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 of 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
or baby or both at risk. Deciduosis has been described in both Old 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 histological analyses were performed on all
animals. Deciduae were stained with hematoxylin & 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.