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Cutaneous endometriosis

Author: Brian Wu PhD. MD Candidate, Keck School of Medicine, Los Angeles, USA; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, November 2015. Revised November 2020


What is endometriosis?

Endometriosis is the growth of endometrial tissue (tissue that lines the womb and is shed as menstrual flow) outside the uterus (womb). It usually arises close to the uterus within the pelvis — the lower part of the abdomen. The mass is also called an 'endometrioma'. Endometriosis outside the pelvis occurs in about 12% of women with endometriosis.

What is cutaneous endometriosis?

Cutaneous endometriosis is endometriosis in the skin and is rare. It was first described by Villar in 1860. It commonly occurs in a surgical incision from a previous gynaecological or abdominal surgery, such as caesarean section, hysterectomy or laparoscopic surgery but can also develop spontaneously. It also called 'scar endometriosis'.

The most common sites for cutaneous endometriosis are the abdominal wall, umbilicus, vulva, and the extremities.

What causes cutaneous endometriosis?

There are two theories regarding the cause of spontaneous cutaneous endometriosis.

  • The transportation theory states that endometrial cells are transported outside the uterus via the lymphatic system or another route.
  • The metaplasma theory states that endometrial cells may develop in the coelomic mesothelium in the presence of high oestrogen levels or another stimulus.

What are the clinical features of cutaneous endometriosis?

Women with cutaneous endometriosis can present with the following signs and symptoms.

  • A palpable subcutaneous mass; this can cramp and bleed during the monthly period and is sometimes dubbed a “menstruating tumour”.
  • The mass is generally firm and may be blue, black, brown, or red in colour
  • Typical size range for the mass averages 0.5–6 mm in diameter.
  • The patient can complain of itching, swelling, or tenderness.

Cutaneous endometriosis of the perineum

What complications stem from cutaneous endometriosis?

Complications from cutaneous endometriosis include:

  • Local recurrence after surgical excision
  • Development of endometrial carcinoma (this is rare)

Malignancy should be suspected if the mass is abnormally large, has grown rapidly, or has recurred after previous excisions.

How is cutaneous endometriosis diagnosed?

Diagnosis of cutaneous endometriosis is based upon:

  • Patient history, including gynaecological and surgical history
  • Physical examination
  • Ultrasound test
  • Doppler examination of the soft tissues of the abdominal wall
  • Computer tomography (CT scan)
  • Magnetic resonance imaging (MRI)
  • Fine needle aspirate and cytology
  • Skin biopsy or excision specimen histology.

Cytology on fine needle aspirate or histopathology on skin biopsy or excision specimen is the key to accurate diagnosis and detects endometrial glands, stroma, and haemosiderin.

Diagnosis is often delayed due to confusion with other conditions, including haematoma, neuroma, hernia, and neoplastic tissue.

What is the treatment for cutaneous endometriosis?

The main treatment for cutaneous endometriosis is surgical excision of the mass, preserving the umbilicus if relevant.

Medical therapy uses the hormones danazol, progesterone, and gonadotrophin releasing hormone (GnRH).



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