Atypical Presentation of a Malignant Tumor of the Appendix: A Case Report.

A 56-year-old man presented with weight loss, abdominal pain, and altered bowel habits. Computed tomography revealed an appendiceal mass with hepatic lesions and regional lymphadenopathy, suggestive of advanced appendiceal malignancy. Surgical exploration identified a mucin-producing appendiceal tumor with metastatic involvement of the mesentery, liver, and lymph nodes. Histopathological examination confirmed an invasive, moderately differentiated mucinous adenocarcinoma of the appendix, without lymphovascular or perineural invasion. The mesenteric lesion showed malignant neoplastic cells consistent with metastatic appendiceal adenocarcinoma, infiltrating the surrounding tissue. The patient underwent surgical resection followed by systemic chemotherapy. During follow-up, clinical evolution was consistent with advanced metastatic disease requiring ongoing multidisciplinary management. This case highlights the diagnostic and therapeutic challenges of advanced appendiceal mucinous adenocarcinoma and emphasizes the importance of complete pathological characterization and coordinated oncologic care.