Types of Pancreatic Masses
Pancreatic masses are broadly categorized into solid and cystic lesions, with solid masses predominantly being pancreatic ductal adenocarcinoma (~80% of all pancreatic cancers), while cystic lesions include both neoplastic and non-neoplastic entities that require careful differentiation due to varying malignant potential. 1
Solid Pancreatic Masses
Malignant Solid Masses
Exocrine Tumors:
- Pancreatic ductal adenocarcinoma (PDAC) accounts for approximately 80% of all pancreatic cancers and ~95% arise from the exocrine portion of the pancreas 1
- Adenosquamous carcinoma and undifferentiated carcinomas with osteoclast-like giant cells are associated with poorer prognosis compared to standard PDAC 1
- Acinar cell carcinomas have a slightly better prognosis than PDAC 1
- Colloid (mucinous noncystic) carcinoma is characterized by mucin-producing epithelial cells suspended in extracellular mucin pools 1
- Medullary carcinoma shows poor differentiation with syncytial growth pattern and pushing borders 1
Neuroendocrine Tumors:
- Pancreatic neuroendocrine tumors (PNETs) are the second most frequent pancreatic cancers after adenocarcinoma 1
- These have distinct clinical behavior and management compared to exocrine tumors 1
Benign Solid Masses
Only 2% of tumors of the exocrine pancreas are benign 1
Cystic Pancreatic Masses
Cystic neoplasms represent 10-15% of cystic lesions of the pancreas 1
Epithelial Neoplastic Cystic Lesions (Malignant Potential)
Major Mucinous Lesions (Require Surveillance/Intervention):
- Intraductal papillary mucinous neoplasm (IPMN) - all types have malignant potential and are characterized by dilated main pancreatic duct and/or side branches with mucus-secreting cells 1, 2
- Mucinous cystic neoplasm (MCN) - can be cystadenoma or cystadenocarcinoma with potential for malignant progression 1
- Cystic ductal adenocarcinoma - represents malignant transformation or cystic degeneration of adenocarcinoma 1, 3
Non-Mucinous Neoplastic Lesions:
- Serous cystic neoplasm (SCN)/serous cystadenoma - typically benign with no malignant potential 1
- Serous cystadenocarcinoma - rare malignant variant 1
Other Neoplastic Cystic Lesions:
- Solid pseudopapillary neoplasm - rare, low malignant potential, usually in body/tail 1, 2
- Cystic neuroendocrine tumor G1-2 1
- Acinar cell cystadenoma and cystic acinar cell carcinoma 1
- Cystic hamartoma, cystic teratoma (dermoid cyst), cystic pancreatoblastoma 1
- Accessory-splenic epidermoid cyst 1
- Cystic metastatic epithelial neoplasm 1
Epithelial Non-Neoplastic Cystic Lesions (No Malignant Potential)
- Pancreatitis-associated pseudocyst - most common cystic lesion, resulting from autodigestive tissue necrosis in acute pancreatitis 1, 4
- Lymphoepithelial cyst 1
- Mucinous non-neoplastic cyst 1
- Retention cyst/dysontogenetic cyst 1
- Enterogenous cyst, peri-ampullary duodenal wall cyst, endometrial cyst 1
- Congenital cyst (in malformation syndromes) 1
- Parasitic cyst 1
Non-Epithelial Cystic Lesions
Neoplastic:
- Benign non-epithelial neoplasms (e.g., lymphangioma) 1
- Malignant non-epithelial neoplasms (e.g., sarcomas) 1
Critical Clinical Distinctions
The most important clinical distinction is between mucinous and non-mucinous cystic lesions, as mucinous lesions (IPMN and MCN) have malignant potential and require surveillance or resection, while non-mucinous lesions (serous cystadenoma) are benign. 1
Common Pitfall: Pancreatic neoplasms can undergo cystic degeneration, causing extensively degenerated solid tumors to mimic benign cystic lesions on imaging, complicating radiological diagnosis 3. Pseudocysts remain a diagnosis of exclusion, as inflammatory smears without epithelial cells are nonspecific and similar patterns may occur when cystic neoplasms undergo degenerative changes 5.
Precursor Lesions
The most frequent precursor lesions for pancreatic cancer are: