Discussion:
Omphalolith or umbilical concretion is a rare and benign affection due to the accumulation of sebum and keratin in the umbilicus (2,3). It usually presents as a firm black mass. The pigmented color of the majority of omphaloliths is explained by melanin accumulation and lipid oxidation (4).
Omphalolith mainly affects elderly women with deep and narrow umbilicus and poor corporal hygiene (5). Obesity is another predisposing factor (5,6). In the first case, a deep and retracted umbilicus associated with insufficient hygiene led to the formation of the omphalolith in a young and non-obese female patient. Having Wilson’s disease with neurological symptoms and being dependent on her mother may explain insufficient hygiene in this case. In the second case, a narrow and deep umbilicus associated with obesity predisposed to omphalolith.
Omphalolith usually remains asymptomatic for several years. I can be noticed by chance or after secondary complications (3). Repetitive trauma can cause irritation, erosions, bleeding, and pyogenic granuloma. Secondary infection, abscess formation, cellulite, or even peritonitis can also be the revealing symptoms of this condition (3,4,6) .
The diagnosis of omphalolith is based on clinical examination. Dermoscopy shows aggregates of pigmented keratin. If a histopathological examination is performed, it reveals laminated keratin associated with amorphous sebaceous material.
Differential diagnoses include malignant tumors comprising Mary Joseph’s nodule and malignant melanoma. Benign affections can mimic umbilical concretion such as keloids, umbilical endometriosis, dermatofibroma, and persistent omphalomesenteric duct (1,2,6). Therefore, early recognition of omphalolith is important to prevent unnecessary investigations.
The treatment consists of a gentle extraction of the calculus using forceps (5,6). In our cases, it allowed the extraction of the entire mass with no bleeding. Excision of an associated pyogenic granuloma can be necessary in some cases. Patients’ education on proper corporeal hygiene is paramount to prevent recurrences (3,4,6).  The excision of the umbilicus may be recommended in some recalcitrant cases(1).