A 5-week-old male infant, previously healthy, was admitted in the Emergency Department with a one-week right cervical swelling leading to restricted cervical movement. The clinical examination revealed a right cervical swelling of about 1 cm mobile that increased in size with muscle contraction.
A cervical ultrasound showed a fusiform thickening of the right sternocleidomastoid muscle (SCM) approximately 25 x 10 mm, consistent with Fibromatosis Colli. No cervical lymph nodes with pathological dimensions were identified. The infant had a significant improvement with a biweekly motor physiotherapy during 5 months.
Figure 1. Right lateral cervical tumefaction.
What criteria help differentiate Fibromatosis Colli from analogous neck masses in infants?