Patients with low-grade appendiceal mucinous carcinomas (LAMN) treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) have a favorable prognosis. A subgroup presents a clinically aggressive course with disease progress despite any treatment. The purpose of the study is to report the experience with clinically aggressive LAMN patients treated by the same team and review the literature. Four patients with clinically aggressive LAMN were reviewed. Clinical and histopathological characteristics were re-examined. Recurrences and the time of recurrence, as well as the survival time, were recorded. There were 4 men with clinically aggressive LAMN treated with CRS plus HIPEC. One of them underwent CC-0 surgery, two underwent CC-1, and one CC-3 surgery. All received systemic chemotherapy after surgery. Recurrence was recorded in 3 patients in 4-23 months after initial treatment. Two of them underwent secondary CRS. Three patients died of disease recurrence in 13-23 months, and one is alive with disease relapse 49 months after initial surgery. LAMN was identified in both initial specimens and in specimens of reoperation. The prognosis of LAMN patients treated with CRS plus HIPEC is favorable. A small number of them presents clinically aggressive course unresponsive to any treatment. Molecular and genetic studies are required to identify this group of LAMN patients who have an unfavorable prognosis.