Fibromatosis colli

Last revised by Satish Kumar Gupta on 3 Aug 2023

Fibromatosis colli is a rare form of infantile fibromatosis that occurs within the sternocleidomastoid muscle.

Fibromatosis colli typically presents a few weeks after birth. There may be a slight male predilection.

Infants present with swelling in the neck and/or torticollis. It is unilateral in most cases. On clinical examination, there may be a growing, hard neck mass 7.

Fibromatosis colli is thought to be related to birth trauma (e.g. forceps delivery and difficult labor) or malposition (e.g. breech) in the womb. Resulting hemorrhage eventually results in fibrosis.  

The importance of fibromatosis colli, above all else, is that it must be recognized for its benign nature.

The right sternocleidomastoid muscle is more commonly affected (73% of the time).

Ultrasound is the imaging modality of choice. The sternocleidomastoid muscle is diffusely enlarged (but mostly involves the muscle belly) to assume a fusiform/ellipsoid shape/thickening with resultant shortening, therefore the chin is turned away from the affected side (the mastoid process is drawn inferiorly towards the ipsilateral head of clavicle). Echogenicity may vary in the affected fibrotic regions. Spectral Doppler interrogation may reveal a high resistance waveform. The enlarged area often moves synchronously with the rest of the sternocleidomastoid on real-time sonography 1, smoothly blending with the unaffected fibers. A discrete mass should not be seen. The presence of hyperechoic calcific foci suggests previous hemorrhage.

Typically shows a diffusely enlarged sternocleidomastoid that is isoattenuating to normal neighboring musculature. Adjacent fat planes are well preserved. At times, calcification may be present 2.

It is a self-limiting condition and usually resolves within 4-8 months 3 and mostly requires nothing more than physiotherapy in form of active and passive stretching exercises.

For a general differential see: differential diagnosis of pediatric cervical lesions.

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