Granular Cell Ameloblastoma: an Unusual Histological Subtype Report and Review of Literature

Abstract

BackgroundGranular cell ameloblastoma is a rare histological subtype of ameloblastoma accounting for less than 5% of the total. The characteristic microscopic features of granular cells are attributed to the increased presence of lysosomes in the cytoplasm of the tumour cells.MethodsA case of bone expansion in the mandible of 65 year old patient was examined on the basis of the clinical examination, radiographic imaging and microscopic features. A complete surgical removal was performed.ResultsThe radiographic imaging characteristics were consistent with a locally aggressive jaw lesion. Histological examination of the tumour revealed typical features of granular cell ameloblastoma. The specimen margins were free of tumour and the postoperative course was uneventful. No evidence of recurrence was noticed during a 1.5 years follow-up period.ConclusionsThe rarity of the granular cell ameloblastoma subtype and the possibility of confusion with other odontogenic and non-odontogenic lesions with a granular cell component require an understanding of the salient features of this locally aggressive neoplasm. A literature review is provided focusing on emerging molecular parameters in the pathogenesis of these tumours and the differential diagnosis of oral lesions featuring granular cells.

Granular cell differentiation: A review of the published work

“…Ameloblastoma is a benign odontogenic tumor that originates almost exclusively in the jaw, often in the posterior mandible, resulting in pain and swelling. It histologically demonstrates peripheral columnar cells with hyperchromatic, reversely polarized nuclei, arranged in a palisaded pattern . This tumor also has a rare, granular cell subtype and, like the tumors described above, the granules represent the accumulation of lysosomes as a result of degenerative changes .…”

“…Likewise, the granular cell ameloblastoma reportedly behaves the same as the archetypal variant, which is locally aggressive with a high rate of recurrence . Immunohistochemical analysis for granular ameloblastoma is reportedly positive for CK, CD68, lysozyme and α1‐antichymotrypsin, but negative for vimentin, desmin, S100 protein and NSE and CD15, indicating epithelial origin and lysosomal aggregation . Although classical GCT often arise in the mouth, they can be easily differentiated from granular ameloblastoma via clinical presentation and immunohistochemical studies.…”

Extra-tongue oral granular cell tumor: Histological and immunohistochemical aspect

“…Schwanomas (28), melanocytic nevi (29), ameloblastomas (30), and metastatic lesions can also show a granular cell proliferation, but it is usually only a focus or an area of the tumor showing this feature ( Table 2). …”

Rare Giant Granular Cell Ameloblastoma: A Case Report and an Immunohistochemical Study

“…This “granular change” is thought to be due to a dysfunctional status of neoplastic cells, and the pathogenesis of this tumor seems to be age related. Thus, acquisition of granular cell phenotype has been attributed to an aging or degenerative change in long-standing lesions [4]. …”