Immunologic aspects of unknown primary melanoma.

Immune responses of 36 patients with stage II unknown primary melanoma were compared to those of 83 stage II patients with known primary melanoma. The two groups of patients were similar in age, sex, and extent of disease. Delayed cutaneous hypersensitivity to dinitrochlorobenzene (DNCB) was nearly identical in both groups. Patients with unknown primary melanoma had a mean level of reactivity of 4.7 +/- 0.37 and the patients with known primary had a mean level of 5.0 +/- 0.17. Of unknown primary patients 4.2% were unreactive to DNCB and 4.8% of known primary patients were unreactive. Antibodies to cultured melanoma cells were slightly more prevalent in serum from the unknown primary patients (67%) than from known primary patients (45%), but mean titer of positive sera did not differ significantly. Lymphoproliferative assays did not demonstrate differences in lymphocyte reactivity among the two groups when tested with Concanavalin A, mixed leukocyte culture, or unstimulated lymphocyte blastogenesis. No differences could be detected in these assays of humoral and cellular immune responses when patients with unknown primary melanoma were compared to those with known primary melanoma and similar clinical characteristics.