Deep dermatofibrosarcoma protuberans: a pitfall in the ultrasonographic diagnosis of lipoma-like subcutaneous lesions

Dermatofibrosarcoma protuberans (DFSP) is an indolent sarcoma known for its propensity for local invasive growth and recurrence. It typically presents as a protuberant tumor mass. Rare nonprotuberant presentations have recently been described; these invariably present as pigmented or depressed plaques. Lesions arising in the subcutaneous compartment and without cutaneous manifestations have rarely been reported or emphasized in the literature. Here we report a case of deep DFSP that lacked discernible epidermal or dermal changes, was mistaken for a lipoma, and localized entirely within the subcutaneous compartment. Ultrasonography may not be useful in differentiating DFSP from benign tumors. In addition, a review of the English language literature revealed that these deep-seated tumors might be more common than originally believed. For this purpose, the current case is presented to raise awareness for DFSP, which can be present entirely in the subcutis without cutaneous manifestations and thus easily overlooked.