Cutaneous Endometriosis

Endometriosis is a gynecological condition characterized by the presence of endometrial-like tissue outside the uterus, typically at sites including the ovary, uterosacral ligaments, ovarian fossa, the pouch of Douglas, and the bladder, thought to be precipitated by genetic and epigenetic mutations that can predispose individuals to the disease, leading to infertility and immune system alterations. Contrary to the long-held belief that endometriosis is a progressive and recurrent disease, research indicates that most lesions are self-limiting due to fibrosis and immune response. Emerging research emphasizes the role of immune dysfunction, hormonal influences, and environmental factors in disease onset and progression. The condition presents with diverse symptoms, including pelvic pain, dysmenorrhea, and infertility, but its progression and severity vary among individuals. Diagnosis remains challenging, often leading to delayed recognition, with surgical assessment via laparoscopy historically considered the gold standard. Please see StatPearls' companion resource, "Endometriosis," for further information. Additionally, endometriosis can occur at extrapelvic/extragenital sites. Cutaneous endometriosis can be placed into the subtype of extrapelvic endometriosis. Cutaneous endometriosis is a rare condition commonly classified as primary or secondary types. Secondary cutaneous endometriosis usually develops after surgical procedures, eg, cesarean sections or laparoscopies; primary cutaneous endometriosis occurs spontaneously in <30% of cases. Primary cutaneous endometriosis arises without prior surgery, most frequently affecting the umbilicus, also known as "Villar's nodule."  The condition typically manifests as a palpable, discolored skin lesion that may fluctuate in size and symptoms, including pain and bleeding over the affected sites on the skin in response to hormonal changes during the menstrual cycle. Scar or iatrogenic endometriosis is the term used for endometriosis that occurs in surgical scars, which can be cutaneous or subcutaneous, depending on the location of the lesions.  Diagnosis requires a biopsy, as its appearance overlaps with various other conditions, including metastases and benign skin lesions. Surgical excision is the primary treatment, though hormonal therapy may be considered for symptom management. The underlying mechanisms of cutaneous endometriosis are still debated, with theories including metaplasia, lymphatic spread, and iatrogenic implantation. While generally benign, rare cases of malignant transformation have been reported. Imaging techniques like ultrasound and MRI aid in diagnosis, but histopathological examination remains the gold standard. Understanding the complex origins and mechanisms of cutaneous endometriosis is crucial for developing more effective diagnostic and therapeutic approaches.