Granular cell tumors of the tongue: fibroma or schwannoma

BACKGROUND Granular cell tumors are benign lesions that typically occur in the oral cavity, but can also be found in other sites. However, the characteristics of these tumors are unclear. Thus, the present study aimed to investigate the immunohistological characteristics of these tumors of the tongue. METHODS Seven patients were treated for granular cell tumors of the tongue at our institution during 2003-2017. Paraffin-embedded specimens were available for all cases; thus, retrospective immunohistochemical analyses were performed. RESULTS All cases exhibited cytoplasmic acidophilic granules in the muscle layer of the tumor. Both the normal nerve cells and tumor cells also stained positive for PGP9.5, NSE, calretinin, and GFAP. A nucleus of tumor cells was typically present in the margin. The PAS-positive granules were also positive for CD68 (a lysozyme glycoprotein marker). Various sizes of nerve fibers were observed in each tumor, and granular cells were observed in the nerve fibers of a representative case. CONCLUSIONS Based on our immunohistological findings, granular cell tumors may be derived from Schwann cells, and the presence of CD68 indicates that Wallerian degeneration after nerve injury may be a contributor to tumor formation. Thus, a safe surgical margin is needed to detect the infiltrative growth of granular cell tumors.