Transformation of cutaneous T cell lymphoma to large cell lymphoma. A clinicopathologic and immunologic study.

Some patients with cutaneous T cell lymphoma (CTCL) develop a high-grade, large-cell lymphoma associated with rapid deterioration of clinical status. This change in histologic appearance and clinical behavior of CTCL is similar to transformations of other hematopoietic and lymphoid neoplasms. From a group of 92 cases of CTCL, morphologic, immunologic and clinical features were studied in 17 cases of transformed CTCL. Transformation was noted, at presentation or subsequently, in either cutaneous or extracutaneous sites; remarkably, transformation was found at initial diagnosis of CTCL in 7 of 17 patients. T cell characteristics were maintained in all 17 cases of transformed CTCL; in 11 cases with complete phenotypes, there were 6 T-helper, 3 T-suppressor, and 2 aberrant T subtypes. The pre- and posttransformation phenotypes were similar in 3 of 7 cases tested over time (all T-helper); retention of T-suppressor phenotype was suggested in another case. T cell features were maintained in the other 3 cases, but the T subtypes were altered in 2 of these cases. Absent or diminished pan-T antigens (CD 5, CD 3, or UCHL1) were found in 9 of 17 cases. Leu-M1, Ki-1, or LN 2 antigens were expressed by transformed cells in 10 of 17 cases, often in patterns identical to Reed-Sternberg cells. Survival in patients with transformed CTCL was significantly shorter (median, 29 months) than in 44 CTCL patients without transformation (58 months, P = 0.015); survival after diagnosis of transformation was short (12 months). Patients with extracutaneous transformation had a shorter median survival after transformation (8 months) than those with transformation limited to skin (19 months). It is concluded that CTCL can transform morphologically to a large cell variant associated with aggressive behavior and shortened survival. Extracutaneous transformation apparently indicates a poorer prognosis than cutaneous transformation. Although transformed CTCL usually retains a T cell phenotype, some antigens are lost while other new antigens may be expressed. Recognition of transformed CTCL is facilitated by identification of the dysplastic cerebriform cell component, but often requires correlation of immunologic and clinical features.