False-Positive 123I-MIBG Uptake Attributable to Contralateral Erector Spinae Muscle Hypertrophy Following Retroperitoneal Surgery in a Child With Neuroblastoma.
Keyu Zhang, Fang Wang, Bingyan Zhang et al.
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Case in brief
A 5-year-old girl with high-risk neuroblastoma underwent ¹²³I-MIBG SPECT/CT after resection of a right adrenal tumor; baseline imaging showed no abnormal uptake. At 6 months, imaging demonstrated focal uptake in the left erector spinae muscle, corresponding to muscle hypertrophy on CT. At 12 months, the uptake had resolved completely, while the hypertrophy had only partially regressed. The imaging finding was therefore interpreted as transient false-positive uptake associated with the hypertrophied muscle rather than persistent tumor-related uptake.
What made this case unusual
The focal uptake occurred in the contralateral erector spinae muscle after asymmetric retroperitoneal surgery and resolved despite residual muscle hypertrophy.
Diagnostic / clinical pearl
When unexpected focal ¹²³I-MIBG uptake is seen after asymmetric surgery, correlate it with CT findings; hypertrophied skeletal muscle can produce transient uptake that mimics disease.