Various facets of low-grade appendiceal mucinous neoplasms (LAMNs)

Abstract

Low-grade appendiceal mucinous neoplasms are rare tumors of the appendix that affect women and men equally from the fifth decade of life. They are characterized by the replacement of normal appendiceal mucosal tissue with villous proliferations of mucinous epithelium. The tumor cells secrete mucin, which accumulates in intracytoplasmic vacuoles. Tumor growth occurs by pushing mechanisms without invasion, invasion defining adenocarcinomas. In the early stages, these tumors have low risk of recurrence and are not life-threatening, appendectomy being sufficient for cure. Sometimes, the accumulation of mucin produces ruptures of the appendiceal wall, which may seed tumor content outside the appendix, complicating diagnosis and prognosis, presenting a high risk of recurrence and, in the case of pseudomyxoma peritonei, becoming disabling and life-threatening. For these, treatment becomes more complex, with decreased survival rate.