The Value of Clonality in the Diagnosis and Follow-up of Patients With Cutaneous T-cell InfiltratesDadej, Katarzyna; Gaboury, Louis M.D., Ph.D.; Lamarre, Louis M.D.; Pétorin, Caroline M.D.; Séguin, Chantal M.D.; Cadotte, Marcel M.D., M.Sc.; Gòrska–Flipot, Isabelle Ph.D.Author Information From the Laboratory of Oncopathology (K.D., L.G., C.P., I.G.-F.), Department of Pathology (L.G., L.L., M.C.) and Dermatology. Division of Department of Medicine (C.S.), Centre hospitalier de l'Université de Montréal; and the Department of Pathology (L.G.), Université de Montréal, Québec, Canada. Supported by departmental funds and by a grant from Lafond et Associés. Address correspondence to Dr. Isabelle Gòrska–Flipot, Laboratory of Molecular Oncopathology, Department of Pathology, Hôtel–Dieu du Centre hospitalier de l'Université de Montréal, 3840 rue St-Urbain, Montréal, Québec, Canada H2W 1T8 (e-mail: [email protected] ssss.gouv.qc.ca). Diagnostic Molecular Pathology: June 2001 - Volume 10 - Issue 2 - pp 78-88 Buy Abstract The diagnosis of early stages of cutaneous T-cell lymphoma (CTCL) is often difficult, especially for lesions that are at the borderline between reactive and neoplastic skin T-cell infiltrates. T-cell monoclonality in these lesions is considered by some to be an important prognostic factor of neoplastic evolution, whereas others claim that clonality can also be found in benign skin infiltrates and is therefore of limited diagnostic value. To address this controversy, the authors analyzed retrospectively eight patients with lymphocytic skin lesions who progressed to CTCL, and three patients with recurrent T-cell lymphocytic infiltrates who had not developed CTCL. From a total of 65 biopsies of eight progressing patients, 32 were diagnosed as histologically malignant and 33 were diagnosed as benign or borderline. The authors found clonality by either polymerase chain reaction or Southern blot analysis in 88% of malignant and in 79% of nonmalignant lesions. None of the 37 biopsies of nonprogressing patients was clonal. These results indicate strongly that the presence of monoclonality in T-cell skin infiltrates is related closely to the risk of developing CTCL. The value of clonality as a marker of malignancy is supported by the absence of T-cell clonal populations in all infiltrates from patients who had not progressed to lymphoma. © 2001 Lippincott Williams & Wilkins, Inc.