Pyoderma gangrenosum or cutaneous lymphoma: a difficult clinical diagnosis.

Pyoderma gangrenosum is frequently associated with an underlying condition such as ulcerative colitis or a myeloproliferative syndrome. However, lymphoproliferative malignancies have only rarely been seen concurrently with pyoderma gangrenosum. We present the case of a patient with small lymphocytic lymphoma who noted a slowly enlarging skin ulcer that was clinically consistent with pyoderma gangrenosum. Examination of a biopsy specimen showed infiltration of the skin with lymphoma cells as well as deeper necrotic material and thrombosis of vessels that were infiltrated by lymphoma. This case illustrates the difficulty of differentiating pyoderma gangrenosum from cutaneous lymphoma clinically.