Indian Journal of Pathology and Oncology 2021;8(4):522–525 Content available at: https://www.ipinnovative.com/open-access-journals Indian Journal of Pathology and Oncology Journal homepage: www.ijpo.co.in Case Report Serous borderline tumour of the peritoneum- A rare entity Sandhyarani Mahadev Kanna 1, *, Nidha Gaffoor 1 , Himasree E 1 , Nikhil P V 1 , Archana Shetty 1 , Supriya Sandeepa 1 , Bhargavi K N 1 1 Dept. of Pathology, Dr Chandramma Dayanand Sagar Institute of Medical Sciences & Research, Ramnagara, Karnataka, India ARTICLE INFO Article history: Received 11-08-2021 Accepted 18-09-2021 Available online 23-11-2021 Keywords: Mesothelial hyperplasia Primary peritoneal carcinoma Serous borderline tumor ABSTRACT Serous borderline tumor is a rare entity of peritoneum which can lead to diagnostic dilemma due to its resemblance with reactive lesions of peritoneum and ovarian borderline and malignant neoplasms. Complete clinical details, histopathological evaluation and immunohistochemistry aid in arriving at correct diagnosis. Recognizing this entity is important as it carries good prognosis. This is an Open Access (OA) journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. For reprints contact: reprint@ipinnovative.com 1. Introduction Serous borderline tumor (SBT) of the peritoneum is a rare low grade proliferative serous epithelial tumor, fundamentally arising in the peritoneum, 1 without underlying tissue invasion. 2 In SBT of the peritoneum, bilateral ovaries and fallopian tubes are macroscopically and microscopically normal. Ovary may show minimal ovarian cortical involvement less than 5 × 5 mm 2 . 2 Prior to the establishment of the term “SBT peritoneum”, various other nomenclatures were utilized to describe this entity, such as primary papillary peritoneal neoplasia, atypical endosalpingiosis and peritoneal serous micropapillomatosis of low malignant potential. 3 Serous borderline tumor is an incidental finding most of the time during laparoscopic procedures done for other clinical indications. 2. Case Report A 20-year old unmarried female patient presented to the Obstetric and Gynaecology department with irregular menstrual cycles since 1 year. She had no history of pain abdomen, dysmenorrhea, urinary or bowel symptoms. * Corresponding author. E-mail address: doc.sandhyamadhu@gmail.com (S. M. Kanna). There was no history of loss of weight or loss of appetite and no previous history of tuberculosis. Past history revealed inguinal hernioplasty at 9 years of age. There was no history of any malignancy in the family members. Ultrasonography abdomen and pelvis showed normal sized uterus, retroverted, endometrial thickness of 5.8mm. Multiple intercommunicating oblong cystic lesions with internal septations were separately seen from right ovary collectively measuring 5.2 x 4.2cm with a possibility of paraovarian cyst. No free fluid or lymph node enlargement was noted. Bilateral adnexae were normal. CA 125 was within normal limits. After pre-anesthesia checkup, covid testing and informed written consent, patient was taken up for surgery under general anesthesia for diagnostic and therapeutic cystectomy. A retroperitoneal multiloculated cyst (7x6 cms) was noted. Laparoscopic cystectomy and marsupialization of the cyst was performed. Clear serous fluid was drained. Inner surface of cyst was smooth with no papillary excrescences. Separate small papillary excrescences with calcific material approximately 5mm across were seen throughout the pelvis especially on the right ovary, pouch of Douglas, and uterosacral ligaments. Left ovary was unremarkable. There were no adhesions in pelvis. A differential diagnosis of miliary https://doi.org/10.18231/j.ijpo.2021.109 2394-6784/© 2021 Innovative Publication, All rights reserved. 522