Immunocytochemical study of small round cell tumors in routinely processed specimens

Fourteen commercially available monoclonal antibodies were used to examine, by the indirect immunoperoxidase technique, 20 formaldehyde solution-fixed, routinely processed bone marrow biopsy and surgical biopsy specimens from a group of small round cell tumors with bone marrow involvement, including 6 neuroblastomas, 4 rhabdomyosarcomas, 3 Ewing's sarcomas, 3 Burkitt's lymphomas, and 4 small-cell carcinomas of the lung. Eight of 14 monoclonal antibodies worked well on the routinely processed sections. Antidesmin (D33) (Dako Corp, Santa Barbara, Calif) and anti-muscle actin (HHF35) showed specific immunostaining in all 4 rhabdomyosarcomas included in this study. Anti-epithelial membrane antigen immunoreactivity was positive in all small-cell carcinomas of the lung. Anti-leukocyte common antigen (Dako) showed positive immunostaining in lymphomas and did not immunoreact with nonhematopoietic tumors. However, it was important to be aware that some lymphomas may not have been labeled with anti-leukocyte common antigen. All 6 neuroblastomas showed a positive immunoreactivity with anti-chromogranin A (LK2H10) and a weak reaction with antisynaptophysin (SY38). Panels of commercially available monoclonal antibodies, including anti-leukocyte common antigen, anti-epithelial membrane antigen, antidesmin (Dako), anti-muscle actin, and anti-chromogranin A, appear to be most useful in the differential diagnosis and staging of small round cell tumors on routinely processed biopsy specimens.