Mycosis fungoides (MF) is the most common of the family of cutaneous T-cell lymphomas, accounting for 65% of all cases of cutaneous T-cell lymphomas. The classic phenotypic profile is one defined by CD4+ T cells showing a reduction in the expression of CD7 and CD62L. There are 3 previous reports describing CD20 expression in MF. The cell surface antigen CD20 is a transmembrane glycosylated phosphoprotein expressed in the early stages of B-cell development before differentiation into plasma cells. Two male patients, aged 14 and 44 years, presented with persistent truncal plaques up to 8 cm of 1 and 4 years duration, respectively. A third patient, an 80-year-old female, presented with a 1-year history of progressive nodules involving the head and neck area. Cases 1 and 2 both responded to topical treatment modalities. The biopsies in cases 1 and 2 showed features typical of plaque stage MF, whereas case 3 was compatible with follicular MF with tumor stage transformation. Phenotypically, the aberrant cell populace demonstrated a CD4+, CD7−, and CD62L− phenotype; at variance with classic MF was the expression of CD20. Although there were a few PAX5-positive staining cells, definitive colocalization studies were negative. Other B-cell markers and heavy chain immunoglobulin rearrangement were not detected. There are a growing number of reports describing T-cell lymphomas and leukemias with CD20 expression. Of the 6 CD20+ MF cases reported in the literature to date, 3 have been associated with a more aggressive clinical course; all but one case have occurred in males.
*Department of Medical Education, Weill Medical College of Cornell University, New York, NY
†Departments of Dermatology and Dermatopathology University of Connecticut Dermatology Associates, University of Connecticut Health Center, Farmington, CT
‡Department of Pathology and Laboratory Medicine, Weill Medical College of Cornell University, New York, NY.
Reprints: Cynthia M. Magro, MD, Department of Pathology and Laboratory Medicine, Weill Medical College of Cornell University, Box 58, Room F-309, 1300 York Avenue, New York, NY 10065 (e-mail: firstname.lastname@example.org).
The authors declare no conflicts of interest.