Healthy 12 month boy had an asymptomatic congenital nodule on his nose. The nodule was mobile, nontender, and had changed little since birth. What is the most likely diagnosis ?
Ans : Sequestration Dermoid Cyst Discussion - a dermoid cyst lies deep to the skin and is lined by skin and all types contains desqumated putaceous material which are derived form the desqumated cells. 4 types of dermod cyst a) Sequestration dermoid - formed congenitally due to inclusion of epithelium, buried at the line of fusion between 2 embryonic segments. May contain hair, sweat glands, sebaceous glands or just plain squamous epithelium common sites - at the midline of the body ex. neck, root of nose - external angular - just above the outer canthus of the eye ( at the line of fusion of fronto-nasal and maxillary process ) - post auricular - at the site of fusion of mesodermal hillocks - at the site of fusion of skull bones b) Implantation dermoid - it's an acquired dermoid and arises from indriven epithelium beneath the skin due to a puncture injury eg. needle prick or thorn prick. common in gardeners and tailors and in surgical practice - if we fail to evert the skin edges along suture lines. Note - an implantation dermoid may have an overlying scar as opposed to no scar in sequestration dermoid and a punctum in sebaceous cyst. c) Tubulo dermoid - develops from an unobliterated portion of a congenital epidermal duct. ex - thyroglossal cyst ( commonest example ) d) teratomatous dermoid - develops from totipotent cells with ectodermal predominance and contains mesodermal elements like bone, cartilage etc. ex - ovarian teratoma Credit to everybody for recognising the very subtle dermoid (Y)
