Isolated Endometriosis on the Rectus Abdominis Muscle in Women without a History of Abdominal Surgery: a Rare and Intriguing Finding

We report 2 rare cases of endometriosis on the rectus abdominal muscle diagnosed incidentally during an operation for inguinal hernia repair in women with no surgical history. Two women sought medical attention for a mass found in the pubic abdominal wall. Only 1 woman reported occasional pain. At physical examination in both women, an ovoid swelling in the right pubic area was felt. One woman experienced pain on palpation, and one reported slight discomfort. Ultrasonography demonstrated a heterogeneous hypoechogenic formation with indistinct edges; diagnosis was difficult. Routine clinical and instrumental (pelvic ultrasonography) gynecologic examination in both patients performed shortly before hospitalization had not revealed any macroscopic focus of endometriosis in the pelvic region. At surgery, a lesion consistent with the diagnosis of endometriosis was found, which was confirmed at histologic analysis. These cases could represent the consolidation of different theories of endometriosis diffusion. We suggest including endometriosis in the differential diagnosis of a symptomatic mass in the abdominal wall in women with and without a surgical history.