WHO 2022 Thyroid betehesda pathology new

WHO

1. UPDATES FROM 2022 WHO CLASSIFICATION OF THYROID TUMORS BY:DR.ANISH TINA First year pathology

2. 2022 WHO CLASSIFICATION -THYROID TERMINOLOGY Variant - SUBTYPE Hurthle cell - ONCOCYTIC CELL Gene fusion (-)(/ )to(::) eg:ETV6::NRTK3 NEW ENTITIES Follicular Nodular Disease(FND) High grade Follicular cell derived carcinoms Thyroblastoma Mitosis - 2 millimeter square

3. Follicular cell derived neoplasm- BENIGN, LOW RISK, MALIGNANT BENIGN : FND -Multifocal hyperplastic/neoplastic lesions that occur in MNG Follicular adenoma - RAS mutation Follicular adenoma with papillary architecture (TOXIC ADENOMA) Mutations- TSHR,GNAS,EZH1 Oncocytic adenomas

4. Grossly thyroid gland enlarged with var iable sized multiple nodules Spectrum of morphological seen: Small colloid rich nodules with Sanderson’s polsters to Large poorly defined colloid rich macrofollicular nodules. Multiple,encapsulated,more well defined Some are monoclonal ,some are polyclonal No correlation between clonality and morphology

5. Follicular adenoma with papillary architecture

6. LOW RISK : Borderline tumors NIFTP :Non Invasive Follicular Thyroid neoplasm with Papillary like nuclear features. <1%true papillae Absence of BRAFV600E mutation. MITOTIC ACTIVITY: <3 mitosis -NIFTP 3-4mitosis -Encapsulated PTC with predominantly follicular growth >5 mitosis - Non invasive high grade folicular variant of PTC(DHGTC) Subcentimeter NIFTP Oncocytic NIFTP : >75%oncocytic cells.

7. NIFTP

8. Follicular tumors of uncertain malignant potential (?invasion) Follicular tumor of UMP - Lacks PTC like nuclear features (Score 0-1) Well differentiated tumor of UMP - more or less PTC (score 2-3) Hyalinizing Trabecular Tumor(HTT)

9. MALIGNANT: PAPILLARY THYROID CARCINOMA Diagnosis:Nuclear features,papillary growth pattern,Invasive features. Papillary thyroid Microcarcinoma - No longer a variant of PTC PTC -microcarcinoma - Also to be further histologically subtyped . Encapsulated variant -Encapsulated classic subtype of PTC. Follicular variant of PTC: Infiltrative,Encapsulated with invasion,macrofollicuilar and diffuse or multinodular follicular subtyp “Macrofollicular & Diffuse or multinodular fillicular subtype - NOT Mentioned”

10. Infiltrative - Classic PTC without papillae -BRAF LIKE TUMOR (Infiltrative tumors with florid nuclear atypia) Encapsulated with invasion - resembles FTC - RAS like tumor(Expansile pattern of growth with subtle or less nuclear arypia) Invasive Encapsulated Follicular variant of PTC- IEFVPTC FTC and FVPTC to be differentiated entirely on nuclear morphology.(FTC lacks nuclear features). Non invasive encapsulated follicular PTC - NIFTP (Low risk) FTC & FVPTC - based on degree of invasion further subtyped: minimally invasive- CAPSULAR invasion angioinvasive- into blood vessels (limited -<4 foci;extensive -4 or more foci) widely invasive

11. Aggressive PTC - Tall cell, Columnar cell, Hobnail PTC Tall cell PTC - CRITERIA : 3 times taller than width 30% of tall cells HOBNAIL PTC: mixed papillary and micropapillary structure with dyscohesive tumor cells. More pronounced NUCLEAR ATYPIA than classic PTC’S. HOBNAIL LIKE MORPHOLOGY : Found in >30% of PTC.Encapsulated or well cicumscribed Classic PTC’S showing CYSTIC CHANGES and have EDEMATOUS HYALINISED papillae lined by hobnailing tumor cells. Considered as Degenerative atypia, lower rate of Aggressiveness & better prognosis.

12. Cribriform Morular variant of PTC- NO longer subtype of PTC. Listed under TUMOR OF UNCERTAIN HISTIOGENESIS.

13. ONCOCYTIC CARCINOMA: Considered as distinct entity Refered to as Oncocytic follicular cell derived neoplasms(more than 75%oncocytic cells) Lacks characteristic nuclear features of PTC.If with nuclear features it is called as Oncocytic PTC LACKS High grade features - necrosis and more than or equal to 5 mitosis/mm2

14. PDTC - Poorly Differentiated Thyroid Carcinoma FTC- has solid or trabecular growth with more than or equal to 3 mitosios– PDTC DHGTC-Differentiated high grade thyroid carcinoma FTC without solid or trabecular growth with more thamn or equal to 5 mitosis. Follicular derived carcinomas -HIGH GRADE

15. Anaplastic carcinoma of thyroid Primary squamous cell carcinoma of thyroid previously considered a separate entity is now histologic pattern of ATC. ATC with squamous cell carinoma: More BRAFV600E mutations and PAX8 positivity Intrathyroidal thymic carcinoma mimic ATC with SCC pattern

16. Medullar carcinoma thyroid Histologic Grading for high grade: MITOTIC COUNT - more than or equal to 5 mitosis TUMOR NECROSIS- present Ki67 proliferative index-more than or equal to 5% Benefit high grade patients in closer follow up and careful monitoring for distant metastatis.

17. Salivary gland type carcinoma of thyroid Mucoepidermoid carcinoma Secretory carcinoma of salivary gland type SCLEROSING MUCOEPIDERMOID CARCINOMA(SMECE) - reclassified as Thyroidtumors of uncertain histiogenesis Reason: Fusion genes hallmark of salivary gland :ETV6::NTRK3,CRTC3::MAML2 are not found in SMECE. lack of common mutations -BRAF,RAS Presumed to arise from solid cell nests MET hyperploidy,APC,NTRK3,NF1

18. TUMORS OF UNCERTAIN HISITIOGENESIS Cribriform morular variant of thyroid carcinoma -previously distinct variant of PTC because of papillary pattern and nuclear features. Different molecular profile - Wnt/beta -catenin pathway No BRAF mutations Negative for thyroglobulin,PAX8 cribriform component- TTF1 positive,morulae are negative

19. THYROBLASTOMA Rare embryon ic high grade thyroid neoplasm composed of primitive follicular cells,Small cell and mesenchymal stroma DICER1 Mutation New term for Malignant teratoma and carcinosarcoma associated with DICER1 mutations in thyroid gland.

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