Decidualization of Endometriosis in Macaques

Abstract

The decidua is the superficial portion of endometrium that transforms, or decidualizes, under the influence of progesterone to nourish the early embryo during pregnancy. Deciduae outside the uterus are found in nearly 100% of human pregnancies. This condition, known as deciduosis, may mimic malignancy, resulting in additional diagnostic procedures that place the mother, baby, or both at risk. Deciduosis has been described in both Old World and New World nonhuman primates in conjunction with pregnancy and after treatment with exogenous progestins. Here the authors present 6 cases of deciduosis associated with endometriotic lesions in female rhesus and cynomolgus macaques (Macaca mulatta and Macaca fascicularis). Full diagnostic necropsies with histologic analyses were performed on all animals. Deciduae were stained with hematoxylin and eosin and by immunohistochemistry for vimentin, CD10, progesterone receptor, estrogen receptor, desmin, cytokeratin, kermix P8, chorionic gonadotropin, human placental lactogen, and calretinin. The most common clinical signs were abdominal pain (4 of 6) and anorexia (2 of 6). At necropsy, macaque uteri were often enlarged or disfigured (4 of 6) with abundant fibrous adhesions (5 of 6). Affected tissue consisted of epithelial-lined cysts and decidualized stroma with scattered gamma/delta T cells. Decidualized stromal cells were large and polyhedral with abundant cytoplasm and round vesicular nuclei. They stained positive for vimentin, CD10, progesterone, and estrogen. In summary, these cases illustrate deciduosis in 6 nonhuman primates with endometriosis. Understanding decidualization in nonhuman primates will aid in elucidating the pathophysiology of deciduosis during pregnancy or endometriosis and potentially lead to new interventions.

Keywords: disease process; immunohistochemistry; infectious; laboratory animals; other; primate; reproductive; species; technology; tissue.

Figure 1

Decidualized endometriosis, abdominal cavity, rhesus macaque, case 1. Fibrous adhesions between the omentum and other abdominal organs causing a mass of roughened, fused intestinal loops with irregular serosal surfaces (arrows).

Figures 2–9

Decidualized endometriosis, rhesus macaque, cases 1 and 3. Figure 2. Large islands of polygonal cells (asterisks) are compressed by adjacent fibrous connective tissue and blood-filled, pseudocolumnar to columnar epithelium-lined cysts characteristic of endometriosis (epithelial lining not visible at this magnification). HE. Figure 3. Islands of polygonal decidualized endometrial stromal cells with abundant eosinophilic cytoplasm are separated and surrounded by fibrous connective tissue, lymphoplasmacytic perivascular inflammation, small foci of hemosiderosis, and hemorrhage. HE. Figure 4. A large endometrial gland, lined by ciliated epithelium and filled with cellular debris, is surrounded by decidualized endometriosis stroma. HE. Figure 5. Decidualized cells are polygonal, lack distinct cellular borders and contain large, vesicular nuclei. Small, dense endometrial granular leukocytes (small arrows) are present. HE. Figure 6. Vimentin immunohistochemistry demonstrates strong cytoplasmic immunoreactivity of the decidualized stromal cells. Figure 7. CD10 immunohistochemistry demonstrates moderate cytoplasmic immunoreactivity within decidualized stromal cells. Figure 8. Estrogen receptor immunostaining showing strong nuclear immunoreactivity within decidualized stromal cells. Figure 9. Progesterone receptor immunostaining showing strong nuclear immunoreactivity within decidualized stromal cells.