SMALL-CELL NEUROENDOCRINE CARCINOMA OF THE URINARY-BLADDER - A CLINICOPATHOLOGICAL STUDY WITH EMPHASIS ON CYTOLOGIC FEATURES

BACKGROUND. Primary small cell neuroendocrine carcinoma (SCNEC) of the urinary bladder is a rare but important entity. The authors have atte mpted to define the cytopathologic features of this tumor. METHODS. Si xty-one urine specimens (16 with histologic correlation) from 23 patie nts were studied. Twenty patients were male and 3 were female with an age range of 43 to 86 years (mean age, 68.8 years). Twenty-one cases w ere pure SCNEC and 2 were high grade undifferentiated carcinoma with n euroendocrine features. There were no false-positive or false-negative urine cytology diagnoses, but several cases of SCNEC were originally diagnosed as high grade transitional cell carcinoma by cytology. RESUL TS. Cytologic features of SCNEC included hypercellularity with isolate d single cells and clustered cells with naked hyperchromatic nuclei, f inely granular nuclear chromatin, rare nucleoli, and a high mitotic ka ryorrhectic index. Nuclear molding was prominent. No glandular formati on or nesting was noted. Half of the cases had a bloody, necrotic, or inflamed background. Histology, when available, was confirmatory in al l cases. CONCLUSIONS. Cytologic features of SCNEC are distinct and an accurate urinary cytologic diagnosis can be made. Differential diagnos is is limited and includes metastatic small cell carcinoma, high grade transitional cell carcinoma, and malignant lymphoma. (C) 1997 America n Cancer Society.