Enchondroma Protuberans of the Transverse Process of D8 Vertebra Extending to the 7th and 8th Ribs: A Rare Case Report

Background Enchondroma protuberans (EP) is rare, benign cartilaginous bone tumor arising from the intramedullary cavity of long bones and usually protrudes beyond the cortex with an exophytic growth pattern resembling osteochondroma. This study reports on a rare case of EP arising from the transverse process of the D8 vertebra and extending to the adjacent 7th and 8th ribs and the paraspinal tissues.

Methods A 45-year-old female patient came in with complaints of upper back pain radiating up to the left costal margin for the past 6 months. There were no parasthesias, and there was no history of any sensory or motor symptoms. On physical examination there was midline and left paraspinal tenderness over the D6 to D8 region. Anteroposterior and lateral X-ray images revealed a well-defined oval ossific mass lesion over the lateral aspect of the D8 vertebra, extending to the 7th and 8th ribs on the left side, and multiple bridging osteophytes were noted. Computed tomography scan showed an ossific mass lesion arising from the D8 transverse process with extension to the adjacent 7th and 8th ribs; its margins were well defined, with no periosteal reaction. Magnetic resonance imaging showed a well-defined expansile mass lesion arising from the transverse process of the D8 vertebra matrix; it was was isointense with adjacent marrow and had no evidence of calcifications or vascular flow voids and no encroachment into the spinal canal.

Results Complete resection of the mass lesion with the adjacent part of the 7th and 8th ribs and with intramedullary curettage was performed and sent for histopathologic examination. Histopathology showed bony trabeculae with normal mucosal elements, and a mild hypercellularity with binucleation. Chondrocytes in the myxoid matrix located in round lacunae were compatible with enchondroma, with no evidence of atypia. The postoperative period was uneventful, and after 12 months there were no signs of recurrence noted in computed tomography scan.

Conclusions EP is a rare presentation in the dorsal spine; it should be considered in the differential diagnosis of osteochondroma, enchondroma, chondrosarcoma, and periosteal chondroid tumors.