The value of immunohistological techniques in undifferentiated cancers.

From 1980 to 1984, we observed 144 undifferentiated cancers, of which 116 (0.9% of all cancers treated during this period) were treated in our center. Immunohistochemical study classified 130 tumors (90%), which comprised 82 non-Hodgkin's lymphomas (57%), 32 carcinomas (22%), 7 melanomas (5%), 7 sarcomas (5%) and 2 others (1%). Sixty-nine patients, with the diagnostic problem of non-Hodgkin's lymphoma versus carcinoma, which was solved by immunohistology, were followed up for 44 +/- 20 months. Lymphomas (57 cases) had a better clinical course than carcinomas (11 cases), and a clinical course similar to high-grade lymphomas identified by conventional histology. For 66 patients with the same problem, the treatment was started before the immunohistochemical diagnosis. This treatment was inappropriate in the light of the correct diagnosis in 16 of 66 cases (24% of all cases).