Answer: Pleomorphic lipoma

Histology: The lesion is relatively circumscribed. It is largely comprised of multinucleated giant cells dispersed in a background of mature fat and collagen bundles. The nuclei of the giant cells are hyperchromatic, pleomorphic, and arranged peripherally arranged. Mitotic figures are not observed.

Discussion: Pleomorphic lipoma is a benign lipomatous tumor that is regarded as a pleomorphic variant of spindle cell lipoma. Most lesions present as a solitary, painless, slow-growing nodule of the dermis or subcutis of the shoulders or posterior neck regions. Atypical lipomas are not common. Owing to their astonishing pleomorphism, they may easily be mistaken as a pleomorphic liposarcoma or some other pleomorphic sarcoma by the unwary pathologist unfamiliar with its peculiar histology. Important features distinguishing pleomorphic lipoma from its malignant counterpart are it relative circumscription and its superficial location. While mitotic figures may be observed, they are not abundant.