There is an increased risk of malignancy in patients with genetically determined or acquired immunosuppression. The authors report a case of a 70-year-old patient with a lymphoplasmocytic immunocytoma who developed 19 squamous-cell carcinomas (SCC) and nine basal-cell carcinomas (BCC) over a three-year period. This was the reason to review 100 cases of malignant lymphomas for evidence of additional malignancies. Of these patients, 15% had one or more SCC or BCC in the head and neck area. The age range was 59 to 79 years (mean, 71.7 years) and the male:female ratio 11:4. One or more SCC arose in 93% of these patients, 36% developed an additional one or more BCC, and BCC alone occurred in 7%. The usual ratio of BCC:SCC is 10:1; in the authors' patients, by contrast, this ratio was 6:14. In 12 cases, SCC and BCC were located on the skin. The remaining cases of SCC developed in the oral mucosa, the tonsils and the hypopharynx. In 13 cases, low-grade malignant lymphomas were found and in two cases high-grade malignant lymphomas were found. The SCC were clinically aggressive. Thirty-six percent of the patients had recurrent lesions, 43% multiple neoplasms, and 50% metastases. Histologically, the SCC showed moderate to poor differentiation, a high degree of cell polymorphism and mitotic activity, and deep tissue infiltration. There are several explanations for the increased incidence of neoplasms in patients with immunodeficiency disorders. The surveillance function of the immune system may be impaired due to the disease itself or due to the treatment for immunosuppression. Immunosuppressive and cytotoxic agents are potential carcinogens.(ABSTRACT TRUNCATED AT 250 WORDS)