SolidPseudopapillary Tumour (SPPT)

AKA Papillary and Solid Epithelial Neoplasm,Papillary-Cystic Neoplasm, Cystic-Solid Papillary Carcinoma

Epidemiology:

• Young women typically (child-bearing age)
• F:M 9:1
• average age 30y but all age groups
• rare in first decade

Common sites:

Gross features:

• large (average 10cm)
• areas of hemorrhage and necrosis
• encapsulated usually
• cystic sometimes
• rarely causes obstruction

Histologic features:

• cellular, appears somewhat like endocrine neoplasm
• pseudopapillae covered by several layers of epithelial cells
• thick fibrovascular core
• mucinous changes around fibrovascular core often (important)
• nuclei ovoid, folded
• relatively uniform
• longitudinal groove typically
• indistinct nucleoli
• few mitoses
• cytoplasmic hyaline globules typically
• collections of foamy cells may be present
• hemorrhages
• necrotic foci
• malignant features (uncommon)
• mets
• perineural invasion
• venous invasion
• lymphatic invasion
• atypia
• mitoses
• not graded

Immunophenotype:

Marker:	Sensitivity:	Specificity:
Vimentin	“consistent”
CD10	"consistent"
CD56	“consistent”
Beta-catenin (nuclear)	“consistent”
Alpha-1-antitrypsin	“consistent
Keratin	<50%
Desmoplakin
Trypsin
Alpha-1-antichymotrypsin	maybe
Amylase
Synaptophysin	“occasional”
PR	“often”
Chromogranin (neg)	“always”
Acinar and ductal markers (neg)	“consistently”
ER (neg)	“typically”
Inhibin (neg)
CEA (neg)		Acinar CA is positive typically

Molecular features:

•  Beta-catenin mutations almost always

Other features:

• EM – large electon-dense granules
• Containing complex internal membranous and granular inclusions
• Contain alpha-1-antitrypsin immunohistochemically
• palpable abdominal mass is most common presentation
• thought to have capacity for dual (exocrine and endocrine) differentiation, but predominantly exocrine
• uncertain differentiation
• prognosis excellent but has metastasized
• metastasis in 10-15% of cases (liver or peritoneum)
• lymph node mets are rare
• even with mets, survival is good

References:

· Odze;Surgical Pathology of the GI Tract, 2004