Composite lymphoma of mycosis fungoides and cutaneous small B-cell lymphoma in a 73-year-old male patient.

Composite lymphoma of T-cell and B-cell type is uncommon, and the one occurring primarily on skin is extremely rare. Herein, we report a unique case of composite lymphoma of mycosis fungoides and cutaneous small B-cell lymphoma in a 73-year-old male patient. The patient presented with multiple erythematous patches, plaques, and nodules on the upper arms, scalp, and trunk. Four punch biopsies of arm and scalp lesions demonstrated lymphoid infiltrate in superficial to deep dermis with a characteristic zone distribution of T-cell and B-cell components. T cells were distributed in papillary and perifollicular dermis and displayed a larger size with convoluted nuclei, whereas B cells were small sized, assuming nodular infiltrate in mid-deep dermis with coexpression of CD5. Molecular test detected clonal rearrangement of both TCRG and IGH/K genes with identical amplicons for each gene in all 4 biopsies. Clinical staging revealed no extracutaneous lesions. A multidisplinary approach is emphasized to establish a definitive diagnosis.