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An Official Publication of the Indian Association of Oral and Maxillofacial Pathologists


 
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ONLINE ONLY - CASE REPORT  
Year : 2022  |  Volume : 26  |  Issue : 1  |  Page : 129-130
 

Parosteal lipoma of the mandible: A case report and review of the literature


Department of Oral and Maxillofacial, University Hospitals Bristol and Weston, Bristol Dental Hospital, Lower Maudlin Street, Bristol, UK

Date of Submission06-Jun-2021
Date of Decision24-Nov-2021
Date of Acceptance24-Jan-2022
Date of Web Publication31-Mar-2022

Correspondence Address:
Julie Potter
Victoria Hospital, NHS Fife, Hayfield Road, Kirkcaldy, KY2 5AH
UK
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jomfp.jomfp_179_21

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   Abstract 


Introduction: Lipomata are soft-tissue mesenchymal neoplasms that are benign in nature and often asymptomatic. Lipomata commonly occur in the body, however, only 1%–5% are identified within the oral cavity, and lipomata with osseous metaplasia account for <1% of all lipomata.
This report describes a patient presenting with an ossifying lipoma with parosteal localization at the mental protuberance. This is followed by review of the current literature for this rare entity.
Materials and Methods: A PubMed literature review designating search terms including “oral” and “parosteal lipoma” or “lipoma with osseous metaplasia” or “ossifying lipoma” or “osseous lipoma” was conducted.
Results: The literature review identified two previous reports of parosteal localization of lipomata in the mandible and 22 cases of lipomata with osseous metaplasia within the oral cavity.
Conclusions: With the initial suspicion of a more malevolent diagnosis, this rare entity, with only two other cases identified, is important to consider in the clinician's differential diagnoses.


Keywords: Parosteal, lipoma, osseous lipoma, oral


How to cite this article:
Potter J, Richards C, Collin J. Parosteal lipoma of the mandible: A case report and review of the literature. J Oral Maxillofac Pathol 2022;26:129-30

How to cite this URL:
Potter J, Richards C, Collin J. Parosteal lipoma of the mandible: A case report and review of the literature. J Oral Maxillofac Pathol [serial online] 2022 [cited 2022 May 26];26:129-30. Available from: https://www.jomfp.in/text.asp?2022/26/1/129/341389





   Introduction Top


Lipomata are currently considered the most common benign soft-tissue mesenchymal neoplasm. As the main constituent of lipomata is mature adipose tissue, they appear most commonly in areas of the body where adipose tissue is present.[1] 15%–20% of lipomata are found in the head-and-neck region, most often the neck, with only 1%–5% of all lipomata within the oral cavity.[2] Lipomata account for only 0.1%–5% of all benign oral tumors.[3] Lipomata most frequently develop in patients over 40 years of age, more typically in men than women and usually with a slow progression over multiple years.[4],[5] Oral lipomata are most frequently detected in the lips, buccal mucosa, lingual and sublingual tissues.[1]

Clinically, lipomata tend to present as well-circumscribed masses, and those involving the oral cavity are frequently yellowish, soft and nontender. Histologically, the main constituent of lipomata is mature adipose tissue without evidence of nuclear or cellular atypia.[1],[6]

The case to be discussed is an osteolipoma with parosteal localization, also coined a parosteal lipoma. As far as our research can identify, this is the third case of a parosteal lipoma of the mandible documented in English-language literature, but it varies in its initial symptom presentation when compared with other reports of lipomata, osteolipoma and parosteal lipomata.


   Case Report Top


The patient was referred by his general medical practitioner to the Oral and Maxillofacial Surgery Department via an expedited suspected cancer pathway, for assessment of a lump of his right lower jaw noted by the patient 3 weeks prior. This lump had visibly enlarged over those few weeks and was becoming painful. The patient was also experiencing constitutional symptoms in this time period, with night sweats, fevers and chills. He had noted a slight facial asymmetry, but had no appetite, weight or skin changes, nor any sensory disturbance.

The patient's past medical history included hypogonadotropic hypogonadism primary lumbar microdiscectomy and gastroesophageal reflux disease. His regular medication included omeprazole, naproxen, testosterone injections and tramadol. The patient had no known allergies and had not smoked cigarettes for 10 years.

On examination, there was a 2 cm palpable bony hard mass fixed to the right mental protuberance, resulting in a subtle facial asymmetry. There was no associated tenderness, no overlying skin changes, sensory deficit or trismus. On intraoral examination, there was no palpable or visible buccal expansion of the labial sulcus, as this lump was positioned close to the inferior mandibular rim. No dental pathology was identified.


   Radiographic Examination Top


An orthopantomogram and a mandibular occlusal radiograph were taken at this first appointment to assess the composition and location of this bony mass and to identify any potential odontogenic source.

The mandibular true occlusal radiograph [Figure 1] demonstrates a calcified, slightly multilocular appearing lesion arising from the buccal cortex of the mandible in the right parasymphyseal region. The occlusal radiograph demonstrates the area as prominent with a mildly irregular periphery and lies adjacent to the lower right lateral incisor to first premolar. Although this lesion was not readily apparent on the panoramic radiograph, it did serve to help steer the differential diagnoses away from odontological causes [Figure 2]. Although features were not entirely consistent with a primary bone malignancy, an urgent biopsy was recommended by the radiologist.
Figure 1: The mixed radiopacity lesion rising from the buccal aspect of the right parasymphyseal region is evident on this mandibular true occlusal radiograph, with an ill-defined periphery

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Figure 2: Panoramic radiograph. No obvious odontogenic or bony pathology is noted

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Given the reported rapid progression of the lesion and constitutional symptoms, the working diagnosis was osteosarcoma. Other differential diagnoses at this time included exophytic bony lesions, such as exostosis, osteoma, osteochondroma and chondrosarcoma.[7]

A biopsy was conducted under local anesthetic, at this initial consultation appointment following radiographic investigation. An intraoral incision was made in the right labial vestibule, and the bony lump was evident subperiosteally, but free of the mandibular cortex. Due to well-circumscribed and encapsulated nature of lesion, the base of the lump was dissected easily from the surrounding tissue and excised whole. It did not appear attached to adjacent bone, but extended inferiorly, resting against and below the inferior border of the mandible. There was a small depression of mandibular cortex at the surgical site, suggesting a compression defect from this growth.[8]


   Histopathology Top


The hard tissue specimen measured 25 mm × 15 mm × 12 mm and was decalcified in formic acid. On microscopic examination, the lesion showed a relatively well-circumscribed polypoid structure, predominantly with mature adipose tissue and lobules of adipocytes. No significant cellular atypia, variation in cell size, nuclear atypia or conspicuous mitotic activity was identified. Islands of mature lamellar bone were scattered throughout the fatty tissue component. There are multiple foci of osseous metaplasia showing trabeculae of remodeling bone, focally incorporating loose fibrofatty tissue with no evidence of hematopoietic cells [Figure 3] and [Figure 4].
Figure 3: Low-power view photomicrograph demonstrating islands of mature lamellar bone scattered amongst the fatty tissue component

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Figure 4: High-power photomicrograph demonstrating mature adipose tissue and lobules of adipocytes

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The diagnosis agreed with the histopathologist was a benign adipocytic tumor of right mandibular parasymphysis, with a final differential diagnosis of either parosteal lipoma or lipoma with osseous metaplasia, to be correlated against the clinical picture. As this mass was firm and immobile on clinical examination, with evidence of cortical depression of the underlying mandible, coupled with the knowledge that parosteal lipomata often undergo osseous metaplasia, the diagnosis of parosteal lipoma was made.[8]

Plan for routine 6-month follow-up, but in the COVID-19 pandemic, face-to-face follow-up has been delayed.


   Discussion and Review of Literature Top


Lipomata have been separated into four forms by the World Health Organization 2002 guidelines, according to the origin of their location. These forms include: superficial lipoma (arises within subcutaneous tissue); deep lipoma (arises within deep soft tissue, deep to investing fascia), intramuscular or intermuscular lipoma (most commonly within large muscles of thigh, upper arm and shoulder) and parosteal lipoma (arise within the surface of bone, subperiosteally).[5],[9] Furthermore, when the lipoma is intimately related to or within bone, they are categorized in accordance with their relation to the parent bones, as intraosseous (within bone), cortical (relating to cortex of bone) or parosteal.[8] Parosteal lipomata are an uncommon type of lipoma and occur in intimate association with the periosteum of bone, mostly affect the long bones and presentation in the mandible is rare.[8] Only two other cases of parosteal lipomata of the oral cavity have been reported, both occurring in the mandible.[8],[10]

Osseous changes in lipomata are rare, seeming to occur in some longstanding and large lipomata. Titles, often used interchangeably, for lipomata with osseous components include: osteolipoma; lipoma with osseous metaplasia; osseous lipoma or ossifying lipoma. This subtype accounts for approximately 0.3% of all lipomata. Osteolipomata are found most frequently at the long bones but have been reported at the femur, radius, humerus, tibia, fibula, clavicle, pelvis and oral cavity.[2],[8]

Raghunath et al. conducted a review of English literature, identifying a total of 21 cases of osteolipomata of the head and neck, with only twelve cases of osteolipoma presenting in the oral cavity. Osteolipomata were found in the tongue, sublingual tissues, buccal vestibule, buccal mucosa, hard and soft palate and submandibular region.[2]

The parosteal lipomata exhibits relationship to the periosteum, with commonly an attachment to the periosteum, resulting in an osseous reaction occurring within the tumor. Parosteal lipomata may rest directly on the cortex, with or without cartilage or bone elements contained within the tumor.[2] Parosteal lipomata often lead to definite bony alterations of the parent bones, such as bony hyperostosis, protuberance erosion and compressive changes. Branch-like or linear cortical protuberances and ossification are frequently seen but aggressive bone destruction is consistently absent.[8] Parosteal lipomata usually present morphologically as homogenous, lobulated and often adherent to adjacent bone.[8]

Two main theories for the provenance of an osteolipoma include fibroblasts within the lipoma undergoing metaplasia into osteoblasts, a process which may be initiated by repetitive external microtrauma or ischemia secondary to outgrowth of the tumor's blood supply, leading to modification of the mesenchymal calls. The other theory is that the adipocytes and osseous components originate from a multipotent, undifferentiated mesenchymal stem cell.[1],[2],[8] Presentation of exophytic osseous components from the cortex of the mandible can highlight suspicions of osteochondroma, osteoma, osteosarcoma or chondrosarcoma. It is important to note that these tumors usually present without surrounding fat components. However, if spiculated periosteal new bone formation with an ill-defined border is present, one should consider osteosarcoma in their differentials.[8],[11],[12]

A literature review on the search engine PubMed and Google Scholar was conducted in 2020–2021, including search terms with Boolean operators for “oral” and “parosteal lipoma” or “lipoma with osseous metaplasia” or “ossifying lipoma” or “osseous lipoma.”


   Inclusion Criteria Top


  • Articles of English-language literature
  • Lipoma with osseous change or parosteal lipoma
  • Presentation of lipoma in the oral cavity.



   Exclusion Criteria Top


  • Osteolipomata presenting elsewhere on head and neck that didn't involve the oral cavity
  • Osteolipoma of the submandibular space detected by neck examination, without intraoral involvement
  • Osteolipoma with additional mesenchymal tissue evident, for example, osteochondrolipoma.
  • Insufficient information in report to confirm the lipoma meets the inclusion criteria.


The literature review identified two previous reports of parosteal localization of lipomata in the mandible and 22 cases of lipoma with osseous metaplasia within the oral cavity. This led to a total of 24 cases, which are detailed below.

[Table 1] displays the reported cases of oral osteolipomata chronologically, with inclusion of the date of publication, author, patient age in years (Y) and gender (M– Male, F– Female), presentation and location of the lesion, along with radiographic and histopathological findings. The two cases of parosteal lipomata are highlighted in green.
Table 1: Literature review using PubMed and Google Scholar searches and previous literature reviews for osteolipomata and parosteal lipoma of the oral cavity

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[Table 1] demonstrates that the average, mean age at which osteolipomata are detected is 46-years-old, with the duration of lesion being present for the average mean of 10.8 years. Only three out of the 26 cases presented with symptoms, including paresthesia from pressure of the mass and trismus. No other history of pain documented except for this current case. This review demonstrated a slight predilection of osteolipomata for female gender (52%). This is in contrast to existing literature, which have shown oral lipomata and osteolipomata to be more common in men.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27]

The treatment for lipomata, including parosteal and osseous lipomata, is surgical excision. It is not often difficult to dissect a lipoma contained within soft tissue, or a parosteal lipoma abutting the bone. If the lesion has an intimate osseous relationship, is fixed or has altered the parent bone form, surgical excision requires subperiosteal dissection, with potential for more invasive surgical procedures such as an osteotomy or segmental resection of bone, to free the mass from underlying bone. Local recurrence of these benign neoplasms is rare and malignant changes within parosteal lipomata have not been documented.[2],[8]


   Conclusions Top


Osteolipomata of the oral soft tissues are rare, particularly parosteal lipomata. The increasing cases in the literature should remind the clinician and pathologist to keep this entity in mind. Histopathological diagnosis according to the criteria mentioned in this review will help to categorize these rare lesions and further understand their origin. Despite their benign nature and lack of recurrence, it is essential to differentiate these entities from the malignant lesions, including osteosarcoma.[1]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgments

We would like to thank Dr. Miranda Pring, Consultant of Oral and Maxillofacial Pathology, for the histopathology.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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2.
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Castilho RM, Squarize CH, Nunes FD, Pinto Júnior DS. Osteolipoma: A rare lesion in the oral cavity. Br J Oral Maxillofac Surg 2004;42:363-4.  Back to cited text no. 4
    
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Upadhyaya JD, Cohen DM, Islam MN, Bhattacharyya I. Firm, dome-shaped mass of lower lip. Oral Surg Oral Med Oral Pathol Oral Radiol 2017;126:4-8.  Back to cited text no. 5
    
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Sun Z, Sun L, Zhang Z, Ma X. Ossifying parosteal lipoma of the mandible: A case report and review of the literature. Dentomaxillofac Radiol 2013;42:57852073.  Back to cited text no. 8
    
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Fletcher C, Unni K, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone. World Health Organisation Classification of Tumours. IARC Press, International Agency for Research on Cancer, Lyon. 2002.  Back to cited text no. 9
    
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Saghafi S, Mellati E, Sohrabi M. Osteolipoma of the oral and pharyngeal region; report of a case and review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e30-4.  Back to cited text no. 17
    
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Raviraj J, Kumar-Bokkasam V, Suresh D, Venkata S. Osteolipoma of buccal mucosa: Case report and literature review. J Clin Exp Dent 2016;8:e214-8.  Back to cited text no. 22
    
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Fukushima Y, Kitamura T, Hayashi N, Enoki Y, Sato T, Yoda T. A huge osteolipoma involving the coronoid process: A case report. J Oral Sci 2016;58:141-4.  Back to cited text no. 23
    
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