Deciduosis of the Appendix During Pregnancy

Abstract

Acute appendicitis is an important differential diagnosis in patients with right lower quadrant pain during pregnancy. Endometriosis, a hormone-related pathology, is another possibility. Patients with endometriosis are typically symptomatic before pregnancy. Stromal endometriosis is a variant of endometriosis that presents no symptoms before pregnancy but which occasionally presents with the new onset of symptoms during pregnancy. We report the case of a 35-year-old woman in her 8th month of pregnancy who presented with impending appendiceal rupture due to deciduosis of the appendix, a progesterone-related condition, during pregnancy. This case suggests that deciduosis/stromal endometriosis should be considered as a differential diagnosis of acute abdomen during pregnancy, even if the patient is asymptomatic before pregnancy.

Keywords: appendicitis; decidualization; deciduosis; ectopic decidua; endometriosis; stromal endometriosis.

Figure 1.

The resected specimen macroscopically shows swelling of the entire appendix and surrounding adipose tissue.

Figure 2.

A: The appendiceal wall is completely occupied by multiple nests of cells with foamy or eosinophilic cytoplasm. [Hematoxylin and Eosin (H&E) staining, original magnification ×15]. B: A high-power view of the nest located in the mucosal layer. Morphologically, cells forming the nest appear to be decidualized endometrial stromal cells (H&E staining, original magnification ×100). C, D: On immunohistochemistry, nuclear staining for anti-progesterone receptor antibodies (C) and cytoplasmic staining for CD10 antibodies (D) are positive, indicating that the cells have features of endometrial stromal cells (Immunoperoxidase method, original magnification ×100).