Introduction
Salivary carcinoma, representing 3 to 4% of head and neck cancers, has garnered significant attention. Among these, mucoepidermoid carcinoma (MEC) emerges as the most prevalent subtype, exhibiting diverse clinical behaviours, from slow-growing to highly metastatic tumours. Predominantly, MEC affects larger salivary glands like the parotid, while in minor salivary glands, it commonly manifests on the palate, followed by other sites such as the retromolar gap, buccal mucosa, tongue, lips, floor of the mouth, sinuses, and larynx. Intraosseous mucoepidermoid carcinoma, originating in the gnathic bones, has long intrigued researchers due to its rarity. Theories about its origins, stemming from the neoplastic transformation of epithelial mucosa or ectopic salivary tissue, have circulated, yet its precise source remains uncertain.1 In 1963, Bhaskar2 studied mucoepidermoid tumours’ origin and composition. In 1991, the WHO renamed "mucoepidermoid tumour" to "mucoepidermoid carcinoma."3 Waldron and Mustoe4 later proposed including intraosseous mucoepidermoid carcinoma in primary intraosseous carcinoma of the jaw as type 4, enhancing our understanding of this neoplasm. (Table 1)
Imaging is crucial for detecting and distinguishing intraosseous mucoepidermoid carcinoma (IMC) due to its distinct features, such as a sclerotic periphery and a mixed internal structure. This structure often presents as a unilocular and/or multilocular pattern, sharing imaging characteristics with other lesions like ameloblastoma, glandular odontogenic cyst, and keratocystic odontogenic tumor. This case report emphasizes the significance of CBCT in accurately delineating the lesion and devising suitable treatment plans for IMC.
Case Description
A 55-year-old woman presented to the Oral Medicine and Radiology Department with a complaint of painful swelling in her lower left jaw, which had persisted for the past three months. The swelling had gradually increased following dental procedures, including the extraction of teeth 36 and 37 and the removal of a cyst a year prior. She had no significant medical history. After two weeks on medication following her hospital visit, a general examination revealed that she had a normal gait, build, and well-nourished appearance with normal vital signs.
Figure 1
Intraoral image shows h ard, tender swelling, approximately 3 by 4 cm, extended from the second premolar, involving the ramus and mandibular body. Dilated vessels covered its surface with obliteration of the buccal vestibule.
Figure 2
Panoramic radiograph depictsirregular, lobulated, expansile osteolytic lesion, approximately 3*4cm in size, extending from the distal aspect of the 2nd premolar to the ramus and coronoid process posteriorly.
Figure 3
Cone beam computed tomography (CBCT) sections shows a single, well-defined hypodense lesion with septations is seen on the left side of the mandibular body and ramus extending from the area of tooth 36 to the ascending ramus, resulting in expansion and thinning of the lingual and buccal cortical plates. (A) Axial (B) Sagittal (C)Coronal D) 3D CBCT.
Figure 4
Given H/E-stained section showed glandular component with severe dysplastic changes along with disruption of septate and mucoid content in some ducts. Background also shows presence of epidermoid cells, intermediate cells, and mucous cells with areas of degenerated bony trabeculae.
Table 1
Classification of primary intraosseous carcinoma (PIOC)
Table 2
Differential diagnosis of intraosseous mucoepidermoid carcinoma
Externally, there was mild facial asymmetry on the left mandibular side due to a diffuse swelling measuring approximately 3 by 4 cm, extending from the mandibular body to the ramus. The swelling had a bony hard consistency and was non-tender upon palpation. Additionally, the left submandibular glands were enlarged and tender.
Intraorally, a diffuse, bony hard, and tender swelling measuring approximately 3 by 4 cm was noted, with dilated vessels over its surface. This swelling involved the ramus and mandibular body from the second premolar region onwards, causing obliteration of the buccal vestibule and extending from the alveolar ridge to the inferior border of the mandible. Mild expansion of the buccal and lingual cortices was observed (Figure 1).
Panoramic radiography revealed an irregular, lobulated, expansile osteolytic lesion, approximately 3 by 4 cm in size, extending from the distal aspect of the second premolar to the ramus and coronoid process posteriorly. Based on the clinical examination, the provisional diagnosis was a residual cyst (Figure 2). Lab findings showed hemoglobin at 10.6 gm%, random glucose at 123 mg/dl, with other parameters being normal. Further investigation with a cone beam computed tomography (CBCT) of the mandibular region showed a single, well-defined hypodense lesion with septate in the left side of the mandibular body and ramus. The lesion spanned antero-posteriorly from the area of tooth 36 to the ascending ramus, leading to the expansion and thinning of the lingual and buccal cortical plates. Measuring approximately 43.1 mm anterioposteriorly, 16.2 mm bucco lingually, and 17.5 mm superioinferiorly , it had an irregular shape with a multilocular appearance internally. The surrounding structures displayed a discontinuity in the superior border of the inferior alveolar canal in the regions of teeth 37 and 38, alongside significant thinning and expansion of the lingual cortical plate. The buccal cortical plate was discontinuous in regions 36 and 37, and thin and expanded elsewhere, while the inferior border of the mandible appeared intact (Figure 3 a, 3b, 3c, 3d). The radiographic differential diagnosis was considered as ameloblastoma, odontogenic keratocyst, odontogenic myxoma, aneurysmal bone cyst, and central giant cell granuloma explained in detail. (Table 2)
Finally, an excisional biopsy was performed, and histopathological examination revealed the presence of a glandular component with severe dysplasia, epidermoid cells, intermediate cells, and mucous cells along with disintegrated bony trabeculae, suggestive of intraosseous mucoepidermoid carcinoma (Figure 4).
Discussion
In 1945, Stewart and colleagues provided a detailed description of the mucous-secreting and epidermal cellular components of a specific pathological condition, establishing it as a distinct entity.5 Additionally, Lepp's 1939 report6 on the first case of intraosseous mucoepidermoid carcinoma (MEC) of the mandible ignited further investigation into its histological makeup and how tumors of this type develop. IMC is a rare bone tumour with only 136 reported cases in English literature since its first description.7
The mandible, particularly its posterior section, is frequently where intraosseous MECs are found. This condition affects women more often than men, and although it typically occurs in individuals aged between their fourth and fifth decades, cases have been documented in patients ranging from their first to seventh decades. Our cases align with the patterns observed in existing literature. Common symptoms of intraosseous MEC include painless swelling in the oral cavity, pain, tingling sensations, numbness, and loose teeth.8
Etiopathogenesis
The etiology of this lesion remains uncertain, yet various theories attempt to elucidate its origins. Potential explanations include:
Persistence of ectopic salivary gland tissue, remnants of embryonic salivary glands entrapped within bone.
Transformation of mucous cells present in odontogenic cysts.
Intraosseous extension of maxillary sinuses or submucosal and mucosal glands.9
An alternative interpretation posits the integration of salivary glands into the developing mandible.10 (Figure 5)
However, Imaging is crucial for detecting and distinguishing MEC due to its sclerotic periphery and varied internal structure, resembling patterns seen in other lesions like ameloblastoma, Odontogenic keratocyst, odontogenic myxoma, Squamous cell carcinoma, Central giant cell granuloma and aneurysmal bone cysts. According to Chan et al, 11 radiographic features of the IMC include well- defined sclerotic margins with an amorphous internal sclerotic bone and several minor locules. Additionally, the aggressive nature of the tumour showed by cortical bulging, perforation of the cortical bone, and invasion of the tumour to surrounding soft tissues, with the displacement of the tooth and root resorptions.7 Brookstone and Huvos12 proposed a three-grade classification for IMC:
Grade 1: Absence of cortical plate expansion or rupture.
Grade 2: Cortical plate expansion occurs without rupture.
Grade 3: Cortical plate rupture or presence of regional metastasis.
However, panoramic radiography does not allow as assessment of destructive bone lesions with non-uniform border or with degrees of extension and invasion into the surrounding tissues, nor enough to differentiate this kind of tumour from an odontogenic cyst or ameloblastoma. On the other hand, CT offers a large amount of information on size, location, and area of the tumour in the region.13 Diagnostic criteria for intraosseous MEC were defined by Alexander et al. and modified by Browand and Waldron and are as follows:14
Intact cortical plates on CT
Radiographic evidence of bony destruction
Exclusion of another primary tumor whose metastasis could histologically mimic the central tumor
Exclusion of an odontogenic tumor
Histopathologic confirmation
Detectable intracellular mucin
These lesions are typically treated with radical resection of adjacent normal bone margins. In some cases, neck dissection and post-operative radiation therapy are necessary. In our case, the lesion was treated with radical resection followed by adjuvant radiotherapy.
Conclusion
This case emphasizes the importance of recognizing and managing malignant tumors arising from odontogenic cysts. Thorough surgical intervention, supplementary treatments, and histopathological analysis are crucial. CBCT helps differentiate intraosseous Mucoepidermoid Carcinoma from primary dentigerous tumors, facilitating timely diagnosis and treatment planning, ultimately enhancing patient outcomes.
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