The small bump on this baby's temple/hairline was a dermoid cyst.
The dermoid cyst (DC) is composed of epithelium and appendageal elements and may contain bones, hair and teeth. See also median nasal dermoid fistula.
A round, subcutaneous, asymptomatic congenital nodule at the tail of the eyebrow, periorbitally, on the nose or scalp is characteristic. Most DCs are noted in the first 5 years of life. DCs generally grow slowly during the first few years of life and then remain almost unchanged thereafter. A pit or pore with hairs emanating from it may overly a dermoid cyst (see median nasal dermoid fistula).
Any midline nodule needs imaging to exclude other lesions, e.g. nasal glioma, thyroid remnant.
Any midline DC requires imaging studies to exclude dysraphism or intracranial or intraspinal extension or other diagnosis. A small, classic, asymptomatic DC on the lateral eyebrow/temple does not require immediate excision. It can be stable for years and as the child grows, it becomes less and less obvious and may "disappear". It need not be removed. However, some cysts continue to grow slowly and can even alter the shape of adjacent bone. Surgical removal may be done, usually by a pediatric surgeon or plastic surgeon.
See also the median nasal dermoid fistula.