Small round cell tumors of the abdomen and thorax. Role of fine needle aspiration cytologic features in the diagnosis and differential diagnosis.

OBJECTIVE: To evaluate the role of cytomorphologic features in the diagnosis and differential diagnosis of small round cell tumor (SRCT) of the abdomen and thorax. STUDY DESIGN: During a period of six years (1985-1990), ultrasound/ computed tomography-guided fine needle aspiration cytology was performed on thoracic and abdominal/ pelvic masses in 899 cases. Slides were not available for review in 28 cases. Review of smears by one of the investigators (D.K.D.) in the remaining cases, which included 239 with intrathoracic and 632 with intraabdominal/pelvic masses, yielded 380 (43.6%) cases of malignancy. Of these, 71 (18.7%) cases were small round cell tumors. In 59 cases of SRCT the smears were found suitable for detailed assessment of cytomorphologic features. RESULTS: The 59 cases of small round cell tumors included 5 cases of neuroblastoma, 7 of hepatoblastoma, 4 of nephroblastoma, 1 of pulmonary blastoma, 2 of Ewing's sarcoma, 23 of non-Hodgkin's lymphoma (NHL), 15 of small cell anaplastic carcinoma (SCAC), 1 NHL/ SCAC and 1 small round cell tumor (not otherwise specified). The frequencies of rosettes (60%) and filamentous/fibrillar matrix (100%) in neuroblastoma; acinar formation in hepatoblastoma (100%) and SCAC (93.3%); tubule formation in nephroblastoma (100%); lipid vacuoles (69.6%), exclusive noncohesive cells (95.7%) and lymphoglandular bodies (87%) in NHL; and nuclear molding (100%) and paranuclear blue inclusions (60%) in SCAC were significantly higher as compared to the rest of the SRCTs (P<.01 to <.0001). CONCLUSION: The various cytomorphologic features, alone or in conjunction with other cytologic features, and clinical/imaging findings are very useful in the diagnosis of specific types of SRCT.