Two previously unemphasized features of endometriosis: Micronodular stromal endometriosis and endometriosis with stromal elastosis

This report draws attention to two unusual features of the stromal component of endometriosis that can create problems in diagnosis. One of these is the exclusive presence of endometriotic stroma, so-called stromal endometriosis, that can occasionally take the form of microscopic nodules of endometriotic stroma on the pelvic peritoneum and other locations. This finding, which we refer to as a micronodular stromal endometriosis, can be overlooked entirely or lead to confusion with peritoneal involvement by low-grade endometrial stromal sarcoma. The other finding we describe is the presence of a prominent elastotic stromal response to endometriosis that can occasionally obscure or even focally obliterate the typical endometriotic stroma. This finding, although nonspecific, can be a diagnostic clue to the presence of endometriosis, especially when accompanied by the presence of the typical endometriod glands of that lesion.