Abstract
Histiocytic Sarcoma is a rare malignant hematopoietic neoplasm that can present in extranodal sites including lymph nodes, skin, gastrointestinal tract, and the central nervous system. Only 10% of cases manifest as skin lesions and very few are reported in the head and neck. The authors report a case of histiocytic sarcoma of the eyelid in a 72-year-old male that was clinically diagnosed as a chalazion. Initial excision was not sent for routine histopathological assessment and the patient was subsequently lost to follow up. Recurrence occurred at the eyelid site and additional lesions were found on the forearms, abdomen, and right knee. Histopathological assessment of one of these other sites confirmed the diagnosis of histiocytic sarcoma. To our knowledge, this is the first reported case of disseminated histiocytic sarcoma that originally presented in the ocular adnexa (eyelid). And, as the initial lesion was not sent to Pathology and therefore potentially missed, this case highlights the importance of submitting tissue, including chalazia, for pathologic evaluation.