Etiology is believed to be congenital, likely involving a müllerian duct abnormality. Diagnostic criteria proposed by Acién et al [1]., include 1) an isolated accessory cavitated mass, 2) normal uterus (endometrial cavity), tubes, and ovaries, 3) surgical excision with pathological confirmation, 4) accessory cavity lined by endometrial epithelium with glands and stroma, 5) chocolate-brown fluid content, and 6) absence of adenomyosis in the rest of the uterus.

Takeuchi et al [2]. described ACUM as a solitary myometrial cyst ≥1 cm surrounded by hypertrophic endometrium, independent of the uterine lumen, occurring in women ≤30 years with severe dysmenorrhea.

Naftalin et al [3]. suggested ultrasound features such as a myometrial mantle with a fluid-filled cavity showing echogenic or hyperechoic contents.

Complete surgical excision is curative and essential for symptom resolution. Although laparoscopic excision has been described, robotic-assisted excision offers enhanced dexterity and precision, especially beneficial for preserving myometrial integrity.

A 22-year-old unmarried, nulliparous woman presented with severe dysmenorrhea unresponsive to non-steroidal anti-inflammatory drugs and hormonal therapy for 2 years. Magnetic resonance imaging revealed a 1.4×1.3 cm cavitated mass in the right posterior cornual region medial to the uterotubal junction-consistent with ACUM.

The patient was placed in the lithotomy position under general anesthesia in steep Trendelenburg. A four-port robotic approach using the da Vinci Xi System (Intuitive Surgical, Sunnyvale, CA, USA) was utilized. A 1.5×1.5 cm bulging mass was visualized near the right round ligament. The patient(s) included in this video gave consent for publication of the video and posting of the video online, including social media, the journal website, scientific literature websites (such as PubMed, ScienceDirect, Scopus, etc.), and other applicable sites.

Bilateral tubes and ovaries were normal. No signs of pelvic endometriosis. Vasopressin was injected into the myometrium to reduce bleeding. A longitudinal incision was made over the mass; chocolate-colored fluid was drained. The ACUM was sharply dissected and enucleated with care to preserve surrounding myometrium.

The specimen was placed in an endobag and retrieved through the assistant port. Uterine defect was closed in two layers using 0-V-Loc barbed suture for watertight closure. Hemostasis was confirmed; pelvis irrigated and suctioned.

Results were operative duration of 60 minutes, estimated blood loss <15 mL, no complications, and patient discharged on postoperative day 1. Histopathology confirmed a cavitated lesion lined with benign endometrial glands and stroma, surrounded by myometrial mantle-findings consistent with ACUM.

This case highlights the significance of accurate diagnosis and surgical precision in managing ACUM. Robotic-assisted excision, as supported by prior literature [4], enables precise dissection and optimal uterine reconstruction. Intraoperative identification and complete excision are essential to avoid recurrence or misdiagnosis.

The primary goal remains symptom resolution and preservation of fertility. Long-term outcomes post-complete excision are favorable, with minimal risk of recurrence or obstetric complications.

Robotic-assisted excision of ACUM is an effective, minimally invasive, and fertility-sparing surgical technique. It provides excellent anatomical restoration and symptom relief with minimal complications, offering a preferred approach in young patients.