Metastatic cancer with unknown primary

Close cooperation between an experienced pathologist and oncologist is essential in the management of patients with unknown primary carcinoma. A comprehensive pathological examination is crucial and, with undifferentiated tumors, this will include immunohistology and/or electron microscopy. Ample properly processed tissue therefore must be provided. Time-consuming and costly radiographic and imaging studies should be avoided. No matter how extensive the evaluation, in a majority of cases, the primary site will never be found, so a selective search for treatable tumors is most appropriate and cost-effective. With adenocarcinomas, this will include prostate, breast, and ovary; for undifferentiated tumors, small cell bronchogenic carcinoma, lymphomas, and germ cell tumors. Table 4 summarizes recommended studies for diagnosing unknown primary undifferentiated or adenocarcinomas. Women with adenocarcinoma in axillary nodes without a primary site should be treated as having breast cancer. Estrogen and progesterone receptor assays are to be obtained on the axillary biopsy. High and midcervical nodes with metastatic squamous cell carcinoma can be treated effectively and, not infrequently, cured with surgery and radiation therapy, even if the primary site never is detected. If doubt remains, treatment should be selected that offers the best chance of significant palliation or cure--for example, cisplatin-based chemotherapy in possible extragonadal germ cell tumors.