Presentation
Left hand progressive swelling for 3 years.
Patient Data
Expansile lytic bone lesion is seen replacing the fourth metacarpal bone. The base of the fourth metacarpal bone is partially preserved. The metacarpal cortex is markedly thinned out, but still preserved. Tiny septations seen within the lesion. Scalloping of the lateral cortex of the 5th metacarpal bone is seen. Aneurysmal bone cyst is on the top of the differential diagnosis.
MRI study shows an expansile bony lesion replacing the fourth left metacarpal bone containing multiple internal septations and peripheral soft tissue component best seen on the distal aspect of the lesion. The soft tissue component appears intermediate low on T2 and T1 with intense enhancement on the post contrast images. The lesion has multiple fluid-fluid levels on T2 with areas of low T2.
Case Discussion
This case shows the typical radiographic appearance of aneurysmal bone cyst. While the appearance on MRI T2 weighted image is consistent with aneurysmal bone cyst, the presence of an enhancing soft tissue component suggests a coexisting lesion. One third of aneurysmal bone cysts are actually secondary to bone lesion like giant cell tumor or chondroblastoma. The patient underwent curettage/debulking of lesion and bone grafting was done. The histopathology result:
"LEFT METACARPAL:
CONSISTENT WITH GIANT CELL TUMOR WITH SECONDARY ANEURYSMAL BONE CYST."
The patient was followed up for long period with no evidence of recurrence.
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