內文：
Aims
The aim is to present a case of rare giant granular cell ameloblastoma and to review the pertinent literature highlighting the molecular aspects of its pathogenesis by analyzing the expression of CD-68, Bcl-2, and β-catenin.
Introduction
Ameloblastoma is the second most common odontogenic tumor.
Several distinct clinical types, including solid, unicystic, desmoplastic, and peripheral ameloblastomas.
Ameloblastomas are further subclassified as follicular, plexiform, granular, basal cell, and acanthomatous.
Granular cell ameloblastoma (GCA) is a less common histological subtype of ameloblastoma.
Locally aggressive among all the ameloblastomas.
It is important to separate GCA from other ameloblastomas because of higher incidence of malignancy and metastases.
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.
Ameloblastomas can show slow and asymptomatic growth, because of this, patient seeks treatment only after the lesion has grown remarkably large size.
Neglected ameloblastomas may become enormous and cause gross facial deformities that pose considerable problems in management.
10 cases of giant ameloblastomas (3 cases of Follicular and 7 cases of plexiform) are reported till date. However, there are no cases of giant granular cell ameloblastomas reported.
Case Report
C.C.：A large painless swelling over the left side of the face.
P.I. ：A 39-year-old female patient reported to our hospital with a complaint of a large painless swelling over the left side of the face. She had first noticed the swelling 10 years ago which was painless with minimal extraoral manifestation.
The patient neglected the swelling due to its painless nature and slow growth.
Extra oral examination：
1. A large well-defined swelling measuring approximately 12 cm × 10 cm was found in the left cheek, mandible, and submental region.
2. Swelling was soft to firm in consistency with normal overlying stretched skin and no sinus or discharge observed.
Intra oral examination：
1. Massive swelling was noticed from tooth 31 to retromolar area, pushing the tongue to the contralateral side. Tongue movements were restricted.
2. Crowding and extrusion of lower left anterior and premolars were observed.
Radiographic examination：
There is a multilocular radiolucency, extending from left condyle and coronoid to right central and lateral incisors, with thinning of lower border
of mandible.
Surgically excised hemimandibulectomy specimen measured 12 × 9 × 10 cm and weighed 1200 grams. A follow-up of one year showed no recurrence.
Methods
Histopathological Analysis：
1. H&E stained sections showed large odontogenic islands showing peripheral ameloblast-like cells and central stellate reticulum-like cells with extensive granular cell transformation surrounded by fibrous stroma.
2. The granular cells exhibited coarsely granular eosinophilic cytoplasm and small pyknotic nuclei.
3. Therefore, a final diagnosis of ameloblastoma, granular cell variant, was given.Followed up for 1 year and showed no signs of recurrence.
Immunohistochemical Analysis：
1. Polyclonal rabbit anti-CD-68, anti-Bcl-2, and anti-β-catenin (Biogenix Life Sciences Limited, CA, USA) were used for immunohistochemistry employing the super sensitive polymer HRP detection system. The sections were later counter-stained with Mayer’s hematoxylin. The presence of brown color at the site of target antigen was considered as immunopositive.
2. The immunoreactivity was assessed based on staining intensity. The staining intensity of positive cells was evaluated visually and classified as follows: weak, moderate, and strong intensity. Finally localization of positively stained cells was also assessed, that is, in peripheral ameloblast-like cells, central stellate reticulum like cells, and granular cells.
Results
The tumor cells of granular cell ameloblastoma showed positive immunoreactivity to all proteins.
◎ CD-68 showed a moderate to strong staining intensity in granular cells.
◎ Moderate staining of Bcl-2 was expressed by the peripheral columnar cells of tumor islands and negative in the granular cells.
◎ Expression of β-catenin was generally weak, except for only the focal areas that showed a moderate staining intensity and weak in peripheral cells.
Discussion
This study reports a case of granular cell ameloblastoma that developed at the
All reports were of large tumors involving half of the mandible, and histological diagnosis in these ten cases was either follicular or plexiform type of ameloblastoma. To our knowledge, this is the first reported case of giant granular cell ameloblastoma.
The granular cells acquire small pyknotic nuclei and bulky cytoplasm filled with coarse eosinophilic granules indicating that there is an apoptotic process taking place. Several immunohistochemical studies showed increased apoptotic cells and decreased expression of antiapoptotic factors such as Bcl-2 and p53 proteins in granular cell ameloblastomas. Similarly in the present case, Bcl-2 expression was negative in granular cells.
In granular cell clusters, apoptotic cell fragments with condensed nuclei were phagocytosed by adjacent granular cells and degraded within lysosomes.
Therefore, granular cells show positivity for CD-68, lysozyme, and alpha-1-antichymotrypsin indicating cytoplasmic lysosomal aggregates.
Similarly in the present case, CD-68 expression was moderate to strong in granular cells.
Cell signaling pathways related to cell proliferation and differentiation are lost or inactive in the granular cells. Hence, the cell signaling molecules such as β-catenin, BMP-4, and Wnt-2 are altered in granular cells. Similarly in the present case, β-catenin expression was shown to moderate staining in granular cells.
Finally, the immunohistochemical results in the present case highlights that Bcl-2 negativity in granular cells indicating an apoptotic process, CD-68 positivity in granular cells indicating the presence of lysosomal aggregates and β-catenin cytoplasmic positivity in granular cells indicating an altered cell signaling pathways.
Granular cell ameloblastoma is locally aggressive and has a relatively high chance of recurrence. Recurrence rate for granular cell ameloblastoma was reported to be 33.3%, which is higher, compared to the more common follicular,
plexiform, and acanthomatous subtypes.
Conclusion
The present case of giant granular cell ameloblastoma is a rare entity. Development of monstrous size is indicative of ameloblastomas persistent growth. Granular cell transformation in ameloblastomas probably occurs as a consequence of extensive molecular changes occurring in central stellate reticulum-like cells.
Immunohistochemical studies help us to know the pathogenesis of this granular cell ameloblastoma. Therefore, an effort has been made here to study the expression of Bcl-2, CD-68, and β-catenin. Further studies on a large scale are essential for better understanding of the molecular pathogenesis of ameloblastoma and its subtypes in providing diagnostic and therapeutic benefits.
題號 題目
1
The histopathologic patterns of ameloblastoma are as follows EXCEPT：(A)
Follicular(B)
Plexiform(C)
Keratinized(D)
Desmoplastic答案(C) 出 處 ：
Oral and Maxillofacial Pathology, 2nd edition, p.613, Histopathologic Features of Ameloblastoma題號 題目
