Eyelid Signet Ring Cell/Histiocytoid Carcinoma

**Semantic type:** Neoplastic Process

**Definition:** A rare aggressive adnexal carcinoma that arises from the eyelid. It often affects both the upper and lower eyelids and manifests with painless swelling, usually in elderly males. Morphologically, it is characterized by the presence of signet ring cells or histiocytoid epithelial cells with eosinophilic cytoplasm infiltrating the dermis and subcutis, often in a single file pattern.

**Synonyms:** - Eyelid Signet-Ring Cell/Histiocytoid Carcinoma