Sternocleidomastoid tumor – rare infantile neck mass diagnosed by fine-needle aspiration cytology: Report of two cases

Sternocleidomastoid tumor, also known as fibromatosis colli, is a rare form of fibromatosis in infants which is a rare, benign, and self-limiting tumor of infancy presenting as a well-circumscribed, hard, immobile, and fusiform swelling in the lower or middle portion of the sternocleidomastoid muscle. Birth injury associated with difficult labor is the most favored hypothesis. We describe using two cases as an example how this condition can be diagnosed by careful clinical history taking and fine-needle aspiration cytology so to avoid the surgical intervention. Here, we highlighted the cytological features of the sternocleidomastoid tumor so that it can be easily differentiated from congenital, inflammatory, and neoplastic masses in the neck in an infant.