Spontaneous cutaneous endometriosis in the mons pubis region: a case report diagnosed by fine-needle aspiration biopsy.

Most cutaneous endometriosis develops at the site of an abdominal surgical scar. Spontaneous cutaneous endometriosis is extremely rare. We report a case of spontaneous cutaneous endometriosis in the mons pubis region. A 41-year-old woman presented with a mass in the right mons pubis, causing cyclic pain associated with menses. Fine-needle aspiration (FNA) biopsy was performed. The smears contained three cellular components: honeycombed sheets of glandular epithelial cells, fragments of ovoid-to-spindle shaped stromal cells, and background inflammatory cells, including hemosiderin-laden macrophages, histiocytes, and neutrophils. Biphasic clusters of glandular epithelial cells and stromal cells were identified. FNA cytology is a safe and useful adjunctive tool for diagnosing cutaneous endometriosis.