Follicular
Carcinoma
Common sites:
Gross features:
- solitary nodule
- may be well
circumscribed or widely infiltrative
- gray to tan to pink
- sometimes central
fibrosis or foci of calcification
Histologic features:
- distinction from adenoma
requires presence of capsular and/or vascular invasion
- vascular invasion
must involve capsular or extra-capsular vessels
- capsule is usually
thicker than in adenoma
- most contain fairly
uniform cells forming small follicles containing colloid
- some contain nests
or sheets of cells without colloid
- lacking the nuclear
features diagnostic of papillary carcinoma
- no psammoma bodies
- Hurthle
cell variant:
- Dominated by cells
with an abundant granular, eosinophilic cytoplasm
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Molecular features:
- RAS family mutations (50%)
- T(2;3)(q13;p25) translocation (33%) (mutually
exclusive from RAS mutations)
- PAX8- PPAR-gamma-1 gene fusion
- <10% of
adenomas also harbour this fusion transcript
Other features:
- Robbins &
Cotran Pathologic Basis of Disease (2005)