Eccentric, mature osseous cap: A distinct imaging feature of sinonasal osteoblastoma

With the exception of osteomas, bone neoplasms that originate in the sinonasal cavity are seldom diagnosed on preoperative imaging due to a lack of characteristic radiographic features. Here we described the unusual occurrence of an osteoblastoma in the paranasal sinuses, and we drew focus to its salient imaging features. A highly unique imaging sign was indicated, and its pathologic basis was explained, with concurrent review of the literature.

Case series and review of the literature.

Two cases of sinonasal osteoblastoma were managed by definitive surgical resection. Both tumors on preoperative computed tomography demonstrated an expansile, heterogeneous fibro-osseous lesion with an eccentric, mature osseous cap. The dense osseous cap seen on imaging corresponded to a rim of mature bone on histopathology. A review of existing literature revealed the presence of this imaging sign in all reported cases.

Sinonasal osteoblastoma is an extremely rare entity with undefined imaging characteristics to guide preoperative decision-making. Here we reported, to our knowledge, the first description of a characteristic imaging sign of an eccentric, mature osseous cap, which corresponded histologically to a single peripheral layer rim of osteoblasts, a unique trait of osteoblastoma.