Solid-pseudopapillary Neoplasm of the Pancreas

Definition

Bland low grade malignant neoplasm characterized by solid and discohesive pseudopapillary areas

Variably solid, pseudopapillary and cystic pattern
- Occasionally completely solid
  - Usually smaller tumors
  - May be sclerotic
  - May have foamy macrophages and cholesterol clefts
- Frequent pseudopapillary pattern
  - Formed by separation of vascular cores with adherent cells
    - Typically thin walled vessels in cores
  - Spaces may be acellular or contain RBCs (blood lakes)
- Frequent cystic pattern
  - Degenerative changes may cause predominantly cystic structure
Uniform polygonal cells
- Cytoplasm clear to eosinophilic
  - Lack glycogen and mucin
  - May have intra or extracytoplasmic PASd+ globules
- Bland round to oval nuclei
  - Mitotic figures rare
  - Frequent longitudinal nuclear grooves
- Frequently radially oriented around vessels
  - May resemble rosettes
Features proposed as predictive of malignant behavior
- Perineural invasion
- Vascular invasion
- Deep invasion of pancreatic parenchyma
- Invasion of surrounding organs
- Nuclear atypia
- Elevated mitotic rate
- It is not clear if any of these are statistically significant predictors
- Rare tumors lacking these features may still metastasize
Rare anaplastic transformation has been reported
- Very high mitotic rate, necrosis, atypia and high nuclear:cytoplasmic ratio

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting / last update: 2/10/07, 7/14/11, 1/4/12