The term xanthoma, derived from the Greek word xanthos (meaning “yellow”), refers to a benign lesion characterized by the aggregation of lipid-containing histiocytes and foamy cells within tissues^1,2. Xanthomas typically represent a benign secondary manifestation of systemic diseases that affect lipid or glucose metabolism, such as dyslipidemia (type II or III hyperlipidemia) and diabetes^3,4. When a lesion occurs without such systemic conditions, it is called a primary xanthoma^5-7. Xanthomas usually present as a mass in soft or connective tissues, such as skin, subcutaneous tissue, tendons, or internal organs. Intraosseous xanthoma (IOX) is a rare form that can occur in the jaw bone. Since the first case was reported in 1964⁸, only around 50 cases in the jaw bone have been documented in the English literature, underscoring the rarity of this form of IOX.

To date, there has been only one reported case of orthognathic surgery performed on a mandible with an IOX that involved intraoral vertical ramus osteotomy⁹. However, in that case, osteotomy was performed, bypassing the lesion. This report describes a case in which sagittal split ramus osteotomy (SSRO) was performed directly at the ramus of a mandible with IOX without bypassing or avoiding the lesion.

A 23-year-old female patient visited the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, with a chief complaint of orthognathic surgery. Radiographic examinations, including posteroanterior (PA) cephalogram and panoramic radiographs taken at the first visit, revealed a slight radiolucency in the right ramus compared to the left side. The symptomless lesion was overlooked at the initial diagnosis due to its insignificant finding. The patient was then referred to the Department of Orthodontics, Seoul National University Dental Hospital for preoperative orthodontic treatment 1.5 years in duration. After completing the preoperative orthodontic phase, the patient was referred to the Department of Oral and Maxillofacial Surgery for orthognathic surgery.

The patient had no history of systemic disease such as dyslipidemia or diabetes. Preoperative blood tests confirmed normal cholesterol (177 mg/dL) and glucose (93 mg/dL) levels. Preoperative PA cephalogram and panoramic radiographs showed no significant differences from the initial radiographs. However, preoperative cone-beam computed tomography (CBCT) revealed a heterogeneous diffuse radiolucent-radiopaque lesion in the right ramus on the axial cut.(Fig. 1) Additionally, the cortical bone appeared generally thinner compared to the left ramus. The surgical plan was that orthognathic surgery would be performed along with simultaneous surgical removal of the intraosseous lesion.

Computer-assisted simulation surgery was performed using virtual surgical planning. The surgery was planned as a bimaxillary orthognathic procedure through a mandible-first approach, which the surgeon routinely performs. Horizontal osteotomy was performed above the lingula level after lingual flap elevation on the lingual side of the ramus using a low-speed handpiece with a small vulcanite bur and a long fissure bur. Sagittal osteotomy of the ramus and vertical osteotomy on the buccal side of the mandibular first molar area were done using a low-speed handpiece with a small fissure bur and a reciprocating saw. During the procedure, yellow-fat-like soft tissue was observed in the right ramus, where sagittal osteotomy was to be performed. Before sagittal osteotomy, the visible lesion was enucleated. After osteotomy, any remaining residual lesion was meticulously removed, along with a small amount of bone marrow.(Fig. 2) The enucleated soft tissue was sent to the Department of Oral Pathology for pathologic diagnosis. No abnormal findings were observed on the contralateral side (left ramus). Four-hole prefabricated miniplates were fixed on the proximal and distal segments of the osteotomized mandible. The maxilla was down fractured at the Le fort I osteotomy level, placed into the desired position according to the final occlusal splint, and fixed with L-shape miniplates (4 ea) and mini-screws (16 ea). The patient was discharged 4 days later without any complications and underwent suture removal after 2 weeks.

Histopathological examination confirmed a diagnosis of central xanthoma. Under the microscope, lipid-filled histiocytes and aggregates of foamy cells in scarce fibrous tissue were observed, along with isolated lymphocytes and plasma cells. Immunohistochemical staining showed positivity for CD68 and negativity for S-100 protein.(Fig. 3) During the follow-up period, the healing process was uneventful, and patterns of bony healing were noted on X-ray (PA cephalogram and panoramic view) and CBCT images taken 1 month and 6 months post-operative. At the one-year follow-up, X-ray (panoramic view and PA cephalogram) (Fig. 4) and multidetector computed tomography showed no significant interval changes in the lesion, with excellent bony union between segments.(Fig. 5) The patient reported no subjective discomfort. Titanium plates were removed from the maxilla and mandible under general anesthesia.

IOX are benign lesions characterized by the accumulation of lipid-laden, foamy macrophages. The pathogenesis of IOX stems from lipid leakage from nearby blood vessels, followed by phagocytosis of the lipids by macrophages^10-13. Since not all of the leaked lipids are degraded, the formation of lipid-laden, foamy macrophages ensues. It has also been proposed that these lesions originate as a degenerative or reparative form of other pre-existing lesions, such as simple bone cysts, fibrous dysplasia, and idiopathic bone cavities^5,7,14,15. Minor trauma has also been suggested as a contributing factor in the development of xanthoma^3,10. While xanthomas often manifest secondary to systemic conditions, primary xanthomas can develop independently of any underlying conditions. Among IOX, the occurrence of xanthomas in the jaw bone is extremely rare. To the best of our knowledge, 25 reports published in English-language journals between 1964 and 2024 described 59 cases of IOX of the jaw bone; they are summarized in Table 1.

The age of the patients ranged from 11 to 72 years, with an average age of 28.91 years and no sex predilection (52.5%, n=31 females and 45.7%, n=27 males). Of the 45 patients evaluated for systemic diseases, the majority did not have any systemic conditions (88.8%, n=40), while some exhibited hyperlipidemia (4.4%, n=2), vitamin D deficiency (2.2%, n=1), diabetes (2.2%, n=1), Noonan syndrome (2.2%, n=1), orofacial granulomatosis (2.2%, n=1). IOX of the jaw predominantly occurs in the mandible (91.5% n=54 mandible/8.5%, n=5 maxilla), with a particular predilection for the posterior part (77.7%, n=42 posterior mandible/9.2%, n=5 anterior mandible/7.4%, n=4 extending from anterior to the posterior mandible). Similar to the case presented in this report, many patients were free from symptoms, although swelling, pain, numbness, occlusion change, and tooth mobility or displacement can also occur (72.8%, n=43 asymptomatic/20.3%, n=12 swelling/8.4%, n=5 pain/1.6%, n=1 numbness/10.1%, n=6 occlusion change, tooth mobility, or displacement). Interestingly, of the five patients in whom IOX occurred in the maxilla, four exhibited symptoms. The radiographic appearance of IOX of the jaw bone varies widely. Although the majority of IOXs of the jaw show radiolucency with well-defined multilocular or unilocular margins, some lesions show a mixed or even radiopaque radiographic presentation and ill-defined margins². These various radiographic characteristics are not definitive features of IOX, which makes it difficult to diagnose by radiological imaging alone. These radiographic characteristics underscore the importance of thorough histopathological and immunohistochemical examination following the enucleation of suspicious lesions, which is essential to confirm the diagnosis and guide further management.

Histopathologically, IOX contains variable amounts of foamy histiocytes. Therefore, a diagnosis of IOX must be made after excluding all other histiocytic lesions^7,13. Histiocytic lesions can be classified into Langerhans cell-related and non-Langerhans lesions. IOX is a non-Langerhans lesion characterized by negativity for S-100 and CD1a immunofluorescence, which serves as a key trait differentiating Langerhans from non-Langerhans cell lesions^1,5. Although the differential diagnosis of IOX from benign fibrous histiocytoma and non-ossifying fibroma can be confusing, both non-IOX lesions show strong positivity for factor XIIIa immunohistochemical staining. They also feature spindle-shaped cells arranged in a storiform pattern, interspersed with multinucleated giant cells^7,12. The absence of fascicular fibrous stroma and odontogenic epithelial islands differentiates IOX from other xanthomatous lesions, such as granular cell odontogenic tumor².

Currently, there is yet to be complete consensus on optimal treatment of IOX of the jaw, curettage is widely accepted as the standard treatment². When complete curettage of the lesion was performed, no recurrence was observed. Even in cases where the lesion could not be completely excised due to patient factors or its large size, in most cases the lesions remained stable without any significant change or symptom aggravation^2,13. Saha et al.¹⁶ reported performing additional surgical intervention involving complete excision under general anesthesia after initial removal due to concerns about a more sinister pathology. In this second procedure, newly-formed woven bone was observed, and no remnants of the xanthoma were found. However, considering that the commonality among cases that recurred or progressed was incomplete removal of the lesion, it can be inferred that if part of the lesion remains, there is a risk of recurrence or progression of the lesion^1,9,17. This suggests that a single surgical intervention involving thorough curettage is needed and is sufficient for the removal of IOX from the jaw.

In this case, the patient presented with a desire for orthognathic surgery. The observation of yellow, fat-like soft tissue in the bone marrow during the surgical procedure raised suspicion of a possible xanthoma, which was later confirmed histologically as a central xanthoma. This diagnosis was substantiated by histopathological features consistent with previous cases, including the presence of lipid-filled histiocytes and foamy cells, along with positivity on immunohistochemical staining for CD68 and negativity for S100^2,13,18-26.

Post-operative radiographs demonstrated excellent bony union without signs of recurrence at the one-year follow-up, indicating that the surgical intervention was successful. The absence of differences in healing patterns between the left and right ramus is particularly noteworthy. This highlights the feasibility of performing SSRO directly through the IOX while maintaining close monitoring and appropriate histopathological evaluation. Although there have been only two reported cases of IOX removal via SSRO, including the one in this article, uneventful bony formation and healing at the operative site were observed in both cases¹⁰. This case underscores two key points in managing IOX of the jaw: (1) SSRO can be a useful approach for complete removal of lesions from the posterior mandible, (2) even if an unexpected IOX is encountered during orthognathic surgery, fixation of the proximal and distal segments of the mandible after complete curettage of the lesion may not affect the surgical outcome.

In summary, given its tendency to occur in the posterior part of the mandible, there is a possibility of encountering IOX during orthognathic surgery. Although the number of reported cases is limited and follow-up periods are relatively short, multiple sources suggest that complete curettage may be sufficient for removal of the lesion, which has a low recurrence rate. The successful outcome demonstrated in this case further supports the idea that IOXs encountered during orthognathic surgery, especially during SSRO, can be successfully treated with concurrent curettage of the lesion. Future studies are needed to explore the implications of IOX in the maxillofacial region, as well as long-term outcomes following surgical intervention, which will help to enhance our understanding of this rare lesion and improve treatment strategies.