## Why Papillary thyroid carcinoma is right Psammoma bodies (marked **A**) are concentric lamellated calcifications with an onion-skin appearance that represent calcified tumor cell debris. They are a HALLMARK finding in papillary thyroid carcinoma (PTC), the most common thyroid malignancy (80% of all thyroid cancers). The presence of psammoma bodies on FNA cytology is highly suggestive of PTC, especially when accompanied by characteristic nuclear features such as "orphan-eye" nuclei (clear, empty appearance from chromatin margination), nuclear grooves, and pseudoinclusions. PTC has an excellent prognosis (>95% 10-year survival) and typically spreads via lymphatic routes to cervical lymph nodes. The diagnosis is confirmed by histology showing papillary architecture with these characteristic features. (Robbins 10e Ch 24; Harrison 21e Ch 384) ## Why each distractor is wrong - **Follicular thyroid carcinoma**: Follicular carcinoma lacks psammoma bodies and does not show the characteristic nuclear features of PTC. It is defined by capsular and vascular invasion rather than architectural pattern, and has a less favorable prognosis than PTC. - **Medullary thyroid carcinoma**: This arises from parafollicular C cells and is associated with calcitonin production and amyloid deposition, NOT psammoma bodies. It is part of MEN 2 syndrome in some cases and has a worse prognosis than PTC. - **Anaplastic thyroid carcinoma**: This is a highly aggressive, undifferentiated malignancy with poor prognosis. It does not show psammoma bodies or the characteristic nuclear features of PTC. It typically occurs in elderly patients and is rapidly fatal. **High-Yield:** PSaMMoma bodies = Papillary thyroid carcinoma (most common), Serous ovarian carcinoma, Meningioma, Mesothelioma — memorize this mnemonic for NEET PG. [cite: Robbins 10e Ch 24; Harrison 21e Ch 384]
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