Extraosseous uptake of bone seeking
radiotracers can occur in lesions with calcification demonstrated histologically
or radiologically; or else in lesions with acute tissue necrosis, but without evidence
of calcification. Calcified meningiomas and cerebral infarction are examples of
these two categories. Radiotracer uptake in meningiomas is caused by three
known factors affecting calcium deposition (1):
- tumor calcification
- calvarial erosion
- formation of reactive bone
In this case, there is a small area of low
signal in the adjacent cavarium which likely represents the formation of
reactive bone, giving rise to focal increased radiotracer uptake. On MR, there is no evidence of tumoral calcification.
Unfortunately, a CT is not available at this time to confirm.
Meningiomas are common, and occasionally seen on bone scan. There are several published case reports of meningiomas incidentally picked up on bone scan, most commonly during the work-up for breast cancer (2, 3). The appearances on bone scan are non-specific, therefore cross sectional imaging (CT or MR) is necessary to further characterize these lesions.