Ameloblastoma is a rare odontogenic tumor of the jaw that is benign but locally aggressive in nature. Broca in 1863 was the first to report as Adamantinoma, and then Churchill in 1934 suggested an alternate name called "ameloblastoma. “The World Health Organization (WHO) (1991) defined ameloblastoma as a benign but locally aggressive tumor with a high tendency to recur, consisting of proliferating odontogenic epithelium lying in a fibrous stroma. Ameloblastoma is most commonly seen in the posterior mandible, but may also arise in the maxilla and anterior aspect of the jaw. The radiographic appearance ranged from a unilocular to a multilocular radiolucency, soap bubble and honeycomb appearance. There are four different macroscopic subtypes: solid or multicystic, unicystic, desmoplastic and peripheral. This classification may have a prognostic value.

There are six histologic subtypes of ameloblastoma: follicular, plexiform, acanthomatous, granular, basal cell, and desmoplastic. They can be found combined or isolated and that are not related to the prognosis of the tumor. Ameloblastoma is rarely metastasizing

A 30-year-old female patient from a semi-urban area had reported to the Department of Oral Medicine & Radiology, MCDRC, Chhattisgarh, India, with the chief complaint of a painless swelling involving the left side of the lower jaw region for the past one and a half years. The swelling was slow-enlarging and asymptomatic. Initially, it was small in size but had grown gradually to attain the present dimension. She had a previous history of tooth extraction. The patient was of average height and weight. Extraoral examination revealed a diffuse swelling involving the left side of the body of the mandible. On palpation, the swelling was non-tender and firm in consistency. No regional lymph nodes were palpable. Intraoral examination showed the presence of a swelling involving the alveolar ridge of the mandible, extending from the 31 to 36 regions, with obliteration of the labial and lingual vestibules. On palpation, the swelling was firm, non-tender, and bony-hard in consistency. She had a gradual increase in swelling on the left side of the lower jaw, resulting in an obvious facial deformity.

The CBCT report revealed a well-defined solitary, multilocular osteolytic lesion in the left mandible, extending mesio-distally from 31 to 36 regions, labio-lingually to involve the entire alveolus, and supero-inferiorly from the crest to the mid-alveolus height. It measures approximately 30.3mm*19.3mm*33.2mm in its greatest dimensions. The presence of multiple locules was noted within the lesion (Honeycomb/soap bubble appearance), with the surrounding bone showing irregular marrow spaces and dense trabeculations extending posteriorly until 38. The septa within the lesion are thin. Buccal cortical plate expansion with multiple areas of bone perforations was noticed, along with thinning of the lingual cortex with few areas of perforation. Considering the history and clinical and radiological findings, a provisional diagnosis of ameloblastoma was made. Differential diagnoses included odontogenic myxoma, central giant cell granuloma, neurofibroma, central hemangioma, etc. An incisional biopsy was performed under local anesthesia, which was reported to be acanthomatous ameloblastoma. According to clinicopathological correlation, the features were corroborative of acanthomatous ameloblastoma. The patient was operated on under general anesthesia, and the tumor was resected, followed by the placement of a titanium plate as a temporary reconstruction to prevent derangement of the occlusion and obvious facial deformity. The patient is now planned for definite reconstruction by a microvascular-free fibula flap, dental implants, and further prostheses.

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Figure 1: A Preoperative Intraoral Photo Depicting the Swelling.

Figure 2: The CBCT Report Revealed A Well-Defined Solitary, Multilocular Osteolytic Lesion In The Left Mandible, Extending Mesio-Distally From 31 To 36 Regions, Labio-Lingually To Involve The Entire Alveolus, And Supero-Inferiorly From The Crest To The Mid-Alveolus Height.

Figure 3: Nest And Island of Epithelium with Peripheral Pallisading of Tall Columnar Cells with Reverse Polarity (H&E, 10X).

Figure 4: The Central Portion of The Island Shows a Loose Network of Reticular Cells. Squamous Metaplasia with Keratin Formation Is Seen in Reticular Cells (H&E, 40 X).

Figure 5: The Resected Tumor Specimen.

Figure 6: A Titanium Plate Was Placed After Segmental Mandibulectomy as A Temporary Reconstruction.

Figure 7: Follow-Up After 3 Months.

Figure 8: Follow-Up OPG After 3 Months.

Histopathological Report

An H&E-stained section reveals surface epithelium; the underlying stroma consists of lesional tissue. It consists of numerous small and large odontogenic islands, which are lined by ameloblasts like tall columnar cells with reversal of nuclear polarity, hyperchromatism, subnuclear vacuolization, and subepithelial hyalinization. These odontogenic islands show stellate reticulum-like cells within the lumen. Many islands exhibit squamous metaplasia of the stellate reticulum-like cells and the formation of large keratin pearls within the islands. The surrounding stroma is fibrocellular, consisting of bundles of collagen fibers, fibroblasts, and small capillaries.

An ameloblastoma is a true neoplasm of enamel organ-type tissue that does not undergo differentiation to the point of enamel formation [1]. It accounts for 1% of all the tumors of the jaw encountered from the third to the fifth decades of life, with no significant sex predilection [2]. Acanthomatous ameloblastoma occurs in older patients rather than in the younger population. The acanthomatous type of ameloblastoma is considered to be rare, with more involvement of the mandible (81%) than the maxilla (19%) [3]. In the present case, acanthomatous ameloblastoma was seen in a 30-year-old female patient involving the anterior mandible, extending to the body.

Patients with this neoplasm usually present with a slow-growing mass, malocclusion, loose teeth, pain, or, more rarely, paraesthesia; however, many lesions are detected incidentally on radiographic studies in asymptomatic patients. The lesions usually progress slowly but are locally invasive, will infiltrate through the medullary spaces, and can erode cortical bone. If left untreated, they can resorb the cortical plate and extend into adjacent tissue. In this case, the patient reported slowly progressive swelling and difficulty in mastication.Radiographically, ameloblastomas appear as radiolucent lesions that may either have a multilocular or unilocular, soap bubble/honeycomb type of appearance [4]. In later stages, they may expand the cortical plate, giving rise to a paper-thin appearance on a panoramic radiograph as well as on cone beam computed tomography (CBCT) [5].

Amongst the six histological subtypes, follicular ameloblastoma is the most prevalent histological variant (64.9%), followed by the plexiform (13.0%), desmoplastic (5.2%), and acanthomatous (3.9%) varieties. The histopathological features of an acanthomatous ameloblastoma include cells occupying the position of the stellate reticulum and undergoing squamous metaplasia, sometimes with keratin formation in the central portion of the tumor islands.6 In the present case, histopathological evaluation revealed the presence of islands of proliferating odontogenic epithelium containing a core of loosely arranged angular cells resembling stellate reticulum, surrounded by a single layer of tall columnar cells with nuclei showing reverse polarity, associated with squamous metaplasia and keratin production. Special investigations like Immunohistochemical analysis were not performed in this present case as the clinical, radiological, and histopathological findings were corroborative to the diagnosis of acanthomatous ameloblastoma. Therefore, a final diagnosis of acanthomatous ameloblastoma was made on the basis of clinical, radiological, and histopathological parameters. The treatment of choice is a complete surgical resection [6].

Ameloblastoma is an uncommon benign odontogenic neoplasm that rarely becomes malignant. To conclude, the definitive diagnosis is based on its histopathological appearance. Documentation and research in such cases may be helpful to correlate the prognosis of the lesions.

Funding

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Competing Interests

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