Clinical features
- Generally present after birth (0,4% of births), during the second until the eight week of life
- Males more affected than females
- Often bilateral
- Associated with congenital anomalies-14%
- Associated with birth injury-50%
- In the lower third of the sternocleidomastoid
Fig 31a – Fibromatosis colli – Single fibroblasts, and regenerating multinucleated muscle fibres (H&E)
- Scant material
- Bland spindle fibroblasts, single or in clusters
- Absence of atypia
- fibromyxoid matrix
- Regenerating multinucleated muscle fibbers
Immunocytochemistry
- Vimentin: Positive
- Smooth muscle actin: Positive
Differential Diagnosis
- Fibrosarcoma
- Embryonal rhabdomyosarcoma
Main points
- Spontaneous regression in weeks to months
- Torticollis can be a complication
- Fine needle diagnosis highly recommended, since excision usually is not required