The Metrial Gland in the Rat and Its Similarities to Granular Cell Tumors

Abstract

Metrial glands are normal structures located in the mesometrial triangle of the pregnant rat uterus from gestational day (GD) 8 through termination of pregnancy. Metrial glands are composed of a dynamic mixed cell population of granulated metrial gland (GMG) cells, endometrial stromal cells, trophoblasts, blood vessels, and fibroblasts. Collections of similar cells may be seen in association with pseudopregnancy and other hormonal disturbances. Granulated metrial gland cells are the hallmark cell of the metrial gland. They are bone-marrow-derived, perforin-positive, natural killer cells that proliferate in the pregnant uterus. Understanding the normal histogenesis of the metrial gland and recognizing the possible existence of GMG cells and a reactive metrial gland in the nonpregnant state are important when examining any uterine lesion that contains granulated cells. This report demonstrates that the cellular composition, morphology, and immunohistochemical staining profile of normal metrial glands are similar to reported granular cell neoplasms in rats and mice. The possibility of a non-neoplastic lesion involving the metrial gland should be considered when proliferative lesions involving granulated cells are observed in the uterus of mice and rats from nonclinical toxicity studies. Positive immunohistochemical staining for perforin and S100 would assist in the classification of such lesions as a reactive metrial gland or decidual reaction.

Characterization of immune cells and cytokine localization in the rat utero-placental unit mid- to late gestation

“…The distribution of both perforinand IFN␥-positive cells was observed in the perivascular regions of the spiral arteries at both GD15.5 and GD18.5. Our observed perforin-positive cell staining was consistent with uNK cell/granulated metrial gland cell staining previously described in the rat placenta (Head et al, 1994;Picut et al, 2009;Sladek et al, 1998).…”

“…At GD14-15 initiation of trophoblast invasion into the decidua and large quantities of dispersed perforin-positive uNK cells are observed in the mesometrial triangle. In late gestation perforin-positive granulated metrial gland cells were mainly localized in the perivascular regions of the mesometrial triangle (Picut et al, 2009). At GD18, deep trophoblast invasion and a significant reduction of uNK cells are observed (Ain et al, 2003).…”

Thyroid hormones affect decidualization and angiogenesis in the decidua and metrial gland of rats

“…After this period, at 14 DG there is a reduction in VEGF expression in all experimental groups, as we observed in this present study, which can be explained by a reduction in hypoxia, which also occurs physiologically (Plaisier 2011). Furthermore, from 14 DG, the decidua begins its regression (Picut et al 2009). Another important factor observed by Silva et al (2014) was the reduction of trophoblastic invasion of the maternal-fetal interface occurred in hypothyroid rats.…”

Proliferative and Nonproliferative Lesions of the Rat and Mouse Male Reproductive System

“…Granular cell tumor reacts positively in immunocytochemical stains for NSE, S-100 protein, and peripheral myelin proteins. In the female, it has been suggested that lesions termed granular cell tumors may in fact be normal or reactive metrial glands (Picut et al 2009). …”