A Posterior Neck Mass in a 7-Month-Old Infant

Abstract

A full-term, 7-month-old male infant presented to an outpatient pediatric otolaryngology clinic with a firm, irregularly shaped posterior neck mass. He had been diagnosed prenatally with cerebellar hypoplasia, so a magnetic resonance imaging study of the brain was performed at 1 month of age. This study demonstrated an incidental solid, homogenous mass in the subcutaneous fat of the right occiput with irregular borders and infiltration into the paraspinal musculature (Figure , A). On examination, the upper posterior neck mass was deep to palpation without overlying skin changes. The patient had no discomfort, and neck movement was not restricted.At 7 months of age, the patient underwent ultrasonography to assess interval change of the lesion, which confirmed a 3.4-cm × 1.6-cm × 3.7-cm mass that had grown proportionally with the patient and was relatively avascular. Shortly thereafter, the mass was excised en bloc along with a cuff of adjacent posterior neck muscle and subcutaneous tissue. Grossly, the lesion was firm, round, and white in color with a smooth intact border but no discrete capsule. Histologic examination revealed cells with oval nuclei and multiple small nucleoli surrounded by a pale eosinophilic and slightly fibrillary stroma (Figure, B and C). Immunohistochemical studies were diffusely positive for glial fibrillary acidic protein and vimentin, and focally positive for S100, NeuN, and synaptophysin.