Low-Grade Serous Ovarian Carcinoma Presenting as a Pelvic Abscess With Transmural Caecal Involvement in a Young Woman: A Case Report

Low-grade serous ovarian carcinoma (LGSOC) is an uncommon epithelial ovarian malignancy with distinct clinicopathological behaviour compared with high-grade serous carcinoma.It often affects younger women, follows a relatively indolent course, and may present at an advanced stage.Presentation with a pelvic abscess and bowel involvement is unusual and may obscure the underlying diagnosis.We report the case of a 28-year-old woman who presented to the Department of Gynecologic Oncology at a tertiary healthcare centre with a 10-day history of progressively worsening lower abdominal pain, accompanied by fever and vomiting for 3 days.USG and MRI demonstrated a large, complex right ovarian mass with solid-cystic, hypervascular components, diffusion restriction, and suspicious enhancement characteristics, categorised as MR-O-RADS Category 5. Exploratory laparotomy revealed a complex pelvic mass with cavitation; pus was draining from the cavity, and the mass was protruding into the caecum.A surgeon was called, and the operation was performed collaboratively by the Gynecologic Oncology and surgical teams.The patient underwent resection of the ovarian mass, drainage of the pelvic abscess, right hemicolectomy, and omental resection.Frozen-section examination of the ovarian tissue revealed a malignant tumour composed of cuboidal cells arranged in papillary patterns, with oval nucleoli with polymorphism, and sporadic areas of necrosis and mitosis.Similar findings in the caecal growth suggested the presence of ovarian malignancy within the caecum.Histopathology confirmed low-grade serous carcinoma of ovarian origin with involvement of the right ovary and fallopian tube.The right hemicolectomy specimen showed metastatic serous carcinoma with transmural caecal infiltration.Immunohistochemistry (IHC) demonstrated CK7 positivity, oestrogen receptor positivity, focal weak WT1 positivity, CDX2 negativity, and weak or negative CK20 expression, supporting Müllerian origin rather than primary colorectal carcinoma.This case highlights that ovarian malignancy may mimic a tubo-ovarian abscess or pelvic sepsis, even in young patients, and that complex adnexal masses with suspicious imaging features require oncological vigilance and multidisciplinary management.