A Rare Case of Lipidized Fibrous Histiocytoma of the Oral Cavity

Abstract

Benign fibrous histiocytoma (FH) is a common cutaneous tumor that rarely occurs in the oral cavity. Lipidized FH is an uncommon variant characterized by abundant foam cells in collagenized stroma. To our knowledge, only a single case of oral lipidized FH affecting the tongue has been reported. We examine a case of lipidized FH in the buccal mucosa of a patient presenting with a gradually enlarging, pedunculated lesion measuring up to 26 mm. A histological examination revealed a well-marginated but unencapsulated tumor with a Grenz zone, hyalinized stroma, and central foam cell aggregation. Immunohistochemically, the spindle and foam cells were CD68-positive, with focal Factor XIIIa positivity and negative bcl-2 staining. The lesion was completely excised, and no recurrence was observed. To our knowledge, this is the second reported case of oral lipidized FH and the first case in the buccal mucosa. Given its rarity and histological overlap with other xanthomatous lesions, accurate diagnosis is crucial with immunohistochemistry. Complete excision appears to be curative; however, a long-term follow-up is recommended, considering the subtype of fibrous histiocytoma developing in the orofacial region.

Keywords: cd68; factor xiiia; foam cells; lipidized fibrous histiocytoma; oral cavity.

Figure 1. Macroscopic and histological findings

An exophytic tumor mass on the cheek (a) with a cut surface colored light tan and a yellowish area (arrows) in the center (b). Histologically, the pedunculated mass is entirely fibrous (c) with a subepithelial Grenz zone (double arrow) (d). Aggregation of foam cells (e) and scattered spindle cells with bland nuclei, and mature fat cells embedded in the collagenous stroma (f). The scale bars represent 5 mm (b and c), 1 mm (d), and 100 μm (e and f), respectively.

Figure 2. Immunohistochemical findings

Immunohistochemical analysis showed CD68 positivity in both spindle cells (a) and foam cells (b). Spindle cells were positive for Factor XIIIa (c), CD34 (d), and Rb (e), but negative for bcl-2 (f). Additionally, note the positive reactions of capillaries (arrows), endothelial cell nuclei (arrows), and lymphocytes (arrows) for CD34 (d), Rb (e), and bcl-2 (f), respectively. All scale bars represent 100 µm.