Combined appendiceal goblet cell adenocarcinoma and low grade appendiceal mucinous neoplasm: a case report

Abstract

Appendiceal goblet cell adenocarcinomas (GCA) are rare entities with a distinctive composition of goblet, paneth and neuroendocrine cells. Cases of combined or collision GCAs and other appendiceal tumours exist in the literature, with only a few publications describing combined GCA and low-grade mucinous neoplasm (LAMN). A 73-year-old female underwent a right hemicolectomy following an appendiceal orifice polypectomy showing adenocarcinoma. Histological examination revealed combined GCA and LAMN at the orifice, and LAMN in the remaining appendiceal mucosa. By immunohistochemistry, the GCA showed CK20, synaptophysin and chromogranin reactivity. Grading was performed using the WHO-recommended three-tiered system based on the proportion of low and high-grade morphological features. Current views of GCA and appendiceal neoplasm biology revolve around the unitary hypothesis of neoplasia arising from a pluripotent progenitor cell. This is supported by the observation of varied morphological components at primary and metastatic disease sites, and shared expression of several differentiation markers among appendiceal neoplasms. Genomic studies have shown that appendiceal neoplasms acquire different mutations during tumourigenesis culminating in entities with distinct mutational profiles. Prospective studies into GCA-specific optimal treatment regimens are lacking, and current treatment strategies have been extrapolated from those of appendiceal and colon adenocarcinomas, despite having different pathological molecular signatures.