Spindle cell lipoma of the tongue: First case report from the Gulf region and review of the literature

Key Clinical Message Spindle cell lipoma is a histological variant of oral lipomas. In this report, we present the first case from the Gulf region with the most comprehensive literature review. Clinicians should consider rare tumors in the differential diagnoses of oral masses.


| INTRODUCTION
Lipomas are prevalent benign soft tissue neoplasms of mesenchymal origin that develop in up to 20% of cases in the head and neck area. 1 Oral lipoma is considered to account for 1% to 4% of all benign mouth lesions. 2 Pleomorphic lipoma, angiolipoma, chondrolipoma, fibrolipoma, and spindle cell lipoma (SCL) are all histologic variations. 15Enzinger and Harvey were the first to report the SCL variant in 1975; morphologically, this variant has mature adipose tissue with bland spindle cells, myxoid stroma, ropey collagen bundles, and dispersed mast cells. 3,15It was initially identified outside the oral cavity and tongue, and it remains an uncommon phenomenon across both locations. 7An asymptomatic, confined lump was the most common presenting complaint. 2However, tumors with equivalent form and odd presentations are becoming more frequent, rendering accurate diagnosis even more crucial. 12To be managed effectively, SCL must be pathologically distinguished from liposarcoma, other spindle cell neoplasms, and myxoid lesions. 4,5Cytology, histology, immunohistochemistry, and cytogenetics, together with clinical presentation, are essential for determining the proper diagnosis of SCL. 4,5The preferred therapy is surgical excision, which includes convenient removal from surrounding tissues. 5Lingual SCL has a benign clinical course with little chance of recurrence, although long-term monitoring is required. 29The significance of this paper is to report a case of SCL in the tongue, shed some light on previously reported literature that is relatively sparse and portray the clinicopathological aspects of this unusual kind of oral Lipoma.The review of literature in our article entailed the search of PubMed as a primary database source to seek all published case reports in the available scientific literature.The key terms used were "Spindle Cell Lipoma" AND "Tongue Lesion" OR "Spindle Cell Tumor" AND "Lipoma of the Tongue."All articles in the English language were included in our search.Certain variables such as demographic data, location of the tumor, diagnosis, treatment plans, and follow-up were recorded and detailed in our results (Table 1).

| CASE PRESENTATION
A 33-year-old Saudi female presented to the general surgery clinic complaining of a swelling on the anterior aspect of the tongue.The mass was freely mobile with no impaired tongue mobility.She did not report any pain, dysphagia, dysphonia, dysgeusia, bleeding, dysarthria, or dyspnea.The mass was slowly growing over the course of several months.The patient denied having any other constitutional symptoms.Past medical and family history were both unremarkable.The rest of her history was noncontributory.
On physical examination, the patient's temperature was 37.3°C, blood pressure 121/84 mm Hg, and pulse 84 bpm with an SpO2 of 96% on room air.An approximately 20 × 10 mm submucosal soft, rubbery, and freely mobile mass over the anterior surface of the tongue was identified.Otherwise, the overlying mucosa was intact, the cervical lymph nodes were nonpalpable, and no other abnormalities were detected in the oral cavity.The patient is fit with BMI of 24.2 kg/m 2 .A provisional diagnosis of large tongue papilloma that is 30 mm in size was made.
Subsequently, she was scheduled for excisional biopsy and a series of laboratory tests were ordered.Beginning with a complete blood count (CBC), all parameters were within normal limits except for MCHC, which revealed a slight elevation of 34.70 g/dL.Additionally, further laboratory tests ordered included basic metabolic panel (BMP) whose components were all within reference range.The patient's blood group is O+ and negative for antibodies.Coagulation profile was also normal.Lastly, anti-HCV, HBsAg, and HIV Ag/Ab were all found to be nonreactive.
The patient underwent excisional biopsy under general anesthesia.The tumor was a polypoidal piece of grayish-yellowish tissue measuring 15 × 10 mm.It was well-encapsulated and excised in one cassette as shown in Figure 1.The patient was discharged on the same day without any postoperative complications with homecare instructions on Cefuroxime 500 mg PO (Oral) Tablet OD (Once Daily) for 14 days, Diclofenac Sodium 75 mg PO Capsule OD for 20 days, Miconazole 2% Oral Gel, Avalon (Azithromycin), and Povidone Iodine 10% Mouth Wash 135 mL.Postoperative follow-up was uneventful, and the patient did not have any complaints regarding mastication or speech.
The histopathological findings revealed a marginally excised lipomatous tumor containing a mixture of adipocytes, bland spindle cells, and rubbery collagen fiber, consistent with SCL.Additionally, immunohistochemistry was positive for CD34 and absent for retinoblastoma 1 (Rb1).Other differentials such as well-differentiated liposarcoma and lipoblastoma were excluded.

| DISCUSSION
Lipomas are the most common soft tissue mesenchymal tumors. 15,31The World Health Organization (WHO) classifies lipomatous tumors into several types-conventional lipoma, fibrolipoma, angiolipoma, spindle cell/pleomorphic lipoma, myxolipoma, chondroid lipoma, osteolipoma, myolipoma, lipomatosis, nerve lipomatosis, lipoblastoma/ lipoblastomatosis, and hibernoma. 32Although lipomas are the most common mesenchymal tumors of soft tissue, they are rare in the oral region, accounting for no more than 2.2-4.4% of intraoral tumors. 15,31The exact proportion of SCL among intraoral lipomas is a subject of controversy, as it has been suggested that SCL make up anywhere from 0 to 9.8% among intraoral lipoma cases. 24However, the largest study to date by Furlong et al. 15 which analyzed 125 cases of lipomas in the oral and maxillofacial region, found SCL representing 59 (47%) of the cases.
The clinical presentations of lipomas are variable, with the most common picture being of slow-growing painless masses that do not impair tongue mobility. 21However, some patients may present with a range of other symptoms, including dysphagia, dysphonia, dysgeusia, bleeding, or difficulty breathing and articulating speech. 25,26he diagnosis of SCL of the tongue is usually based on histopathological examination, which reveals intersecting fascicles of bland spindle-shaped cells and mature     adipocytes, interspersed myxoid stroma, dispersed mast cells, and eosinophilic ropey collagen bundles. 3,15Spindle cell lipoma and pleomorphic lipoma are currently considered by WHO 32 to be the same entity, only differing by the presence of floret-like or atypical stromal giant cells. 25,33mmunohistochemical studies can also aid in the diagnosis of SCLs, although the marker like CD34 positivity, is not specific to SCL and can be commonly seen in several other lipomatous and nonlipomatous soft tissue tumors. 10Typical SCLs show CD34-positive cells; S-100 protein-positive adipocytes; S-100 protein-negative spindle cells; and MDM2, desmin, smooth muscle actin, CDK4-negative cells. 25,30,34Differential diagnoses for SCL include lipoma with fibrosis, fibrolipoma, pleomorphic lipoma, atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDLPS), and solitary fibrous tumors (SFTs). 23,30pon reviewing 43 cases of SCLs of the tongue, we found that almost all the patients (except for one case by Shrestha et al. 29 ) were adults, with an age range of 7-86 years, with a mean age of 61 years and median age of 64.5 years.Our case was for a 33-year-old female, which is the third youngest case reported and well below the reported median age.Our case revealed a male: female ratio of 1.57:1, which is in accordance with the reported male: female ratio ranging from 1.19:1 to 2.75:1. 15,35Of note, our case reported no significant comorbidities or risk factors for the development of lipomas.The most common clinical presentation reported (24/30) was "painless mass" with only 2/30 cases presenting with painful masses. 13,25n addition, 3/30 cases reported eating or speech difficulties. 19,21,29Of note, one case reported by Lau et al. 25 presented as an incidental finding during another oral procedure.Our case similarly presented as a slowly growing painless mass over months.
While our case presented as an anterior lesion, the location of lingual SCL lesions reported in the literature varied between left border 12/27, right border 8/27, bilateral 3/27, midline 2/27, and ventral 1/27.The largest diameters of the SCL lesions reported in the literature ranged between 2 and 42 mm with a median of 12.5 mm and mean of 15.35 mm.Our patient presented with a mass measuring 30 mm in its largest diameter, which is relatively large compared with previously reported cases.Diagnosis in our case was established by histopathology and immunohistochemistry; however, cytogenetic studies were not done.Of note, two reported cases used fine-needle aspiration (FNA) as part of their work-up, which has shown considerable diagnostic efficacy. 8,12In addition, five cases reported using additional diagnostic imaging (magnetic resonance imaging and ultrasound). 14,21,27,30eported cases relied on histopathologic examination and immunohistochemistry as a gold standard for diagnosis.While Mandahl et al. 36 revealed a role for 16q13-qter and 13q deletions in extra-oral SCL/PL, none of the reviewed cases incorporated cytogenetic studies in their work-up, and thus, the presence of this cytogenetic profile in lingual SCL cannot be ascertained.
All cases reported, as well as our case, were definitively treated with local excision.No operative complications or recurrences have been reported so far for lingual SCL, while one case of recurrence was reported by Fletcher et al. 37 for extra-oral SCL lesions.Follow-up in reported cases ranged from 6 to 118 months, with a median follow-up of 22 months and mean of 33.6 months.The ideal follow-up duration and frequency remain largely unknown for lingual and generally oral SCL and merit future studies.
This study highlights that despite lingual SCL being initially considered a rare subtype of tongue neoplasm, there is an increasing number of reported lingual SCL cases among patients presenting with tongue masses.This emphasizes the relevance of accurate diagnosis of tongue lesions, whether by cytology, imaging, histopathology, immunohistochemistry, or cytogenetics as there is considerable diagnostic overlap among lipomatous and nonlipomatous pathologies of the tongue.In addition, the ideal follow-up duration and frequency should be identified to minimize recurrences while ensuring patients' comfort.
Our study has certain limitations.First, conclusions from our literature review are limited as our review is derived from case reports rather than case-control, cohort studies, or experimental studies.Second, despite careful searches, we have probably not included all reported cases of lingual SCL.However, our review is the most complete review of all published lingual SCL cases to date.

| CONCLUSION
To our knowledge, this is the first case of reported lingual SCL in the Gulf region.Our patient, a middle-aged woman presented with a painless anterior tongue mass and was subsequently diagnosed with lingual SCL, a relatively rare tongue tumor despite her having no predisposing risk factors.Our literature review of 43 cases of SCL of the tongue highlights their variable presentation, the role of different diagnostic modalities (cytology, imaging, histopathology, immunohistochemistry, or cytogenetics), their relatively good outcomes, and their low risk of recurrence.Surgical excision remains the mainstay of treatment for these tumors.Overall, our case adds to the limited body of literature surrounding this rare tumor and emphasizes the importance of considering rare tumors in the differential diagnosis of oral masses.

T A B L E 1
Summary of all previously reported cases of spindle cell lipomas (SCL) of the tongue.

F I G U R E 1
Histopathology of the resected specimen denoting (A) Spindle cell lipoma containing a mixture of adipocytes, bland spindle cells, and rubbery collagen fiber.(B) Benign adipocytic neoplasm showed muscle at the periphery.(C) Low power view of benign adipocytic neoplasm with bland spindle cells.