Medline: 8503025

Seminars in Oncology 20(3): 287-291, 1993.

Poorly differentiated neuroendocrine carcinoma of unknown primary tumor site.

Garrow GC, Greco FA, Hainsworth JD


Neuroendocrine tumors were originally grouped together on the basis of the presence of a dense core of neurosecretory granules and production of particular peptides. However, this grouping is not a useful indicator of their biology, and is of little or no practical clinical use for a tumor of unknown site. The three main groups of neuroendocrine tumors of unknown primary site are: metastatic carcinoid tumors whose behavior and treatment is identical to those with defined primaries; small-cell carcinomas which are aggressive tumors whose origin is most commonly the lung, and which generally should be treated similarly to small-cell lung carcinomas; and what are defined by light microscopy as 'poorly differentiated carcinomas or neoplasms' whose diagnosis as neuroendocrine tumors (some 10% of the total) can only be definitively established by electron microscopy. Data are summarized for 29 patients in whom the retroperitoneum, lymph nodes and mediastinum were the most frequently involved, with 17 of them having metastatic disease at two or more sites, and none showing evidence of hormone-related syndromes. Diagnosis was established in 24 by dense core granules seen on electron microscopy, in 4 by light microscopy (as small-cell anaplastic carcinoma), and in 1 by staining indicative of neuroendocrine origin (neuron-specific enolase, serotonin and chromogranin). Specific diagnoses made subsequently in the course or on autopsy in 4 patients included 2 undifferentiated carcinoids (only 1 primary found in the rectum), 1 small-cell lung cancer, and 1 extragonadal germ cell tumor with neuroendocrine differentiation. Cisplatin-based chemotherapy (with etoposide, or with vinblastine and bleomycin, or with bleomycin and etoposide) or regimens used to treat small-cell lung carcinoma (CAV with or without etoposide), produced 6 complete and 12 partial responses. Three patients were free of disease more than 2 years after therapy; response duration in partial responders was 6 months. Three patients with localized adenopathy underwent surgical excision and 1 with a single site of bone involvement had radiotherapy; none of these had chemotherapy and all are long-term disease-free survivors. The response rate to chemotherapy of 78% is similar to results in the literature of 82% (van der Gaast et al, Cancer; 65:422, 1990) and 67% (Moertel et al, Cancer; 68:227, 1991). Responsiveness of these tumors to therapy necessitates early, accurate diagnosis and treatment. A chromosome abnormality has been identified (11;22 translocation) for a single class of these tumors, peripheral neuroepitheliomas. (16 Refs.)

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