Cutaneous endometriosis of the umbilicus (Villar's nodule).

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A 26-year-old Caucasian nulliparous woman with menorrhagia and dysmenorrhea presented to our dermatology clinic for initial evaluation of a tender papule in the umbilicus. The papule had been present for 2 years and initially appeared shortly after discontinuation of oral contraceptive therapy. She reported that during her menses, the papule became larger, more erythematous, and more symptomatic with bleeding and tenderness. When she was not menstruating, the lesion was smaller and only slightly tender to palpation. Physical examination revealed a 4 mm delicate pink-brown bilobed papule within the umbilicus (Fig. 1A and 1B). The papule was sensitive to light touch and palpation. Of note, the patient was not menstruating at the time of the physical examination. Snip biopsy testing of the papule revealed dilated intradermal endometrial glands within a fibrovascular stroma with extravasated red blood cells, consistent with cutaneous endometriosis (CEM; Fig. 2).

Fig. 1

(A) A 4 mm delicate pink-brown bilobed papule in the umbilicus; (B) dermoscopy revealing delicate vascular features.

Fig. 2

Snip biopsy test results from the umbilicus (hematoxylin-eosin, original magnification × 10): Dilated intradermal endometrial glands within a fibrovascular stroma with extravasated red blood cells.

Endometriosis, or functional endometrial tissue outside the uterus, is common and has been reported in nearly every organ system. CEM has been reported to account for <5.5% of diagnosed endometriosis (Kyamidis et al., 2011, Lopez-Soto et al., 2018). CEM typically occurs secondary to open surgical or laparoscopic procedures and occurs spontaneously <30% of the time. When occurring spontaneously, the umbilicus is the most common location (Kyamidis et al., 2011, Lopez-Soto et al., 2018, Victory et al., 2007). CEM of the umbilicus is also known as Villar’s nodule, named after the physician who described the condition in 1886 (Kyamidis et al., 2011, Lopez-Soto et al., 2018, Victory et al., 2007). Villar’s nodules have been reported to account for 3.2% to 40% of extragenital endometriosis (Victory et al., 2007). Several hypotheses have been proposed regarding the pathogenic mechanism of CEM, including metaplasia, venous metastasis, lymphatic metastasis, and iatrogenic implantation (Din et al., 2013).

Clinically, CEM presents as a tender brown, red, or blue papule or nodule. Its appearance and associated symptoms may fluctuate with the hormonal environment, and it may demonstrate catamenial bleeding. The differential diagnosis of Villar’s nodule is broad and includes Sister Mary Joseph nodule, cutaneous metastasis, keloid, urachal duct cyst, hernia, pyogenic granuloma, melanocytic nevus, and melanoma. Biopsy testing is necessary for a definitive diagnosis.

The histopathologic features of CEM include dilated intradermal endometrial glands lined by pseudostratified columnar epithelium in a fibrovascular stroma. Extravasated red blood cells often serve as a clue to the diagnosis. Cellular nuclei of glandular cavity walls may be positive on immunohistochemical staining for estrogen and progesterone receptors, and cells in the interstitium may be positive for CD10 (Fukuda and Mukai, 2010).

Definitive treatment of CEM includes excision (Din et al., 2013). Patients should be evaluated by a gynecologist, and hormonal therapy may be considered. Our patient was initiated on hormonal therapy with leuprolide by Gynecology, which resulted in near clinical resolution of the papule. Since then, she has been followed at our dermatology clinic for approximately 18 months with a maintained response to hormonal therapy and no plans for surgical excision. The patient hopes to start a family in the future. She was counseled that the CEM may recur when she discontinues her leuprolide.

CEM should be considered in the differential diagnosis of umbilical papules or nodules, particularly those that clinically fluctuate or bleed.

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