Investigation of basement membrane proteins in a case of granular cell ameloblastoma

Abstract

Granular cell ameloblastoma is a rare, benign neoplasm of the odontogenic epithelium. A case of massive granular cell ameloblastoma in a 44-year-old Thai female is reported. Histopathological features displayed a follicular type of ameloblastoma with an accumulation of granular cells residing within the tumor follicles. After treatment by partial mandibulectomy, the patient showed a good prognosis without recurrence in a 2-year follow-up. To characterize the granular cells in ameloblastoma, we examined the expression of basement membrane (BM) proteins, including collagen type IV, laminins 1 and 5 and fibronectin using immunohistochemistry. Except for the granular cells, the tumor cells demonstrated a similar expression of BM proteins compared to follicular and plexiform ameloblastomas in our previous study, whereas the granular cells showed strong positivity to laminins 1 and 5 and fibronectin. The increased fibronectin expression in granular cells suggests a possibility of age-related transformation of granular cells in ameloblastoma.

Figure 1

A clinical photograph of granular cell ameloblastoma in the oral cavity shows an enormous mass on the right mandible.

Figure 2

A panoramic radiograph displays a well defined multilocular radiolucency with scalloped border (arrowheads) extending from the right second mandibular premolar to the mandibular ramus. Extensive root resorption of the right second mandibular premolar and thinning of the cortical plate is detected. Note that the inferior alveolar nerve canal has been displaced inferiorly to the inferior cortex of the mandible (arrows).

Figure 3

Biopsy specimen reveals ameloblastomatous islands containing central large round cells with eosinophilic granules in the cytoplasm (hematoxylin and eosin stain, original magnification: ×200).

Figure 4

Immunohistochemical staining of basement membrane components, including laminin 1 (a), laminin 5 (b), collagen type IV (c) and fibronectin (d) in a granular cell ameloblastoma. (a) An intense staining of laminin 1 is found in the peripheral cells, central stellate shaped-like cells and granular cells. (b) A moderate-to-strong intensity of laminin 5 is seen in granular cells. (c) A strong expression of collagen type IV is detected at the basement membrane area surrounding tumor follicles. (d) A weak to moderate staining for fibronectin is observed in peripheral cells and central cells, whereas a moderate-to-strong staining is present in granular cells (immunostaining, original magnification: ×200).