Intracystic septal biopsy in a multilocular pelvic cyst-A case report.

A 42-year-old woman with a history of open adenomyomectomy presented with lower abdominal discomfort in October 2025. Pelvic MRI revealed a multilocular cystic mass measuring approximately 15.2 × 10.2 × 11.7 cm in the left adnexal region, suggestive of a mucinous tumor, with borderline or malignant disease not excluded. Tumor markers were within normal limits. Imaging demonstrated multiple intracystic septa, some of which were thick and irregular, without definite enhancing solid nodules. Given the surgical history, a pelvic inclusion cyst was considered, although a neoplastic lesion could not be ruled out. The patient underwent ultrasound-guided percutaneous aspiration and sclerotherapy under intravenous anesthesia. A 16G needle was used to aspirate approximately 700 mL of brown cyst fluid. The cavity was irrigated repeatedly with saline until clear, followed by instillation of 400 mL of 95% ethanol for approximately 15 minutes. After ethanol exposure, targeted biopsy of the thick septa was performed using a 14G automated biopsy device, yielding four tissue specimens. Finally, the ethanol was completely aspirated, resulting in complete collapse of the cyst cavity. Histopathological examination revealed intestinal mucosa, smooth muscle, and fibrofatty tissue with focal fibrosis, hemorrhage, and mild inflammatory cell infiltration, indicating that the sampled “septa” originated from adherent bowel wall. The patient recovered well, resumed oral intake on the day of the procedure, and experienced only mild nausea on the first postoperative day. No abdominal pain, fever, or peritoneal irritation was observed, and laboratory tests showed no evidence of infection. No delayed bowel-related complications occurred during follow-up. No recurrence was observed at 3 months.

This case report was conducted in accordance with institutional policy and was exempt from formal ethics committee review.

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Intracystic septal biopsy represents a potential tissue acquisition strategy in multilocular cystic lesions, particularly in cases lacking solid components. This case provides preliminary evidence of its technical feasibility. However, careful consideration of anatomical context is necessary to balance diagnostic benefit and procedural safety. Further studies are needed to validate its applicability across different types of cystic lesion ( Fig. 1 ). Fig. 1 Imaging, intraoperative, and histopathological findings of a multilocular pelvic cystic lesion. (A, B) MRI demonstrating a large multilocular cystic lesion with multiple septa but no definite solid nodules. (C) Ultrasound-guided biopsy targeting a thick intracystic septum. (D) Histopathology revealing intestinal mucosa and smooth muscle, indicating that the imaging-defined septum corresponded to adherent bowel rather than a true intracystic structure (hematoxylin and eosin stain, × 100). Fig 1 dummy alt text Imaging, intraoperative, and histopathological findings of a multilocular pelvic cystic lesion. (A, B) MRI demonstrating a large multilocular cystic lesion with multiple septa but no definite solid nodules. (C) Ultrasound-guided biopsy targeting a thick intracystic septum. (D) Histopathology revealing intestinal mucosa and smooth muscle, indicating that the imaging-defined septum corresponded to adherent bowel rather than a true intracystic structure (hematoxylin and eosin stain, × 100).

Aspiration combined with sclerotherapy is widely used in the management of pelvic cystic lesions but is limited by the lack of histological confirmation. In clinical practice, diagnosis often relies on cyst fluid cytology, which has limited sensitivity (approximately 50%) due to insufficient tumor cells and restricted sampling representativeness influenced by tumor type and cyst architecture [ 4 , 5 ]. In this context, obtaining reliable histological evidence in multilocular cysts without solid components remains challenging. In this case, biopsy targeting intracystic septa successfully yielded diagnostic tissue, demonstrating the technical feasibility of this approach. Compared with cyst fluid cytology, this method allows direct acquisition of structural tissue, potentially improving diagnostic representativeness. From a methodological perspective, this strategy extends conventional biopsy approaches from solid nodules to intracystic structures, representing a structure-targeted tissue acquisition concept [ 6 ]. However, this case also highlights an important limitation. Histopathological findings revealed that the targeted “septa” originated from adherent bowel, indicating that imaging-defined septa do not necessarily correspond to true intracystic structures. In patients with prior surgery or inflammatory conditions, adjacent organs may become incorporated into cystic lesions due to adhesions. Therefore, when performing intracystic septal biopsy, careful evaluation of patient history and imaging characteristics is essential to assess the nature of septa and minimize procedural risks. In addition, dynamic assessment of septal features, such as mobility or peristalsis on real-time imaging, may further aid in distinguishing true septa from adjacent structures.

During manuscript preparation, ChatGPT (OpenAI) was used solely to assist with language editing and translation. All scientific content and interpretation of results were performed and verified by the authors, who take full responsibility for the content of the manuscript.

Pelvic cystic lesions have diverse etiologies, including ovarian neoplasms, endometriosis, enteric lesions, and peritoneal inclusion cysts [ 1 ]. For patients who are not suitable for or decline surgical treatment, aspiration combined with sclerotherapy has become an important minimally invasive alternative. In most of the cases, cytology exam were done to rule out malignancy after procedure. However, the lack of histological confirmation remains a major limitation [ 2 ]. In cystic lesions with solid components, biopsy targeting solid nodules can improve diagnostic accuracy [ 3 ]. However, in multilocular cystic lesions without definite solid structures, obtaining histological evidence remains challenging. Intracystic septa are a common feature of multilocular cysts and appear as membranous partitions on imaging. Theoretically, they may serve as potential targets for tissue sampling, but their clinical application has not been well established. In this study, we report a case of intracystic septal biopsy in a multilocular pelvic cyst and evaluate its technical feasibility and limitations.