oat cell carcinoma [AS, ate, oat; L, cella, storeroom; Gk, karkinos, crab, oma, tumor] , a malignant, usually bronchogenic epithelial neoplasm consisting of small, tightly packed round, oval, or spindle-shaped epithelial cells that stain darkly and contain neurosecretory granules and little or no cytoplasm. Tumors produced by these cells do not form bulky masses but usually spread along submucosal lymphatics. Many malignant tumors of the lung are of this type. Surgical resection usually is not possible, and chemotherapy and radiation therapy are not effective in treatment; thus the long-term prognosis is poor. Also called small cell carcinoma.
