Enigma of a Firm Umbilical Nodule.

Histopathological examination of the nodule revealed unremarkable epidermis and benign endometrial glands with surrounding cellular stroma and extravasated erythrocytes in the deep dermis [ Figure 3 ]. A final diagnosis of primary cutaneous endometrioma was rendered. The patient was referred to gynecology for further evaluation and complete surgical excision of the nodule. Endometriosis is a benign, chronic disorder affecting 5–15% of females of reproductive age. Cutaneous endometriosis is an uncommon entity seen in less than 5% of all cases of endometriosis.[ 1 ] Cutaneous endometriosis can be divided into either primary or secondary type depending on the origin, with secondary cases occurring because of inoculation of endometrial tissue into the abdominal wall post surgery.[ 2 ] When endometrial tissue arises in the skin without any preceding surgical procedure, it is classified as primary cutaneous endometriosis. Though etiology of the disorder remains largely unknown, metaplasia, vascular/lymphatic spread, or the role of umbilicus behaving like physiological scar has been postulated by some.[ 2 ] The patient can present with pain, bleeding during menses, or may be asymptomatic as well.[ 3 ] Lesions arising over or around umbilicus are challenging to diagnosis with the differentials to be considered include Sister Mary Joseph nodule (metastasis of abdominal cancer), cutaneous malignancy, cutaneous metastasis of internal malignancy, keloid, foreign body granuloma, hernia, congenital anomaly, lipoma, dermatofibroma, and abscess. Histopathology is the gold standard to make the diagnosis of cutaneous endometriosis showing presence of endometrial glands with hemorrhagic stroma in the surrounding tissue.[ 2 ] Dermoscopic findings of cutaneous endometriosis though unspecific have been reported to show a homogenous lesion with bluish blotch, polymorphous vascular pattern, a milky red or pink structureless area, and white lines.[ 1 , 4 ] Ultrasound can be done to rule out internal malignancy or hernia. Referral to gynecology department should be made to rule out other manifestations of endometriosis. When faced with an umbilical nodule, cutaneous endometriosis is one of the important differentials that needs to be kept in mind. The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Nil. There are no conflicts of interest.