Presentation
This young child presents with a palpable, painless, right axillary, bony mass for investigation.
Patient Data
There is a solitary, large, exophytic, bone lesion arising from the right second rib, posterolateral aspect. It has medullary and cortical (outer and inner cortex) continuation with the rib. It measures 7.5 x 6.6 x 6.4 cm (anteroposterior x transverse x craniocaudal).There is remodeling of the rib. The lesion appears expansile with a thin peripheral cortex. It has lucent areas centrally, with multiple osseous septations and an irregular, nodular margin secondary to multiple sessile components. There is no associated abnormal soft tissue mass, no periosteal reaction and no cortical disruption or pathological fracture. Regional mass effect is present due to its expansive nature, with attenuation and bowing of the third and fourth ribs. There is no abnormal lesional or soft tissue enhancement.
The right subclavian artery is displaced mildly anteriorly by the large expansile osseous mass arising from the second rib. The right subclavian, axillary and brachial arteries are otherwise patent and normal.
The scapula, clavicle and rest of the ribs are intact and normal with no other similar bone lesion present.
The 3D and MIP images demonstrate the right 2nd rib osteochondromata. The regional right subclavian artery is minimally displaced anteriorly due to the expansile lesion. There is no enhancement of the lesion as expected. There is additionally no abnormal regional soft tissue swelling or enhancement to suggest aggressive/ neoplastic soft tissue involvement.
Photograph of the excised gross specimen showing cortical and medullary bone with a multinodular appearance suggesting multiple, sessile, osteochondromata.
Sections show a portion of the rib with several exophytic osteochondromata, one of which can be seen in the above microphotograph. These show evidence of a proliferation of cartilage capped exostosis with no significant atypia, mitotic activity or necrosis/thickening to suggest malignancy.
Case Discussion
Features suggestive of histopathologically proven, multiple, benign, sessile, osteochondromata of the right second rib appearing as a large, solitary, osseous, mass lesion. There is well demonstrated cortical and medullary bone continuation on CT imaging with no aggressive features to suggest malignant transformation. Specifically, there is no pathological fracture, no cortical disruption, no soft tissue component and no abnormal enhancement.
CT chest and angiogram were requested to delineate regional arterial and venous anatomy for preoperative planning and additionally to exclude potential complications of the large mass.
The lesion was completely excised with clear surgical margins and the patient had an uneventful post-operative period.
Case courtesy of Dr S. Palliam.