Primary cutaneous B-cell lymphoma, leg type restricted to the subcutaneous fat arising in a patient with dermatomyositis.

Until now, cutaneous lymphoma limited to the subcutaneous fat has been described as being derived only from T cells. Subcutaneous panniculitis-like T-cell lymphoma has been reported as a rare, postthymic neoplasm with various associations, including dermatomyositis. Furthermore, primary cutaneous B-cell lymphoma of the leg is defined by a diffuse dermal infiltrate of neoplastic B cells with extension to both the papillary dermis and the subcutaneous fat. We report a case of a patient with dermatomyositis who developed a cutaneous lymphoma of B-cell origin restricted to the subcutis, the first of its kind reported in the literature. This malignancy spared the dermis and epidermis, and we suggest that this is a unique variant of primary cutaneous B-cell lymphoma of the leg.