Table 4.

Summary of the different subtypes of pancreatic ductal adenocarcinoma[52]

Morphological Variant	Characteristics
Adenosquamous carcinoma	Significant components of ductal/glandular and squamous differentiation (at least 30%). Considered to have a worse prognosis than pancreatic adenocarcinoma.
Colloid/mucinous carcinoma	Production of copious amounts of extracellular stromal mucin. Most arise in association with intraductal papillary mucinous neoplasms; thought to have more favourable prognosis than pancreatic adenocarcinoma
Undifferentiated/anaplastic carcinoma	Minimal or no differentiation; highly atypical cells which may appear spindle shaped or sarcomatoid, often admixed with osteoclast-like giant cells. One of the most aggressive forms of pancreatic cancer with extremely poor survival rates
Signet ring cell carcinoma	Discohesive, singly invasive cells with intracytoplasmic mucin that may displace the nucleus. Similar tumours throughout the gastrointestinal tract. Very rare form of pancreatic cancer with prognosis similar to that of pancreatic adenocarcinoma
Medullary carcinoma	Syncytial arrangement of pleomorphic epithelial cells with associated intratumoral lymphoid infiltrate. Prognosis is slightly better than pancreatic adenocarcinoma
Hepatoid carcinoma	Morphological similarity to hepatocellular carcinoma. May produce bile. Very rare tumour with a poor prognosis similar to that of pancreatic adenocarcinoma