Fulminant peritoneal metastasis of appendiceal mucinous adenocarcinoma during pregnancy: a case report

Abstract Background Appendiceal mucinous adenocarcinoma (AMA) is exceptionally rare, constituting less than 0.5% of all gastrointestinal malignancies and demonstrating an annual incidence of only 1 to 2 cases per million people. Furthermore, the majority of appendiceal adenocarcinomas are diagnosed at an advanced stage (Stage III and IV). A systematic literature review of the past 10 years revealed that only one case of aggressive appendiceal mucinous adenocarcinoma in pregnancy has been reported. Case presentation This case report presents a rare instance of fulminant peritoneal metastasis of appendiceal mucinous adenocarcinoma during pregnancy: A 34-year-old obese pregnant woman (BMI 40 kg/m²) initially presented with suppurative appendicitis at 28+ 1 weeks of pregnancy, which was resolved with a temporary clinical remission through conservative treatment with medication. However, the patient subsequently fulminant progression to Stage IV (T4NxM1) at 13 days. The primary tumor of the appendix perforated, leading to peritoneal seeding and metastasis to the ovary. This triggered the development of mucinous adenocarcinoma of the ovary, which exhibited explosive growth. During the procedure, the MDT implemented an epidural-general sequential anesthesia protocol, enabling a seamless transition between cesarean delivery and subsequent radical tumor resection. At the 18-month follow-up, both the mother and infant exhibited positive outcomes with no evidence of tumor recurrence. Although the short-term outcomes are favorable, the initial diagnosis of “suppurative appendicitis” resulted in delayed recognition of the malignant tumor. Conclusions This case provides critical insights into the dual paradigm shifts in the diagnosis and management of rare malignant tumors during pregnancy, thereby offering valuable clinical alerts and diagnostic guidance for clinicians. In terms of diagnostic reasoning, it emphasizes that clinicians should critically appraise the conventional diagnosis of “appendicitis” and incorporate rare entities—such as “appendiceal mucinous adenocarcinoma with ovarian metastasis”—into the differential diagnosis of acute abdomen. This practice is pivotal for avoiding diagnostic delays arising from overreliance on empirical judgments. Additionally, optimizing standardized MDT protocols and striving to enhance the early diagnosis rate of rare malignant tumors represent essential approaches to addressing these complex clinical challenges.