Primary thymic carcinomas.

Within a 75-year period, 20 patients with primary nonteratomatous carcinomas of the thymus were seen at the Mayo Clinic. Fourteen were males and six were females, with a mean age of 48 years. Thirteen of the lesions were classified as poorly differentiated or spindling squamous cell carcinomas. One neoplasm was a sarcomatoid carcinoma, and two showed both squamous cell and neuroendocrine ultrastructural features. The remaining four tumors had both light- and electron-microscopic features of neuroendocrine carcinomas. In all 20 patients, careful clinical and pathologic examinations, including autopsy in fatal cases, excluded malignant lymphomas and metastasis to the thymus from epithelial tumors in other anatomic sites. Thirteen patients underwent surgery, with or without postoperative radiotherapy; of these, one was alive and apparently disease-free 43 months after diagnosis. There were two operative deaths. The remaining patients received primary radiotherapy or chemotherapy, or both. The mean survival of the 16 patients who died (excluding operative deaths) was 18.7 months for the 14 patients with tumors of squamous cell differentiation and 36.0 months for the two patients with pure neuroendocrine carcinomas. Among patients with squamous cell carcinoma, 11 developed metastases to lungs, liver, bones, adrenal glands, or extrathoracic lymph nodes; nine of these died of massive local growth within the mediastinum. Among patients with neuroendocrine carcinomas, two of four patients died of local growth within the mediastinum; one of these also had metastases to the liver and adrenal glands. One patient with oat cell carcinoma was alive with residual thoracic tumor and cervical lymph node metastasis 18 months after diagnosis.