Challenging Diagnosis of Mesenteric Mucinous Adenocarcinoma Clinically Suspected Primary Ovarian Malignancy: Rare Presentation

<b>Abstract: </b> A 37-year-old woman presented with lower abdominal pain, palpable mass in the left lower quadrant, nausea, vomiting, and absence of bowel movements. Initial ultrasound suggested a 9cm fibroid, however, MRI and CT scans revealed a malignant central mass with significant ascites, suspecting a mesenteric hematoma. Elevated CA-125 prompted further investigation. Surgical intervention revealed a large mesenteric mass, leading to a midline laparotomy, left salpingo?oophorectomy, and sigmoid colectomy. Pathology confirmed well-differentiated mesenteric mucinous adenocarcinoma with an unclear primary origin, possibly ovarian. Postoperative follow-up included regular CA-125, CEA monitoring, and periodic CT scans. Despite extensive evaluations, the primary origin remained undetermined. The patient is under regular follow-up. This case highlights the diagnostic challenges and importance of a multidisciplinary approach and emphasises the need for individualised patient management strategies. <b>Keywords:</b> Mesenteric mucinous adenocarcinoma; Mesenteric mass; ovarian cancer; Diagnostic challenge; Multidisciplinary approach