Fine needle aspiration cytology of metastatic malignant granular cell tumour: a case report and review of the literature.

Granular cell tumour (GCT) is a benign soft tissue neoplasm considered to be of Schwann cell origin. Its malignant counterpart is extremely rare, accounting for 1-2% of all GCT. Traditionally, the presence of metastasis has been considered the most important criterion in defining malignancy. Although histological criteria for malignancy have been established, not all malignant GCT metastasize. While cytomorphological features of benign GCT have been well described, there are only a few reports of the cytology of malignant GCT. Herein, we detail a case of metastatic malignant GCT diagnosed on fine needle aspiration cytology (FNAC) with confirmation by histology, immunohistochemistry and ultrastructural studies. The literature on the cytomorphology of this rare entity is reviewed. [ABSTRACT FROM AUTHOR]