HISTOLOGIC AND IMMUNOPHENOTYPIC FEATURES PRIOR TO TRANSFORMATION IN PATIENTS WITH TRANSFORMED CUTANEOUS T-CELL LYMPHOMA - IS CD25 EXPRESSION IN SKIN BIOPSY SAMPLES PREDICTIVE OF LARGE-CELL TRANSFORMATION IN CUTANEOUS T-CELL LYMPHOMA

Large cell transformation (LCT) in cutaneous T-cell lymphoma (CTCL) is estimated to occur up to approximate to 20% of patients. This morphol ogic change is associated with aggressive behavior and shortened survi val. Our purpose was to identify morphologic and/or immunophenotypic f eatures in CTCL skin biopsies that are predictive of transformation We analyzed 12 cases of CTCL (three cases of mycosis fungoides and nine cases of Sezary syndrome) that underwent LCT and for which sequential biopsies before and after transformation were available. Eight of 12 c ases had pre-LCT marker studies performed on frozen tissue. The histol ogic and immunophenotypic features of CTCL and LCT were reviewed. Morp hologically, CTCL biopsies showed the following: Pautrier microabscess es (five cases), epidermotropism of single lymphoid cells (three cases ), and nonspecific histology (four cases). Immunophenotyping prior to transformation showed aberrant loss of T-cell markers (CD5, CD7, CD5 a nd CD7) in three of eight cases. CD4:CD8 ratios were increased in all cases. Expression of CD25 by the neoplastic lymphoid cells was detecte d in six of seven cases. LCT immunophenotyping showed additional loss of CD7 in one of five cases and of CD25 in three of five cases. In con clusion, expression of CD25 in CTCL may identify a subset of patients at risk of undergoing LCT.