Endometrial stromal nodule, light micrograph. An endometrial stromal nodule is a benign lesion composed of endometrial stroma, usually seen in middle-aged women. It resembles low-grade endometrial stromal sarcoma; however, it is sharply circumscribed and does not invade blood vessels, lymphatics or myometrium. This low magnification view shows an endometrial stromal nodule at upper right (blue) and myometrium at lower left (pink).