Imaging description

A one-month-old male presented with a palpable right neck mass, which had been noticed 10 days previously. The mass was not perceived to be painful or bothersome to the patient. There was no reported fever or weight loss. He was feeding normally and there was ipsilateral mild torticollis. He was born at 37 weeks by cesarean section due to cardiac decelerations during labor. Imaging evaluation with ultrasound (US) (Fig. 2.1a) demonstrated heterogeneous, mass-like enlargement involving the right inferior sternocleidomastoid muscle (SCM). The mass tapered gently toward the SCM and was surrounded by normal appearing SCM. The fascial planes surrounding the muscle were preserved. There were morphologically normal appearing prominent ipsilateral cervical chain lymph nodes. The lesion did demonstrate moderate internal vascularity on Doppler ultrasound (Fig. 2.1b).

An MRI was also performed in spite of the fact that the US appearance was strongly suggestive of fibromatosis colli. This demonstrated enlargement of the inferior right SCM, with intact surrounding fascial planes. The process was confined to the inferior SCM. There was increased T2 signal and heterogeneous enhancement of the involved muscle (Fig. 2.1c, d, e). There were no calcifications present in the lesion. The MRI findings also supported the diagnosis of fibromatosis colli.