Immunohistochemical Analysis of an Ectopic Endometriosis in the Uterine Round Ligament
A rare case of the inguinal endometriosis was reported with immunohistochemical analysis. A 28-year-old woman had a thumb-sized tumor in the right groin for two years with a gradual increase in size and pain. An operation revealed an elastic hard tumor with an unclear margin and adhesion to the uterine round ligament. The histology showed irregular proliferation of the endometrial glands and stroma.
Abstract
A rare case of the inguinal endometriosis was reported with immunohistochemical analysis. A 28-year-old woman had a thumb-sized tumor in the right groin for two years with a gradual increase in size and pain. An operation revealed an elastic hard tumor with an unclear margin and adhesion to the uterine round ligament. The histology showed irregular proliferation of the endometrial glands and stroma. The glandular epithelium stained weakly positive against CD125 antibody and the stromal matrix stained strongly positive against CD10 antibody. The nucleus in both the epithelial and stromal cells stained strongly positive against progesterone and estrogen receptor antibodies, and the cytoplasm in both types of cells stained moderately positive against COX-2 (cyclooxygenase-2) antibody. In conclusion, the combination of estrogen or progesterone receptor antibody for the nucleus and CD10 or COX-2 antibody for the cytoplasm could enhance the accuracy of diagnosis for ectopic endometriosis.
Outline Background
Endometriosis is an ectopic occurrence of tissue morphologically and functionally resembling endometrial tissue that is implanted into regions other than the uterus [1]. Although endometriosis occurs most frequently in the intrapelvic organs, many cases of extrapelvic endometriosis throughout the body have been reported. Since Sampson [2] labeled extrauterine adenomyosis as endometriosis, occurrences have been reported not only in intrapelvic tissue including the Douglas fossa, the posterior and anterior cul-de-sacs of the pelvis peritoneum, uterosacral ligaments, the rectum, the colon, and the oviducts, but also in extraperitoneal tissue including the liver [3], the lung [4], and both the cerebral [5] and peripheral nerves [6,7]. Even in extraperitoneal endometriosis, inguinal subcutaneous endometriosis was rarely reported, with an occurrence rate of 0.3~0.8% [1,8-10].
Recent progress in immunohistochemistry has found that CD10 and cyclooxygenase-2 (COX-2) could be important markers for endometrial tissue. Although CD10 is known as a common surface marker of acute lymphoblastic leukemia, it is also expressed in epithelial cells including renal tubular and glomerular cells, breast and salivary gland myoepithelium, prostatic glandular epithelium, and pulmonary alveolar lining cells. However, in endometriosis, CD10 is not expressed in glandular epithelial cells, but in stroma [11,12]. In contrast, COX-2 is a prostaglandin hydroperoxidase, which synthesizes PGH2 from PGG2 during the processes of inflammation, proliferation, and differentiation, and is expressed in macrophages, fibroblasts, vascular endothelial cells, neurons, and chondrocytes. It is also related to reproductive endometrium, which produces PGE2 and PGF2α[13,14]. Since we presented an inguinal subcutaneous tumor mass with a postoperative pathological diagnosis of ectopic endometriosis occurring in the uterine round ligament, the purpose of the immunohistochemical analysis in this case report is to compare the stainability of newly applied antibodies to conventional antibodies against CA125, estrogen, and progesterone receptors, to reveal the mechanism of the disease, and to determine the most sensitive procedure for detecting an ectopic endometrial tissue.
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