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
malignant 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 (
Greek: ομφαλός), meaning
navel, and lithos (
Greek: λίθος), meaning
stone.[3]