OBJECTIVETo observe the common characteristics of pathological morphology and immunohistochemical staining of olfactory neuroblastoma (ONB), and to raise the diagnostic ability for ONB.

METHODS34 cases of ONB, 11 cases of rhabdomyosarcoma (RMS) and 76 cases of malignant lymphoma (ML) were collected, the clinical information were investigated, and the biopsy samples were stained and observed as follows: (1) Routine HE staining and viewed under the light microscope. (2) Expression of neuron-specific enolase (NSE), chromogranin-A (CgA), leukocyte common antigen (LCA), desmin, and sarcometic actin (S-actin) were determined in both ONB and RMS cases. In addition, S-100 protein, cytokeratin (AE1/AE3) were detected in the ONB and myoglobulin detected in the RMS. ML samples were stained for LCA, CD45RO, CD56, and CD20. The NSE, CgA, desmin and S-actin were stained in 10 cases of NK/T cell ML and 9 cases of B cell ML additionally. (3) 4 cases of ONB, RMS and ML were observed under transmission electron microscope respectively.

RESULTSThe ages and clinical manifestations of ONB, RMS and ML were similar. The morphological characteristics of ONB included epithelial nests; net of angioma-like fibrous connective tissues; small round cells and small short spindle cells and nucleus; glandular and squamous liked epithelium; Homer-Wright and Flexner rosette; bunch of neurofibrilla, etc. NSE and CgA were expressed in small cells. S-100 protein was positive in the area of bunch of neurofibrilla. AE1/AE3 was positive in epithelial cells, LCA, while desmin and S-actin were all negative. Ultrastructurelly, there were neurosecretory granules and neurofibrilla in the cytoplasm of a few tumor cells. Although there were some similarities among ONB, RMS and ML under the light microscope, their characteristics of pathologic morphology, immunohistochemical staining and transmission electron microscope were different.

CONCLUSIONSThe features of the morphological changes are the most important basis to make diagnosis for ONB. The results of immunohistochemical staining can verify it further and play an important role in its differential diagnosis. Transmission electron microscope is very important but not essential for its diagnosis.