The clinical and histopathologic features of specific skin infiltrates in patients with B-cell chronic lymphocytic leukemia (B-CLL) have rarely been reported in detail. In this study we analyzed the clinical, histopathologic, immunophenotypic, and molecular features of 84 skin lesions from 42 patients (M:F = 1.3:1; mean age, 66.0 years; range, 42-83 years) with specific cutaneous manifestations of B-CLL. The duration of B-CLL before skin manifestations varied from 0 to 142 months (mean, 39 months). In seven patients (16.7%), skin lesions represented the first sign of disease. Clinical presentations included localized or generalized erythematous papules, plaques, nodules, and large tumors. Ulceration was uncommon. In six patients lesions were confined at the sites of scars from previous herpes zoster (four patients) or herpes simplex (two patients) eruptions. Histologically, three main patterns were recognized: (a) patchy perivascular and periadnexal, (b) nodular-diffuse, and (c) bandlike. Cytomorphologically, small monomorphous lymphocytes predominated. Proliferation centers were observed in only four specimens. In two patients presenting with tumors, a high content of large cells with features of centroblasts and immunoblasts was found (Richter's syndrome). Immunohistologic analyses were performed on paraffin-embedded specimens in 40 biopsies from 20 patients and on cryostat sections in 17 biopsies from 11 patients. Neoplastic B lymphocytes in all cases showed an aberrant phenotype (paraffin sections: CD20+ /CD5+/ CD43+; cryostat sections: CD19+ /CD5+; immunoglobulin light-chain restriction). Proliferation markers (Ki67, PCNA, MIB1) stained 5 to 80% of cells (mean, 25%; median, 20%). Polymerase chain reaction performed in nine cases on paraffin-embedded tissues using consensus primers for immunoglobulin heavy-chain genes showed a monoclonal population of B lymphocytes in all cases. Several discrete bands in addition to the prominent ones were noted in five cases, indicating the additional presence of B lymphocytes whose immunoglobulin genes were not monoclonally but oligoclonally rearranged. Follow-up data could be obtained from 31 patients. The two patients with Richter's syndrome died after 5 and 8 months, respectively. The 5-year survival of patients with small-cell cutaneous B-CLL was 66.6%. Our study indicates that cutaneous specific manifestations of B-CLL present with characteristic histologic, immunophenotypic, and molecular patterns. Prognosis in these patients is probably not affected by skin involvement.