Diagnosis and Discussion

Diagnosis

Low-grade appendiceal mucinous neoplasm (LAMN)

Discussion

The macroscopic and microscopic features are consistent with the diagnosis of low-grade appendiceal mucinous neoplasm (LAMN)¹. Primary tumors of the appendix are relatively rare. Mucinous tumors are often identified by the build-up of gelatinous mucin within the lumen of the appendix, which is not infrequently the result of neoplastic adenomatous growth of the appendiceal epithelium². LAMNs are characterized histologically by loss of the normal lamina propria and presence of low-grade mucinous epithelium. Often they exhibit mural calcifications and fibrosis¹.

While LAMNs are low-grade and do not meet the histologic criteria of an invasive adenocarcinoma, they still have the potential to spread outside of the appendix. This can result in the clinically significant complication known as pseudomyxoma peritonei in which mucin-secreting cells spread to the peritoneal cavity, pelvis, liver capsule, or omentum¹. Thus, the identification and notation of cellular or acellular mucin extending into or through the appendiceal wall is important. LAMNs are often identified incidentally, as they can often be asymptomatic. When they do present with symptoms they often include abdominal pain, a palpable mass, or acute appendicitis².

References:

1. Carr N, et al. The histopathological classification, diagnosis and differential diagnosis of mucinous appendiceal neoplasms, appendiceal adenocarcinomas and pseudomyxoma peritonei. Histopathology. 2017.

2. Tirumani SH, et al. Mucinous neoplasms of the appendix: a current comprehensive clinicopathologic and imaging review. Cancer Imaging. 2013.

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