Presentation
Pain following fall.
Patient Data
Mildly comminuted fracture of the humerus is seen at the junction of the proximal and middle thirds of the diaphysis. The cortex in this region is thinned with the impression of an expansile medullary lesion. The medulla had a somewhat permeated appearance with a broad zone of transition. No definite periosteal reaction can be identified. Humeral head is rotated, however the shoulder joint is enlocated.
Pathological transverse comminuted fracture of the mid to distal diaphysis of the humerus is noted with surrounding edema. The fracture passes through a central intramedullary lesion that measures approximately 7.5cm craniocaudally which occupies most of the cross sectional diameter of the humerus with slight expansion of the bone and thinning of the cortex. Margins are well defined with a narrow zone of transition, without bony edema proximal or distal. The lesion is high T2 signal with speckled areas of low T2 signal - I note on the X-ray the lesion shows flecks of calcification in a rings / arcs pattern. No gross associated soft tissue mass. Enhancement is noted in the lesion.
Impression:
Pathological fracture of the right humerus through a solitary intramedullary lesion. X-ray is usually more specific than MRI in this setting, but the overall impression is of a low grade chondroid lesion (enchondroma or low grade chondrosarcoma). Further assessment is difficult given the pathological fracture.
Case Discussion
The patient went on to have a biopsy at the time of surgery.
Histology
MICROSCOPIC DESCRIPTION: The sections show a mildly cellular cartilaginous tumor. It forms lobules and nests. No prominent myxoid change is seen. The tumor is seen in the medulla. The rounded nests are surrounded by lamellar bone and mineralized matrix. There is no breach of the bone into the soft tissue. The chondrocytes show no significant nuclear atypia. Rare binucleated forms are seen. No abnormal mitoses are identified. There is no necrosis. At the fracture site, there is enchondral ossification with new bone formation and adjacent granulation tissue. The features are those of enchondroma. There is no evidence of malignancy.
DIAGNOSIS: Enchondroma.
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