|Year : 2013 | Volume
| Issue : 4 | Page : 148-150
Infiltrating lipoma of oral cavity: A rare entity
Syed Wali Peeran1, Karthikeyan Ramalingam2, Fatma Mojtaba Alsaid3, Marei Hamed Mugrabi4
1 Department of Periodontology and Oral Implantology, Sebha University, Sebha, Libya
2 Department of Oral Pathology and Microbiology, Sebha University, Sebha, Libya
3 Faculty of Dentistry, Sebha University, Sebha, Libya
4 Department of Periodontics, Faculty of Dentistry, Arab Medical University, Benghazi, Libya
|Date of Web Publication||4-Dec-2013|
Department of Oral Pathology and Microbiology, Faculty of Dentistry, Sebha University, Sebha
Source of Support: None, Conflict of Interest: None
Introduction: Lipomas are rare in the oral cavity comprising less than 5% of benign neoplasms in head and neck region. Infiltrating lipomas are much less common than other variants. Case Report: We report a rare case of infiltrating/intra-muscular lipoma in the retro-molar region of a 28-year-old male. Discussion: To the best of our knowledge, this is the first case report from Libyan population and in the Middle East & North Africa region (MENA). Surgical excision is curative but, regular follow-up is needed to identify recurrences of this unusual variant.
Keywords: Infiltrating lipoma, libyan origin, oral cavity, retro-molar region
|How to cite this article:|
Peeran SW, Ramalingam K, Alsaid FM, Mugrabi MH. Infiltrating lipoma of oral cavity: A rare entity. Dent Hypotheses 2013;4:148-50
| Introduction|| |
Lipomas are defined as benign neoplasms of mature fat tissue.  Despite being the most common mesenchymal neoplasm in adults, the occurrence of lipomas in the oral cavity is uncommon, representing only 1-5% of all oral neoplasms. Lipomas may occur in any intra-oral location, but the most commonly reported sites are the buccal mucosa, tongue, floor of mouth, buccal vestibule, lip, palate, gingival, and retromolar area. , They usually present as painless, well-circumscribed, slow-growing submucosal or superficial lesions.  There are a number of microscopic subtypes of lipoma, such as angiolipoma, fibrolipoma, myolipoma, chondroid lipoma, spindle cell lipoma, myxoid lipoma, and pleomorphic lipoma. Lipomas can be classified as classic or simple lipoma which could be heterotopic like intra-muscular and inter-muscular location. 
There are less than 10 reported cases in literature about the infiltrating variant of lipoma in head and neck region. ,,,,, We report this case of infiltrating lipoma because of its rarity and the atypical features. To the best of our knowledge, this is the first case report in Libyan population and to be reported from the MENA region. The purpose of presenting this case is to highlight the distinctive manifestation of this lipoma variant.
| Case Report|| |
A 28-year-old, apparently healthy male patient of Libyan origin was referred to the outpatient department, Faculty of Dentistry, Sebha University, Sebha, Libya for examination of swelling in the oral cavity. History revealed that the patient had noticed the swelling few months earlier. It started as a small swelling and grew slowly to attain the present size. The swelling was asymptomatic but interfered with mastication. Medical, surgical, and dental histories were non-contributory. Family history was irrelevant.
Clinical examination revealed a pedunculated swelling arising from the left buccal mucosa in the retromolar region, approximately 3 × 2 cms in size and covered by apparently normal mucosa. There was evidence of occlusal trauma in few areas. On palpation, the swelling was soft to fibro-elastic in consistency with diminished mobility at the base of the swelling [Figure 1]. Provisionally, it was diagnosed as lipoma.
|Figure 1: Intra-oral picture showing the swelling in the left retro-molar region|
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The lesion was surgically excised with a margin of normal tissue under local anaesthesia, fixed in formalin and sent for histopathological assessment.
Grossly, the tumor was a round, well-circumscribed mass about 2.5 cms in diameter [Figure 2]. The colour of the mass varied from predominantly yellowish-brown and soft to firm consistency on palpation. Histopathology of the tumor revealed mature adipocytes with thin, fibrous connective tissue septa [Figure 3]. Deeper sections revealed infiltration of the muscle without any evidence of degeneration [Figure 4].
|Figure 3: Photomicrograph showing mature adipocytes separated by thin fibrous connective tissue septa (H and E, ×10)|
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|Figure 4: Photomicrograph showing the adipocytes infiltrating the muscle bundles (H and E, ×10)|
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Correlating the history, clinical examination, and biopsy report, the lesion was diagnosed as infiltrating lipoma.
The patient is remaining disease-free on follow-up for the past one year after surgical excision.
| Discussion|| |
The common inter-muscular type or the rarer intra-muscular form is considered a heterotopic variant of the classic lipoma, if it grows between two or more distinct muscles or any other known histological type of lipoma, which exhibits inter-digitations with the muscle fibres. , There are doubts regarding their existence, as simple lipomas may be entrapped between muscle fibers.  The tendency to infiltrate muscle fibers could lead to recurrence of these variants. 
The infiltrating behavior of these variants should be excluded from liposarcoma. However, well-differentiated liposarcomas are usually encapsulated and they have the tendency to lose the connective sheath as they gain a more aggressive behavior. Infiltrating lipomas infiltrate the muscular bundles from the periphery.  Histologically, the presence of intact muscular fiber in the context of the lesion and the absence of cellular atypia and lipoblasts should confirm the diagnosis of an infiltrating lipoma. 
The superficial lipomas can be accurately diagnosed with clinical examination. The differential diagnosis of superficial lesions includes Schwannoma, neurofibroma, vascular malformation, sebaceous cyst, and lymphangioma. The deeper lipomas should be assessed by magnetic resonance imaging (MRI) or computed tomography (CT) with appropriate contrast. 
Our case correlated with literature exhibiting a slow growth, being larger in size and deeply localized than simple lipomas. Our case did not have any sensory disturbances due to pressure or tension on nerve trunks.  The most common reported location for intra-muscular lipomas in the oral cavity is the tongue,  but our case presented in the retro-molar region.
In addition to the oral cavity, this variant of infiltrating lipoma usually affects the large muscles of the extremities in adult men; it is usually painless and characterized by infiltrating adipose tissue and muscle atrophy. At these sites, the recurrence rate after surgical resection is higher,  whereas, it rarely recurs in the oral cavity after complete removal. , Surgical excision of the lipoma is curative and recurrence is rare. However, infiltrating lipomas have a high recurrence rate and the patients must be followed-up at regular intervals.  But our patient is remaining disease-free on follow-up.
The exact pathogenesis of lipomas is still controversial. There are reports on the presence of chromosomal abnormalities translocations involving 12q13-15, locus interstitial deletions of 13q and rearrangements involving 8q11-13 locus.  It could also arise by pre-adipocyte differentiation and proliferation mediated by cytokines following soft tissue damage when blunt trauma and hematoma formation occurs. Further studies are needed for clarification. 
| Conclusion|| |
The lipoma is an extremely rare tumor of the head and neck region. We report a rare case of infiltrating lipoma involving the retro-molar region. Surgical excision is curative but, regular follow-up is needed to identify recurrences of this unusual variant.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]