123I-Metaiodobenzylguanidine uptake in the nape of the neck of children: likely visualization of brown adipose tissue.

UNLABELLED: The distribution of radioiodinated metaiodobenzylguanidine (MIBG) has been studied primarily in patients with neuroendocrine tumors-in pediatrics, particularly with neuroblastomas. Sometimes, symmetric accumulation in which no tumor is identified is seen in the nape-of-the-neck region. We estimated visually whether accumulation was found in the nape of the neck and studied the characteristics of the accumulation. METHODS: Retrospectively, we investigated 266 (123)I-MIBG scintigraphic studies performed on pediatric patients who had been treated for neuroendocrine tumors or who were suspected of having such tumors. RESULTS: Accumulation in the nape of the neck was seen in 32 of 266 studies (12%); in none of these cases was the accumulation identified as a tumor by other imaging modalities or follow-up studies. In the same individuals, the accumulation varied and it was observed more often during winter. CONCLUSION: Symmetric (123)I-MIBG accumulations in the nape-of-the-neck region observed in children are thought to be related to the uptake in brown adipose tissue.