological and diagnostic features of this tumor.