Radiologic-Pathologic Conferences of The University of Texas M. D. Anderson Cancer Center

Abstract

1All authors: Division of Diagnostic Imaging, The University of Texas M. D. Anderson Cancer Center, Unit 1350, 1515 Holcombe Blvd., Houston, TX 77230. Address correspondence to G. J. Whitman. 26-year-old woman with a history of progressively worsening lower back pain for 1.5 years presented for evaluation. Physical examination was remarkable for mild swelling of the left flank, which was tender on palpation. Radiographs of the pelvis showed a large, lobulated, expansile eccentric lesion in the upper medial aspect of the left iliac bone. CT showed a 10-cm mass with destruction of the left iliac bone and the left side of the sacrum (Fig. 1A). MRI showed the mass to be hypointense to muscle on T1-weighted images and hyperintense to muscle on T2-weighted images (Fig. 1B). The mass showed enhancement on T1-weighted images obtained after the administration of IV gadolinium (Fig. 1C). The patient underwent surgical resection and the majority of the tumor was removed (Figs. 1D and 1E), with the remainder undergoing curettage. Gross pathology showed a multinodular, gray-silver to whitetan-pink, friable tumor. The final histopathologic diagnosis was chondromyxoid fibroma with an element of chondroblastoma. Chondromyxoid fibroma is a rare benign cartilaginous tumor, accounting for less than 1% of all primary bone tumors. Patients with chondromyxoid fibromas are usually in the second or third decade of life. The male to female ratio is reported to be 1.5:1. The tumor may be asymptomatic, and large lesions may cause pain, swelling, or distortion of bone. A study of 278 cases showed nearly half of the tumors in the long bones, and chondromyxoid fibroma has a predilection for occurring around the knee joint, especially in the proximal tibial metaphysis [1, 2]. Only five cases of chondromyxoid fibroma of the sacrum have been reported. A