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Epidemiology

Cutaneous endometriosis is a rare manifestation of endometriosis, accounting for approximately 0.5% to 1% of all endometriosis cases. It most commonly affects women of reproductive age who have undergone abdominal or pelvic surgeries, particularly cesarean sections. The incidence of cutaneous endometriosis following cesarean section is estimated to be between 0.03% and 1% (Steck & Helwig, 1965). Due to underreporting and misdiagnosis, the true prevalence may be higher than documented.

Reference: Steck, W. D., & Helwig, E. B. (1965). Cutaneous endometriosis. The Journal of the American Medical Association, 191(2), 167–170. doi:10.1001/jama.1965.03080020019005

Pathophysiology

The exact mechanism leading to cutaneous endometriosis is not fully understood, but several theories have been proposed. The most widely accepted is the iatrogenic implantation theory, which suggests that endometrial cells are transplanted to the skin during surgical procedures, such as cesarean sections or laparoscopic surgeries (Scher & Macura, 2007). Another hypothesis is the lymphatic or vascular dissemination theory, where endometrial cells spread through lymphatic or blood vessels to distant skin sites (Anderson & Kissane, 1972). Additionally, the coelomic metaplasia theory posits that multipotent mesenchymal cells differentiate into endometrial tissue under certain stimuli.

References

Scher, D. L., & Macura, K. J. (2007). Endometriosis of the abdominal wall. AJR American Journal of Roentgenology, 189(5), 1164–1167. doi:10.2214/AJR.07.2314 Anderson, M. C., & Kissane, J. M. (1972). Smooth-muscle differentiation of stromal endometriosis. Obstetrics & Gynecology, 39(4), 591–598.

Clinical Presentation

Patients with cutaneous endometriosis typically present with a palpable nodule or mass near a previous surgical scar, which may be painful or tender. A hallmark of the condition is cyclic pain and swelling that coincide with the menstrual cycle, due to hormonal responsiveness of the ectopic endometrial tissue (Blanco et al., 2003). The overlying skin may appear normal or exhibit discoloration ranging from bluish to brown.

Reference: Blanco, R. G., Parithivel, V. S., Shah, A. K., Gumbs, M. A., Schein, M., & Gerst, P. H. (2003). Abdominal wall endometriomas. The American Journal of Surgery, 185(6), 596–598. doi:10.1016/S0002-9610(03)00080-0

Differential Diagnosis

The differential diagnosis for cutaneous endometriosis includes a variety of conditions that present as abdominal wall masses. These conditions include surgical scar hernias, lipomas, hematomas, abscesses, sebaceous cysts, neuromas, and neoplasms such as desmoid tumors or soft tissue sarcomas. Distinguishing cutaneous endometriosis from these conditions is crucial for appropriate management (Horton et al., 2008). Clinical suspicion is heightened by a history of pelvic surgery and cyclical symptoms related to menstruation.

Reference: Horton, J. D., DeZee, K. J., Ahnfeldt, E. P., & Wagner, M. (2008). Abdominal wall endometriosis: A surgeon's perspective and review of 445 cases. The American Journal of Surgery, 196(4), 450–455. doi:10.1016/j.amjsurg.2008.06.009

Diagnostic Imaging

Ultrasound is often the first-line imaging modality used to evaluate suspected cutaneous endometriosis, typically revealing a hypoechoic or heterogeneous mass adjacent to the abdominal wall (Zakhour & Leffall, 1980). Magnetic resonance imaging (MRI) offers superior soft-tissue contrast and can help delineate the extent of the lesion, showing characteristic findings such as hyperintense signals on T1-weighted images due to the presence of blood products.

Reference: Zakhour, B. J., & Leffall, L. D. (1980). Endometriosis of the abdominal wall. Journal of the National Medical Association, 72(10), 1047–1049.

Histopathology

Definitive diagnosis is achieved through histopathological examination of excised tissue. The hallmark findings include the presence of functional endometrial glands and stroma within the dermis or subcutaneous fat. Repeated hemorrhage within the lesion can lead to surrounding fibrosis and the accumulation of hemosiderin-laden macrophages (Redwine, 1988). Immunohistochemical staining may aid in the diagnosis by highlighting estrogen and progesterone receptor positivity in the ectopic endometrial tissue.

Reference: Redwine, D. B. (1988). Age-related evolution in color appearance of endometriosis. Fertility and Sterility, 49(5), 763–769. doi:10.1016/S0015-0282(16)59858-7

Treatment

Surgical excision with wide margins is the treatment of choice for cutaneous endometriosis and is usually curative. Complete removal of the lesion reduces the risk of recurrence and alleviates symptoms. In cases where surgery is contraindicated or incomplete excision is achieved, hormonal therapies such as oral contraceptives, progestins, or gonadotropin-releasing hormone (GnRH) agonists may be utilized to manage symptoms, although they are associated with higher recurrence rates (Nominato et al., 2010).

Reference: Nominato, N. S., Prates, L. F., Lauar, I., Morais, J., Maia, L., & Geber, S. (2010). Scar endometrioma following obstetric surgical incisions: Retrospective study on 33 cases and review of the literature. São Paulo Medical Journal, 128(2), 102–107. doi:10.1590/S1516-31802010000200007

Prognosis and Complications

The prognosis after complete surgical excision of cutaneous endometriosis is generally excellent, with low rates of recurrence. However, incomplete removal of the lesion can lead to persistent symptoms and recurrence of the mass. Although exceedingly rare, malignant transformation of cutaneous endometriosis into forms such as endometrioid carcinoma or sarcoma has been reported, highlighting the importance of accurate diagnosis and management (Giannella et al., 2010).

Reference: Giannella, L., La Marca, A., Tafi, E., Cubeddu, M., & Cianciulli, D. (2010). Surgical scar endometriosis after Cesarean section: A case report. Gynecological Endocrinology, 26(11), 834–836. doi:10.3109/09513590.2010.487602

Psychological Impact and Patient Counseling

Cutaneous endometriosis can significantly impact a patient's quality of life due to chronic pain and discomfort. Psychological support and thorough patient counseling are essential components of management. Educating patients about the nature of the disease, treatment options, and the importance of follow-up can improve adherence to therapy and overall satisfaction (Lankford & Kebede, 2017).

Reference: Lankford, C. L., & Kebede, A. (2017). Endometriosis of abdominal wall: Case report of presentation 40 years after surgical intervention. Case Reports in Obstetrics and Gynecology, 2017, 1–3. doi:10.1155/2017/5432797