Introduction
Although lipoma (a benign soft tissue neoplasm) is common generally, it has a very low rate of incidence in the oral and pharyngeal region. Lipoma has numbers of variants: angio-lipoma, fibrolipoma, chondrolipoma, osteolipoma/chondrolipoma, adenolipoma, perineural lipoma, and myxoid lipoma [1,2]. Fibrolipoma (FL) is a histological subtype of lipoma that can be identified by a fibrous component that is mixed with adipose tissue lobules. Its consistency depends on the amount and distribution of fibrous tissue and the tumor depth. It may vary from soft to firm. The etiopathogeneses of lipoma and fibrolipoma remain unknown, but there are three possible reasons for the appearance of these lesions: it can be a congenital lesion due to the lack of endocrinal balance, which can arise with degeneration of a fibromatous tumor, or maturation of lipoblastomatosis. Moreover, mild trauma may cause adipose tissue proliferation; also, fibrolipoma can form beneath a complete denture. Magnetic resonance imaging (MRI) may be useful to diagnose the types of oral cavity lesions that are raised from adipose tissue. In general, lipoma displays high signal intensity and appears to be well-encapsulated masses on both T1- and T2-weighted images. Immunohistochemically can help to diagnose fibrolipoma by evaluating the expression rate of proliferating cell nuclear antigen (PCNA) and Ki-67. The expression of Ki-67 expression may indicate malignancy or recurrence. Fibrolipoma can show higher Ki-67 expression than classical lipoma and other variants of lipoma. Surgical excision must be operated to treat fibrolipoma. The prognosis of this type of lesion is generally favorable; if the surgery is performed well, it is not likely for this lesion to return. A follow-up must be considered. It can appear in all ages; although, it is mostly diagnosed in 40-60 years old patients. These lesions have a mean diameter of 2 centimeters (cm) in the oral cavity.
The lipoma of the mouth was described by Roux in 1848 as “yellow epulis” firstly. Among all benign oral lesions, oral lipoma has an incidence rate of about 1–4% and a prevalence rate of approximately 0.0002%. The review of English literature demonstrated a variable distribution of oral lipomas; however, about 50% of them were on the buccal mucosa. Other 50% of the oral lipomas were diagnosed in the tongue, floor of the mouth, lips, palate, and gingiva [1,2]. FL is a highly uncommon variation of lipoma and contains about 1.6% of all facial lipomas [3]. FL of the oral cavity has been infrequently reported. To the best of our knowledge, the review of the literature revealed a total of 33 cases of intraoral FL till now (Figure 1) [4].
As this lesion does not have any pain and grows slowly in the oral cavity, it is hard to clinically evaluate its true incidence rate. Patients report the lesion to the dentist only when it turns symptomatic, for esthetics, or oral function.
Different studies were explaining their cases due to their rarity: Pereira reported a rare histologic variant of FL on the lingual marginal gingiva of the mandibular left third molar of a 35-year-old female patient in 2014 in India. Iaconetta also reported a rare FL of the tongue on the ventral surface of the tongue of a 71-year-old female patient in 2015 in Italy. Furthermore, Castellani reported a rare case of intraosseous fibrolipoma of the mandible in a 25-year-old female patient in 2015 in Italy. All these three cases were important to be reported because of the rareness of FL in the oral cavity and the site of FL in each of these presented cases.
As mentioned above, FL in the oral cavity is a rare case. In this paper, a case of gingival FL will be analyzed and its clinic and pathological features along with the patient management and follow-up will be discussed.