Aspiration cytology, immunocytochemistry and electron microscopy of a malignant peripheral neuroectodermal tumor. A case report.

The findings of fine needle aspiration (FNA) cytology, immunocytochemical staining and electron microscopy (EM) in a case of malignant peripheral neuroectodermal tumor (PNET) presenting as a soft tissue mass in the lateral abdominal wall are reported. The immediate evaluation of the aspirate revealed cells of a small round cell malignant tumor. To provide a specific preoperative diagnosis, additional cytologic material was aspirated for immunocytochemical and ultrastructural investigations. While the results of EM were nonspecific, allowing only the exclusion of other small round cell malignancies, immunocytochemical staining of the aspirate was suggestive of a PNET. The diagnosis of PNET was corroborated by histopathologic and immunohistochemical findings. This case indicates that an exact preoperative categorization of small round cell malignant tumors can be made by FNA biopsy in otherwise equivocal cases when immunocytochemical and ultrastructural techniques are also utilized.