Atypical non-[99mTc]Tc-MIBI avid parathyroid adenoma with a sternal brown tumor, mimicking ectopic parathyroid adenoma in planar and SPECT images: Importance of SPECT/CT acquisition

Primary hyperparathyroidism (pHPT) is defined by the excess level of parathyroid hormone (PTH). Parathyroid adenoma is responsible for about 80% of all pHPT. Parathyroid adenoma with cystic feature and atypical pathology is recognized as a rare entity. Technetium-99m methoxy isobutyl isonitrile ([99mTc]Tc-MIBI) scintigraphy has favorable detection rate for ectopic gland as well as the brown tumors. SPECT/CT plays critical role in localizing abnormal tracer uptake. Herein, we report a severely hypercalcemic patient with cystic atypical parathyroid adenoma and mediastinal uptake, which was confined to a sternal lytic lesion (suggestive of brown tumor), which highlights the importance of SPECT/CT in [99mTc]Tc-MIBI imaging.