Ectopic Endometrium: The Pathologist's Perspective

Abstract

Endometriosis and adenomyosis are two frequent diseases closely linked, characterized by ectopic endometrium. Despite their benign nature, endometriosis and adenomyosis impair women's quality of life by causing pain and infertility and an increase in the incidence of gynecological malignancies has been reported. Since the first description of ectopic endometrium in 1860, different attempts have been made to describe, classify and understand the origin of these diseases. Several theories have been proposed to describe the pathogenic mechanism leading to the development of adenomyosis or endometriosis. However, all the hypotheses show some limitations in explaining all the different aspects and manifestations of these diseases. Despite the remarkable progress made over recent years, the pathogeneses of endometriosis and adenomyosis remain unclear. Moreover, because of the lack of standardized protocols and diagnostic criteria in pathology practice it is difficult to study and to classify these disorders. The goal of this review is to summarize the pathological aspects of adenomyosis and endometriosis, spanning a historical perspective to newly reported data.

Keywords: adenomyosis; endometrial cancer; endometriosis; histological diagnosis; ovarian cancer; pathological classification; pathology.

Figure 1

Macroscopic and microscopic appearance of adenomyosis. Thickened and trabeculated appearing myometrial wall with ill-defined hypertrophic swirls of smooth muscle of sectioned uterus with adenomyosis (a, inset). Histopathological image of uterine adenomyosis observed in hysterectomy specimen, with endometrial glandular and stroma invading the muscular myometrium (within circle) (a). Higher-power view showing ectopic endometrial glands and stroma surrounded by hyperplastic myometrium (asterisk) (b). Ectopic glandular epithelium is proliferative type and stroma is inactive, non-mitotic and composed of monotonous cells (b). A specimen showing an endometroid carcinoma infiltrating myometrial wall on the right (black line) and adenomyosis foci on the left (within line) (c). Hematoxylin and eosin stain.

Figure 2

Macroscopic and microscopic appearance of endometriosis in different sites. Macroscopic picture of ovarian endometrioma with fibrotic wall and a dense, dark brown content (a). Histopathological images of endometriotic implants in intestinal wall, fallopian tube, mesenteric adipose tissue, lymph node and diaphragm (b–f); m: intestinal mucosa; Ft: Fallopian tube; Ly: lymph node. The withe circles and the arrows highlight endometrial implants composed by several endometrial glands and stroma (b–f). Note the presence of hemosiderin-laden macrophages (asterisk) (f). Immunohistochemistry for CD10 shows strong expression in stroma surrounding an ectopic endometrial gland in the diaphragm (f inset). Hematoxylin and eosin stain.

Figure 3

Macro- and micro-photograph of endometrioma with malignant transformation in endometroid carcinoma. A 4 cm endometrioma with cystic and solid components and a papillary lesion arising from the cyst wall (a inset). Histopathological image of endometriotic cyst with wide lumen lined by a single layer of columnar epithelium without atypia surrounded by relatively scant stroma (a). Part of the cyst wall shows the eroded lining epithelium replaced by hemosiderin-laden macrophages (dark asterisk) (a) and part shows a proliferation of atypical glandular cells arranged in a papillary structure (white asterisk) and invading the stroma (arrow) (b). Higher-power view showing an atypical lining epithelium with hobnail cells, large vesiculated nuclei with prominent nucleoli, nuclear pleomorphism (white asterisk) (c). L: cyst lumen. Hematoxylin and eosin stain.