Granular cell tumor: Case report.

Granular cell tumor is a rare benign soft tissue tumor of Schwann cell origin. It shows a predilection for the oral cavity, especially the dorsal surface of the tongue. Here, we presented a granular cell tumor at the right lateral border of the tongue of a 41-year-old male patient.

This 41-year-old male patient came to our oral and maxillofacial surgery clinic for evaluation of a mass at the right lateral border of the tongue for several weeks. Intraoral examination did not reveal any elevated tumor at the right lateral border of the tongue, but a firm mass measuring approximately 1.0 cm in greatest dimension was palpable at the submucosal area of the right lateral border of the tongue. The tumor was painless. Because the origin of the tumor was uncertain and the tumor was relatively small, the tentative treatment plan was total excision of the tumor. After discussing with the patient and obtaining the signed informed consent, the tumor was totally excised under local anesthesia. The removed soft tissue tumor specimen was sent for histopathological examination. Microscopically, the tumor was covered by slightly hyperplastic parakeratinized stratified squamous epithelium (Fig. 1A). The medium- and high-power views showed sheets or nests of large, polygonal tumor cells with abundant slightly basophilic and granular cytoplasm and vesicular nuclei infiltrating among skeletal muscle fibers (Fig. 1B and C). The cell borders were indistinct and some cells seemed to fuse together to show a syncytial appearance (Fig. 1C). Immunohistochemical stain revealed that the tumor granular cells were positive for S-100 protein, suggestive of nerve tissue origin (Fig. 1D). The above-mentioned characteristic findings finally confirmed the histopathological diagnosis of a granular cell tumor.

Figure 1

Histopathological and immunostained microphotographs of our case of granular cell tumor. (A) Low-power microphotograph exhibiting that the tumor was covered by slightly hyperplastic parakeratinized stratified squamous epithelium (Hematoxylin and eosin stain or H&E; original magnification, 4×). (B and C) Medium- and high-power microphotographs demonstrating sheets or nests of large, polygonal tumor cells with abundant slightly basophilic and granular cytoplasm and vesicular nuclei infiltrating among skeletal muscle fibers. The cell borders were indistinct and some cells seemed to fuse together to show a syncytial appearance (C) (H&E; original magnification; B, 20×; C, 40×). (D) Immunostained microphotograph showing that the tumor granular cells were positive for S-100 protein. (Immunostain; original magnification, 20×).

A significant microscopic finding of granular cell tumor is pseudoepitheliomatous hyperplasia of the overlying epithelium, which has been reported in up to 50% of all granular cell tumors. However, our case did not show this specific finding. For granular cell tumor, the most commonly used immunostain is the anti-S-100 protein immunostain and the granular cells in our case were positive for S-100 protein. The tumor cells of granular cell tumors are also positive for other biomarkers such as CD68, calretinin, and neuron-specific enolase.1, 2, 3, 4 Kurtin and Bonin reported CD68 positivity in neoplastic cells of all 27 granular cell tumors and 4 of the 5 schwannomas, indicating an intimate histogenetic relationship between granular cell tumors and Schwann cells. The CD68 positivity also suggests that the granular cells in granular cell tumors have phagocytic activity. Fine and Li demonstrated that 40 (93%) of 43 granular cell tumors are positive for calretinin. The expression of calretinin, a primarily neuronal protein, in granular cell tumors further supports its neural differentiation or derivation. The concomitant presence of a constant diffuse positivity for both S-100 protein and neuron-specific enolase in 11 granular cell tumors also suggests the neuroectodermic nature of the granular cell tumor. The granular cell tumor is best treated by conservative local excision, and recurrence is rare, even when the tumor is not completely removed.

Declaration of competing interest

The authors have no conflicts of interest relevant to this article.