[Carcinoma of unknown origin. Diagnostic study of 48 cases and its clinical yield].

Forty-eight patients fulfilling the criteria for carcinoma of unknown origin (CUO) between April 1983 and December 1987 were retrospectively analyzed. Mean age was 62 (33-83). Twenty-seven were males (56%) and 21 females (44%). The most common site of metastasis was the bone (35%), followed by the liver (19%) and lymph nodes (19%). 58% of cases were adenocarcinomas. Overall 274 studies for the detection of the primary tumor were carried out, the diagnosis being achieved in 10 cases (3.65%) which corresponded to lung neoplasms (5 cases), prostatic adenocarcinoma with negative markers (2 cases), bile duct neoplasms (2 cases) and pancreatic carcinoma (1 case). In our series, the most useful studies were computed tomography (CT) and fibrobronchoscopy. The necropsy, carried out in 11 patients, yielded 8 additional diagnoses: pulmonary neoplasm (one case), gastric adenocarcinoma (2 cases), malignant melanoma (2 cases), small intestine neoplasm (one case), parotid cancer (one case) and hepatocarcinoma (one case). Thirty-five patients were treated with chemotherapy and/or radiation; 12 objective responses (3 complete and 9 partial) were achieved, with a median duration of the response of 10 months (range 0.2-78 +). In view of the low diagnostic yield of the studies in patients with CUO we feel that the diagnostic study may be limited to CT scan with evaluation of the possible usefulness of bronchoscopy in individual patients. Regarding therapy, it is to be noted that there was a tendency for a longer survival in patients who responded.