Periosteal Chondroma of the Pelvis: An Uncommon Tumor in an Unusual Location.

Periosteal chondromas (PCs) are rare tumors composed of hyaline cartilage that are typically present in long bones and tubular bones of the hand. These lesions are easily mistaken for other, more common tumors. This study reports a case of PC located in the posterior pelvis of a 24-year-old female. The patient initially presented with a four-month history of pelvic pain with a presumptive diagnosis of endometriosis. However, when an MRI was performed, a 6.0 cm x 5.6 cm x 4.5 cm mass was found along the right posterior ilium extending to the ipsilateral sacroiliac joint. The patient underwent intralesional excision and curettage of the mass. Histologic analysis of the excised lesion revealed a proliferation of chondrocytes and abundant hyaline cartilage without chondroblasts, further suggesting the diagnosis of PC. The current study highlights the unusual location of this rare tumor and alerts the physician of the clinical presentation and differential diagnosis.