Subcutaneous lymphoma and related conditions.

A variety of lymphoma entities can involve the subcutaneous tissue. The term subcutaneous panniculitis-like T cell lymphoma is now solely utilized for primary cutaneous CD8+ lymphomas expressing the alphabeta T cell receptor heterodimer. This condition is generally responsive to treatment; however, the development of the hemophagocytic syndrome is a poor prognostic indicator. Overlapping features with lupus panniculitis has been observed, and cases with ambiguous pathology may be classified as atypical lobular lymphocytic panniculitis. These ambiguous cases often respond to systemic steroids or methotrexate. Overall, this condition follows an indolent course; however, evolution into frank lymphomas in some cases reflects the diagnostic difficulties of these conditions. Gamma-delta lymphomas have a poor prognosis regardless of the presence or absence of a hemophagocytic syndrome. Treatment options are limited because of lack of large studies and the rarity of this condition. Prolonged remission may be achieved with allogeneic stem cell transplantation.