Extra-Pulmonary Small Cell Cancer: Diagnosis, Treatment, and Prognosis

Abstract

Small cell carcinoma (SCC) is a high grade epithelial cancer of neuroendocrine origin, which is considered to be a distinct cinicopathological entity. It has been reported in the literature by using various terminologies including oat cell carcinoma, anaplastic carcinoma, small cell undifferentiated carcinoma, undifferentiated carcinoma, microcytoma, reserve cell carcinoma, small cell neuroendocrine carcinoma, Kulchitsky cell carcinoma, and carcinoma with amineprecursor uptake and decarboxylase (APUD) cell differentiation. Small cell carcinoma is, however, the recommended pathological term (Beasley et al., 2005). It is most commonly of bronchogenic origin and accounts for about 20–25% of all pulmonary malignancies (Hoffman et al., 2006). Small cell carcinoma of lung is well recognized for its aggressive clinical behavior and an increased propensity for early metastases. Uncommonly, SCCs can originate in non-pulmonary organs and are collectively known as “extrapulmonary small cell carcinoma” (Remick et al., 1987; Remick and Ruckdeschel, 1992). Extrapulmonary small cell carcinoma (EPSCC) often represents a diagnostic and therapeutic challenge. In 1930, it was first reported in the mediastinal glands without pathologic evidence of primary pulmonary involvement (Duguid and Kennedy, 1930). Since its first description, EPSCC has been reported in virtually all anatomical sites. The primary sites most frequently involved are gynecologic organs, especially the cervix; genitourinary organs, especially the urinary bladder and the prostate gland; the gastrointestinal tract, especially the esophagus, and head and neck region. In addition, SCC has been reported in the breast, thyroid, skin, and thymus gland. If the primary site remains undetected, these tumors are known as small cell carcinoma of unknown primary. Limited data are available regarding its clinical behavior and outcome. The available literature is predominantly based on reviews of published cases or analysis of institutional data (Remick and Ruckdeschel, 1992; Vrouvas and Ash, 1995). In general, EPSCCs resemble their pulmonary counterparts with respect to purported histogenesis, morphology, and behavior. The clinico-pathological features, diagnosis, and general management of EPSCC are reviewed here, followed by a brief description of