We describe five cases of mantle cell lymphoma involving skin. Three patients initially presented with skin lesions but had evidence of widespread disease at time of diagnosis or with relatively short follow-up. One patient was known to have disseminated disease before he developed skin lesions. One patient presented with a solitary skin nodule on the thigh and has developed multiple smaller nodules on the same leg, but no other sites of disease over 30 months of clinical follow-up. This case fulfills the criteria for primary cutaneous lymphoma as proposed by the European Organization for Research and Treatment of Cancer. Biopsy of the skin lesions in all cases showed predominantly dermal and focally subcutaneous lymphoid infiltrates, preferentially perivascular and periadnexal in four cases, and nodular in one case. The tumors were composed of small- to medium-sized lymphocytes with irregular nuclear contours. Four cases had blastoid and one case had typical cytologic features. Immunophenotypic studies showed that all cases were positive for CD20 and cyclin D1, and four of five were positive for CD5. Four cases, including the CD5-negative case, had evidence of the t(11;14) shown by either fluorescence in situ hybridization methods performed on skin tumors or conventional cytogenetic analysis performed on involved bone marrow. We conclude that mantle cell lymphoma can involve skin, usually as a manifestation of disseminated disease, and is often associated with blastoid cytologic features. Rare cases of mantle cell lymphoma may arise in skin.