Intraosseous pilomatricoma: a possible rare skeletal manifestation of Gardner syndrome.

Here we report a case of intraosseous pilomatricoma in a patient with Gardner syndrome. A 17-year-old boy with a family history of Gardner syndrome and multiple cutaneous epidermoid cysts presented with pain in the region below the knee of the left leg. Plain radiographs displayed a well-circumscribed eccentric lesion of mixed radiolucent and radiopaque density within the diaphysis of the left proximal tibia. By magnetic resonance (MR) imaging, the lesion appeared as a low intensity lesion in T1-weighted images and a heterogeneous high intensity lesion with a low-signal radiation pattern on T2-weighted images. Gadolinium enhancement was observed partially within the lesion and intensely in the lesion rim. After curettage, histological examination revealed a massive accumulation of keratinous material with epithelial nests that displayed both epidermal and trichilemmal keratinization with basaloid and shadow cells and with metaplastic ossification. These features confirmed a pathological diagnosis of intraosseous counterpart of pilomatricoma. In the context of this patient's skin lesions, intraosseous pilomatricoma may be a rare skeletal manifestation of Gardner syndrome.