Hyalinizing trabecular adenoma
Sorry, that is
The correct diagnosis is:
Papillary carcinoma, follicular variant
- Smears are cellular containing numerous variably cohesive follicular epithelial cells in trabecular and microfollicular patterns.
- Rare follicular epithelial cells reveal well defined intra-nuclear inclusions. Pap-stained smears (not available with this case) are more helpful in identifying powdery chromatin and nuclear grooves.
- There is a small amount of dense colloid.
- The biopsy reveals a single focus of papillary carcinoma, mixed conventional and follicular type. The cytologic and histologic diagnosis both rest on nuclear features (powdery chromatin, intranuclear inclusions, and nuclear grooves) with follicle formation suggesting the follicular variant. If the nuclear features are poorly developed the diagnosis may not be possible.
- The follicular variant of papillary thyroid carcinoma is a common morphologic subtype, and has a similar clinical and pathological behaviour to pure papillary carcinoma. Aspirates are often interpreted as follicular neoplasm (adenoma or minimally invasive follicular carcinoma) or suspicious for papillary carcinoma rather than malignant. Since there are important differences in biologic behaviour and management, accurate diagnosis is important.
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Zidan J, Karen D, Stein M, Rosenblatt E, Basher W, Kuten A. Pure versus follicular variant of papillary thyroid carcinoma: clinical features, prognostic factors, treatment, and survival. Cancer 2003;97:1181-5.
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