Accessory Cavitated Uterine Myometrium in a Perimenopausal Woman Presenting as a Large Uterine Mass with Severe Dysmenorrhea: A Case Report

Accessory Cavitated Uterine Myometrium (ACUM) is a rare Müllerian anomaly characterized by an isolated endometrium - lined cavity within the myometrium. It commonly presents in young women with severe dysmenorrhea and is often misdiagnosed as adenomyosis or leiomyoma. We report a case of a 43 - year - old woman presenting with chronic lower abdominal pain and severe dysmenorrhea for three years. She had regular menstrual cycles with prolonged and heavy bleeding. Clinical examination reveal ed a mobile abdominopelvic mass corresponding to 16 – 18 weeks gestational size. Imaging suggested a localized intramyometrial lesion. Surgical exploration revealed a well - defined cavitated lesion within the myometrium containing altered blood. Histopathological examination confirmed the presence of an endometrial lining with surrounding smooth muscle hyperplasia, consistent with ACUM. This case is notable for its atypical age of presentation and highlights the importance of considering ACUM in the differenti al diagnosis of dysmenorrhea associated with uterine enlargement. Surgical management resulted in significant symptomatic relief.

Accessory cavitated uterine myometrium, ACUM, dysmenorrhea, Müllerian anomaly, adenomyosis mimic, uterine mass 1.

Accessory Cavitated Uterine Myometrium (ACUM) is a rare and distinct Müllerian anomaly characterized by a non - communicating cystic cavity within the myometrium lined by functional endometrium. It is increasingly being recognized as a separate clinical entity distinct from adenomyosis and other uterine pathologies. Typically, ACUM presents in adolescents or young women with severe dysmenorrhea that is often refractory to medical management. The lesion contains hemorrhagic content due to cyclical bleeding within the cavity, leading to progressive pain. The etiology is thought to involve duplication or persistence of Müllerian tissue during embryological development. Despite advances in imaging, ACUM is frequently misdiagnosed due to overlapping features with more common conditions such as fibroids and adenomyosis. This report describes an unusual case of ACUM in a perimenopausal woman, highlighting the diagnostic challenges and emphasizing the importance of considering this entity even beyond the typical age group. 2. Methodology A 43 - year - old multiparous woman presented with complaints of lower abdominal pain and severe dysmenorrhea for three years. The pain was cyclical, progressively worsening, and interfering with daily activities. Her menstrual cycles were regular, occurring every 30 days, but were prolonged with bleeding lasting 10 days. The flow was heavy, requiring approximately six sanitary pads per day. On E xamination • Per abdomen: A well - defined, mobile mass corresponding to 16 – 18 weeks size was palpable. • Per vaginal examination: Uterus was enlarged to 16 weeks size, bilateral fornices were free, and no tenderness was noted. Ultrasonography revealed a bulky uterus with a localized intramyometrial lesion. Based on clinical findings, provisional diagnoses included adenomyosis and fibroid uterus. The patient was planned for surgical management. Intraoperatively, a well - circumscribed cavitated lesion was identified within the myometrium, separate from the endometrial cavity. The cavity contained thick, chocolate - colored fluid. Surgical excision of the lesion laparoscopic hysterectomy was performed. The specimen was sent for histopathological examination. 3.

and Discussion ACUM is a rare entity that poses a diagnostic challenge due to its resemblance to more common uterine conditions. It is defined by the presence of a cavitated lesion within the myometrium, lined by functional endometrium and surrounded by smooth muscle. Paper ID: SR26322114652 DOI: https://dx.doi.org/10.21275/SR26322114652 1319 International Journal of Science and Research (IJSR) ISSN: 2319 - 7064 Impact Factor 2025: 7.089 Volume 15 Issue 3, March 2026 Fully Refereed | Open Access | Double Blind Peer Reviewed Journal www.ijsr.net In this case, the patient presented at 43 years of age, which is atypical. Most reported cases occur in younger women, making this presentation unusual and clinically significant. The clinical findings of an enlarged uterus and severe dysmenorrhea initially suggested adenomyosis or fibroid uterus. However, intraoperative identification of a localized cavity containing altered blood pointed towards ACUM. Operative Findings Enlarged uterus (~16 – 18 weeks size) Well - defined intramyometrial cystic lesion No communication with uterine cavity Thin serous fluid of approximately 30ml within cavity Histopathological Findings Microscopic examination revealed: Cystic cavity lined by endometrial glands and stroma Surrounding smooth muscle hyperplasia Areas of hemorrhage and hemosiderin - laden macrophages No evidence of malignancy These findings confirmed the diagnosis of ACUM. Differential Diagnosis Adenomyosis (diffuse involvement rather than localized cavity) Degenerating fibroid (absence of endometrial lining) Rudimentary uterine horn (usually communicates or associated with anomalies) Management Surgical excision remains the definitive treatment. Removal of the lesion leads to complete resolution of symptoms. In this patient, postoperative recovery was uneventful with significant relief in dysmenorrhea. 4. Operative Photographs (Captions) Figure 1: Intraoperative image showing enlarged uterus with a well - defined bulge over the myometrium Figure 2: Excised specimen showing a cystic lesion within the myometrium Figure 3: Cut section of the specimen revealing a well - circumscribed cavity lined by endometrial tissue Figure 4 : Histopathology Photograph: Surrounding smooth muscle hyperplasia around the cavity (H&E stain) 5.

Accessory Cavitated Uterine Myometrium is a rare and underdiagnosed condition that should be considered in women presenting with severe dysmenorrhea and uterine enlargement. Although commonly reported in younger patients, it can also occur in perimenopausal women, as demonstrated in this case. Accurate diagnosis requires a combination of clinical suspicion, imaging, and histopathological confirmation. Surgical management is curative and significantly improves quality of life. Greater awareness of this entity can help prevent misdiagnosis and ensure timely and appropriate treatment.

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