Primary Small Intestinal Adenocarcinoma Presenting as Ovarian Metastasis With Obstructive Symptoms: A Case Report

Primary small-bowel adenocarcinoma (SBA) is a rare malignancy. As early symptoms are nonspecific, diagnosis is frequently delayed, and patients often present with advanced disease. Ovarian metastasis from SBA - classified as a Krukenberg tumor - is exceptionally uncommon and may obscure the underlying gastrointestinal origin, posing a significant diagnostic challenge. We report the case of a 39-year-old woman with a history of ulcerative colitis who presented with abdominal distension and was found to have a rapidly enlarging left ovarian mass. Left adnexectomy revealed adenocarcinoma, and further evaluation identified a circumferential ulcerative lesion in the upper jejunum. Immunohistochemical analysis demonstrated CK7 positivity, CK20 positivity, CDX2 positivity, and PAX8 negativity in both ovarian and jejunal specimens, confirming a diagnosis of primary jejunal adenocarcinoma with ovarian metastasis. The patient subsequently underwent laparoscopic partial jejunal resection. Histopathology confirmed stage IV disease (pT3 NX M1). Postoperatively, capecitabine and oxaliplatin (CAPOX) plus bevacizumab chemotherapy was initiated following colorectal cancer protocols. This case illustrates several diagnostic challenges associated with SBA, particularly when presenting as an ovarian mass. Ovarian metastasis from SBA is exceedingly rare, and the presence of bilateral, non-synchronous disease further complicates diagnosis. Immunohistochemistry played a key role in distinguishing the jejunum as the primary site. Ulcerative colitis may have contributed to carcinogenesis. Despite therapeutic advances, stage IV SBA remains associated with poor prognosis. This rare case of primary upper jejunal adenocarcinoma presenting as a Krukenberg tumor underscores the importance of thorough diagnostic evaluation, including immunohistochemical analysis. Multidisciplinary management and timely surgical intervention remain essential for both diagnosis and symptom control in advanced SBA.