A 4-year-old boy presented with non-tender mass near the right lower molars. This had been incidentally noted by the kid's parents. The patient had no complaint of ache to the area. He was subsequently admitted to our hospital for further check. Laboratory blood examination of serum calcium, phosphorus, and parathormone levels was normal.
On physical examination, a smooth and non-tender mass was palpated in the right lower molars. The oral cavity checkup was not exceptional.
Computed tomography of the maxillofacial region showed a well-defined 25 mm x 16 mm osteolytic lesion affecting the right mandible; erosion of the cortex was present (Figure 1). The lesion was delicately excised using a piezosurgery and sent for frozen section that showed spindle cell, chronic inflammation, and macrophages. The gross specimen of the lesion showed whorled bundles of spindle-shaped fibroblasts (Figure 2), as well as foam cells, mingled with scant multinucleated giant cells, without any bone formation in the lesion. The lesion showed strongly and diffusely positive staining for SATB2 (Special AT-rich sequence binding protein 2) (Figure 3), focal positive for SMA (Anti-smooth muscle antibody), KP1 (Anti-CD 68 antibody), and ER (Estrogen Receptor) (Figure 4), and negative for H3.3G34W by immunohistochemistry. With respect to USP6 (Ubiquitin-specific proteases) break-apart fluorescence in situ hybridization, the result was negative (Figure 5). Whole exon sequencing for this lesion tested KRAS codon 12, codon 13, codon 61, and codon 146, which were all negative. The postoperative course was uneventful, the patient was followed for 15 months and continues to be asymptomatic.