| Abstract|| |
Ameloblastoma is a neoplasm of odontogenic epithelium, especially of enamel organ-type tissue that has not undergone differentiation to the point of hard tissue formation. Granular cell ameloblastoma is a rare condition, accounting for 3-5% of all ameloblastoma cases. A 30-year-old female patient presented with the chief complaint of swelling at the right lower jaw region since 1 year. Orthopantomogram and computed tomography scan was suggestive of primary bone tumor. Histopathologically, diagnosis of granular cell ameloblastoma of right mandible was made.
Keywords: Ameloblastoma, granular cell, odontogenic tumor
|How to cite this article:|
Jansari TR, Samanta ST, Trivedi PP, Shah MJ. Granular cell ameloblastoma of mandible. Indian J Pathol Microbiol 2014;57:305-7
| Introduction|| |
Ameloblastoma is the most significant epithelial odontogenic tumor of concern for the oral pathologist due to its high incidence among all odontogenic tumors and true neoplastic (infiltrative and recurrent) potential, combined with its varieties of histologic patterns. Granular cell ameloblastomas are uncommon lesions accounting for about 3-5% of all histologic subtypes of ameloblastoma. Granular cells are a transitional or matured phase in the life cycle of ameloblastomas, starting with normal stellate reticulum like cells, leading to a production of granules and finally leading to degeneration and formation of cystic areas. 
Here, we present a rare case of granular cell ameloblatstoma in a 30-year-old female highlighting its unique microscopic features.
| Case report|| |
A 30-year-old female patient presented with a swelling at the right lower jaw which was gradually increased in size since 1 year. On clinical examination, the swelling was bony hard involving right lower alveolus measuring 10 cm × 10 cm × 7 cm, grossly extending up to the floor of the mouth medially and retro molar trigone posteriorly. Right side cervical lymph nodes of level I to IV were enlarged. All biochemical and hematological reports were within the normal limits.
Orthopantomogram was showing the presence of an expansile lytic lesion involving right side of the body of mandible with soap bubble appearance [Figure 1]a]. Possibility of primary bone tumor was suggested.
|Figure 1: (a) Orthopantomogram showing the presence of lytic lesions involving right side of mandible. (b) Computed tomography scan showing large, expansile, lytic lesion involving right side body, angle, and ramus of mandible|
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Computed tomography scan showed large, expansile, lytic lesion involving right side body, angle, and ramus of mandible measuring 8 cm × 7 cm × 6 cm with associated large soft tissue component. The lesion showed internal well-defined nonenhancing areas suggestive of internal areas of necrosis. The lesion extended up to the right side floor of mouth and displaced muscles of it. It compressed and displaced the right submandibular salivary gland [Figure 1]b]. Possibility of primary bone tumor was suggested. The punch biopsy was taken and reported as ameloblastoma, granular cell type.
Right segmental mandibulectomy with reconstructive surgery was performed. Grossly, a lesion was involving body and ramus of the mandible measuring 11 cm × 7 cm × 5 cm having solid and cystic cut surface [Figure 2]. The cyst was unilocular, containing red brown fluid. Two grossly unremarkable lymph nodes having a diameter of 2 cm and 1 cm, respectively, were dissected.
|Figure 2: Gross appearance of the granular cell ameloblastoma of mandible showing cystic and solid cut surface|
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Microscopically, tumor showed predominantly follicular pattern, center part showed sheets of large eosinophilic granular cells having abundant coarse granular eosinophilic cytoplasm and peripherally situated nucleus. Periphery of follicle showed tall columnar hyperchromatic cells resembling ameloblast-like cells. The connective tissue stroma was loose and well vascularized [Figure 3]. Pleomorphism and mitosis were absent. Focal plexiform pattern was also evident. The final diagnosis of granular cell ameloblastoma was given. Two dissected lymph nodes showed reactive follicular hyperplasia. All mucosal resection margins were free of tumor. Patient is on regular follow-up and is free of disease until date.
|Figure 3: Granular cell ameloblastoma. (a) A large ameloblastic follicle with granular cell change at the center (H and E, ×10). (b) Polygonal tumor cells having eosinophilic granular cytoplasm with eccentrically|
placed nuclei (H and E, ×40)
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| Discussion|| |
The granular cell ameloblastoma is an unusual variant showing marked transformation in the cytoplasm of tumor cells, which are usually stellate reticulum-like cells. The transformed cells possess very coarse, granular, and eosinophilic cytoplasm. 
Reichart et al. reviewed all available literature on ameloblastoma of the jaws from 1960 to 1993 and reported that of a total of 1593 cases with available data on histological subtypes, there were only 56 (3.5%) cases of the granular cell variant. 
Previous literatures on ultrastructural and immunohistochemical studies of cytoplasmic granules of tumor cells have revealed that they are lysosomal aggregates.  Lysosomal aggregation within the cytoplasm is caused by dysfunction of either a lysosomal enzyme or lysosome-associated protein involved in enzyme activation, enzyme targeting or lysosomal biogenesis. These defects lead to the accumulation of substrate that would normally be degraded in the endosome-lysosome system. 
Sathi et al. suggested that the synthesis of signaling molecules, such as β-catenin and Wnt-5a is upregulated in the granular cells of granular cell ameloblastoma, but their transportation or secretion is impaired, resulting in their accumulation within granular cells, as autophagosomes. 
The granular appearance of the tumor cells can be seen in various oral tumors, such as granular cell ameloblastoma, granular cell myoblastoma, congenital epulis and granular cell ameloblastic fibromas. The morphology of all granular cells is similar, but their origins are different. As per histogenesis, granular cell ameloblastoma is epithelial, while others appear to be of mesenchymal origin. 
Hartman has reported a series of 20 cases of granular cell ameloblastoma and emphasized that this granular cell type appears to be an aggressive lesion with a marked proclivity for recurrence and metastasis. Thus, recognizing this variant of ameloblastoma definitely has an important role in the treatment plan. 
The recurrence rate of the granular cell variant was 73% in the Armed Forces Institute of Pathology series for all modes of therapy combined.  Few cases of metastasis have also been reported in the literature. ,,
On the contrary to the old belief that granular cell ameloblastoma is the most aggressive variant of ameloblastoma, the findings of one study demonstrated it to be a myth. 
Hence, whether granular cell change in ameloblastoma is a degenerative process or a harbinger of a more aggressive course is a matter of debate. 
| Conclusion|| |
Granular cell ameloblastoma is a rare condition with unique histopathological features. Early diagnosis and prompt surgical treatment are of prime importance. Noteworthy is that, granular cell ameloblastoma may rarely behave in malignant fashion, giving rise to metastasis. Patients should be kept under periodic observation because of reports of recurrences even up to 8 years after initial treatment.
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Trupti R. Jansari
Room No. 412, Department of Pathology, The Gujarat Cancer And Research Institute, Civil Hospital Campus, Asarwa, Ahmedabad - 380 016, Gujarat
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]