What is sternocleidomastoid tumor of infancy?

Also known as: fibromatosis colli of infancy, SMT, SCM.

The sternocleidomastoid is a neck muscle which joins the base of the skull to the collar bone. A sternocleidomastoid tumor of infancy is a rare, benign (non-malignant, non-cancerous or spreading) neck mass/lump (usually on the right side) that appears around the second and eighth week after birth, more often in boys, and often causing the baby’s head to be tilted to one side and be rotated to the other (torticollis -“twisted neck”).


Reviewed by: Jack Wolfsdorf, MD, FAAP

This page was last updated on: 1/29/2019 3:21:13 PM

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