Congenital agenesis of right parotid gland confounds MIBG scan interpretation in craniocervical neuroblastoma.

A 10-month-old boy with left infraorbital temporal neuroblastoma presented for I-123 metaiodobenzylguanidine scan with SPECT/CT for staging. Symmetrical metaiodobenzylguanidine uptake in salivary glands is usually considered normal. In this case of right parotid agenesis, symmetrical uptake was misleading. Tumor in the right mandibular ramus masqueraded as normal parotid gland. Repeat imaging 3 months after chemotherapy revealed absence of physiologic right parotid gland activity. Correlation with CT from SPECT/CT demonstrated right parotid agenesis, confirmed on MRI. Few cases of unilateral parotid agenesis are reported in published literature. We also discuss the potential added value of higher-quality CT images in SPECT/CT tumor imaging.