Folliculosebaceous Cystic Hamartoma With Prominent Adipose Tissue Resembling Spindle Cell Lipoma

Folliculosebaceous cystic hamartomas (FSCH) are a rare form of cutaneous hamartoma composed of follicular, sebaceous, and mesenchymal elements. These lesions are most often seen in the central face and scalp and rarely exceed 2 cm in size. Here, we report a case of a folliculosebaceous cystic hamartoma with a prominent adipose tissue component resembling a spindle cell lipoma. The patient is a 36-year-old man with a slowly enlarging, flesh-colored, lobulated lesion on his right ala that had been previously biopsied. The clinical differential included a hypertrophic scar or recurrent hamartoma. A full-thickness excisional biopsy was performed, which revealed prominent, large, irregularly shaped, folliculosebaceous structures, including multiple dilated follicles associated with prominent hyperplastic-appearing sebaceous glands, findings consistent with FSCH. The mesenchymal component contained a proliferation of spindle-shaped cells associated with mucin and thickened, ropey-appearing bundles of collagen, features mimicking a spindle cell lipoma. This combination of a folliculosebaceous cystic hamartoma with prominent adipose tissue resembling spindle cell lipoma is unusual and has only been previously reported once in the literature, and therefore, our case contributes to the expanding knowledge of this rare variant of FSCH.