Omphalolith

An omphalolith, also known as a umbolith, omphalith,^[1] navel stone,^[2] or umbilical concretion^[3] is a periumbilical mass that may form due to the accumulation of sebum and keratin.^[4] The colour is black or brown, and may be related to the skin type of the patient.^[2] It may resemble a melanoma.^{[5][page needed]} It may be caused by poor hygiene,^[6]: 121 and may form in retracted navels in obese people.^[3]

Etymology

The name was derived from the Greek words omphalos (ομφαλός) 'navel' and lithos (λίθος) 'stone'.^[3]