Pathology Features of Gallbladder Carcinoma

Gallbladder carcinoma (GBC) is the most common biliary tract carcinoma. The main etiological association is with gallstones. The most common subtype is the biliary-type adenocarcinoma. The fundus of the gallbladder is the most affected site. The usual appearance is a diffuse, flat, extensive, firm, white thickening of the wall with diffuse growth. Inflammation appears to be the main event in carcinogenesis, with more than 50% harboring TP53 alterations. They display usually tubular architecture lined with cubic to columnar cells with varying degrees of pleomorphism. Its morphology and behavior are similar to pancreatic ductal adenocarcinoma. Intestinal-type gallbladder adenocarcinoma resembles colonic adenocarcinoma, and it is necessary to rule out metastasis from colonic adenocarcinoma. Micropapillary, poorly cohesive, adenosquamous, pure squamous, undifferentiated, and sarcomatoid are other rare subtypes of GBC. Neuroendocrine neoplasms (NENs) are divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated, large- and small-cell neuroendocrine carcinomas (NECs). Mixed neuroendocrine-non-neuroendocrine neoplasia (MiNEN) occurs in more than one-third of NECs and is described as heterogeneous malignancies characterized by histologically recognizable neuroendocrine and exocrine, each composing ≥30% of the neoplasm volume.