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Musculoskeletal » Neck / Head
Fibromatosis Colli
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Presentation Eight-week old boy was found to have a palpable right sided neck mass by his mother. Doctor indicated ultrasound to rule out adenopathy.
Caption: Sagittal sonogram of the right neck.
Description: Sagittal sonogram shows that the mass is intramuscular, within the right sternocleidomastoid muscle.
Caption: Transverse sonogram of the right neck.
Description: Transverse sonogram shows that the mass is intramuscular, within the right sternocleidomastoid muscle.
Differential Diagnosis Fibromatosis Colli
Final Diagnosis Fibromatosis Colli
Fibromatosis colli is a rare form of infantile fibromatosis that occurs within the sternocleidomastoid muscle1. There may be a slight male predilection. It typically presents a few weeks after birth.
Presentation is usually with torticollis and is most frequently related to birth trauma (e.g. forceps delivery) or malposition (e.g. breech) in the womb. On clinical examination, there may be a growing, hard neck mass2.

The right sternocleidomastoid muscle is more commonly affected (73% of the time)3.

Ultrasound is the imaging modality of choice. 
The sternocleidomastoid muscle is diffusely enlarged (but most 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)4.

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 sonography1, smoothly blending with the unaffected fibres. 

A discrete mass should not be seen. 

The presence of hyperechoic calcific foci suggests previous haemorrhage5.

Case References
1. Patrick LE, O'shea P, Simoneaux SF et-al. Fibromatoses of childhood: the spectrum of radiographic findings. AJR Am J Roentgenol. 1996;166 (1): 163-9. AJR Am J Roentgenol (abstract) - Pubmed citation

2. Meuwly JY, Lepori D, Theumann N et-al. Multimodality imaging evaluation of the pediatric neck: techniques and spectrum of findings. Radiographics. 25 (4): 931-48. doi:10.1148/rg.254045142 - Pubmed citation

3. Crawford SC, Harnsberger HR, Johnson L et-al. Fibromatosis colli of infancy: CT and sonographic findings. AJR Am J Roentgenol. 1988;151 (6): 1183-4. AJR Am J Roentgenol (citation) - Pubmed citation

4. Robbin MR, Murphey MD, Temple HT et-al. Imaging of musculoskeletal fibromatosis. Radiographics. 21 (3): 585-600. Radiographics (full text) - Pubmed citation

5. Laffan EE, Ngan BY, Navarro OM. Pediatric soft-tissue tumors and pseudotumors: MR imaging features with pathologic correlation: part 2. Tumors of fibroblastic/myofibroblastic, so-called fibrohistiocytic, muscular, lymphomatous, neurogenic, hair matrix, and uncertain origin. Radiographics. 29 (4): e36. doi:10.1148/rg.e36 - Pubmed citation

6. Bansal AG, Oudsema R, Masseaux JA, Rosenberg HK. US of Pediatric Superficial Masses of the Head and Neck. (2018) Radiographics : a review publication of the Radiological Society of North America, Inc. 38 (4): 1239-1263. doi:10.1148/rg.2018170165 - Pubmed.

Technical Details
Ultrasound scanner. - Voluson 730 PRO. General Electric.
Transducer.- 10 - 12MHz linear array.
Scanning in both transverse and longitudinal planes.

Follow Up
It is a self-limiting condition and usually resolves within 4-8 months6 and requires no more than physiotherapy. 
We performed the annual control ultrasound, not showing any alteration in the sternocleidomastoid muscle. 

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