Adamantinoma of Pelvis: A Rare Tumor at an Uncommon Site, with Diagnostic Implications

Adamantinoma is a low-grade malignant bone tumor with metastatic potential in the range of 15–20%, commonly affecting mid-diaphyseal tibial region and jaw. Numerous cases of adamantinoma affecting the appendicular skeleton have been reported but only three in the pelvis till date. We present the case of a 24-year-old male, who was initially reported as fibrous dysplasia for a lesion in pelvis. On review, a cellular tumor was noted, including areas resembling fibrous dysplasia, along with cords and nests of polygonal cells, which displayed positive immunoexpression with cytokeratin and p40. Subsequently, he underwent wide local resection (internal hemipelvectomy), along with mesh pseudoarthrosis was done. Diagnosis of adamantinoma was further confirmed, with clear resection margins. Currently, the patient is on a regular clinical and radiological follow-up. Careful assessment of key histomorphologic features, coupled with immunohistochemical stains and clinico-radiological correlation, is helpful in identifying this uncommon tumor at a rather rare site.