This document discusses updates to the classification of thyroid neoplasms in the latest WHO classification. It describes the hierarchical classification system used which is based on cell of origin, pathologic features, molecular characteristics, and biological behavior. It provides details on the classification of benign and malignant follicular cell-derived neoplasms. It introduces new entities such as noninvasive encapsulated follicular variant of papillary thyroid carcinoma (NIFTP) and differentiated high-grade thyroid carcinoma (DHGTC). It also discusses criteria for diagnosing poorly differentiated thyroid carcinoma and provides recommendations for management and follow-up of thyroid neoplasms based on risk stratification.

1. THYROID NEOPLASMS- AN UPDATE
Dr Vivekanand A
Assistant Professor
Department of ENT
KARUNA MEDICAL COLLEGE,
Palakkad

3. • In the fifth edition, each tumor is listed
within a hierarchical taxonomic
classification based on
• the cell of origin,
• pathologic,
• molecular features,
• biological behavior

4. 1. Development abnormalities
2. Follicular cell-derived neoplasms
3. Thyroid C-cell-derived carcinoma
4. Mixed medullary and follicular cell-
derived carcinomas
5. Salivary gland-type carcinomas of
the thyroid
6. Thyroid tumors of uncertain
histogenesis
7. Thymic tumors within the thyroid
8. Embryonal thyroid neoplasms

5. Follicular cell-
derived neoplasms
Benign tumors
Low risk
neoplasms
Malignant
neoplasms
Based on biological
behavior

6. Common thyroid histopathological diagnosis
clinicians encounter
• adenomatous / adenomatoid
hyperplasia / nodule,
• colloid goiter,
• simple goiter,
• colloid / hyperplastic nodule
• Multinodular
•

7. • Multinodular goiter: irregular
enlargement of thyroid gland due to
repeated episodes of hyperplasia
and involution (degeneration) of
simple goiter
• Nodules are clonal or polyclonal and
are due to heterogeneous responses
of follicular epithelium to TSH

8. Therefore, an
umbrella term of
‘follicular nodular
disease’ (FND) has
been proposed in
the latest WHO
classification
BENIGN TUMORS
1. Thyroid follicular nodular disease
2. Follicular thyroid adenoma
3. Follicular thyroid adenoma with papillary architecture
4. Oncocytic adenoma of the thyroid

9. Benign tumors
Thyroid follicular nodular disease
Follicular thyroid adenoma
Follicular thyroid adenoma with papillary architecture
Oncocytic adenoma of the thyroid

11. FOLLICULAR ADENOMA WITH
PAPILLARY ARCHITECTURE

12. Oncocytic adenoma

13. Low-risk follicular cell-derived thyroid
neoplasms

14. NIFTP FT-UMP
WD-UMP HTT

15. Noninvasive encapsulated follicular
variant of papillary thyroid carcinoma
• Pathologic diagnostic criteria:Inclusion criteria
• Major features:
• Encapsulation or clear demarcation
• Follicular growth pattern with less than 1% papillae (see comment below)
• If solid, trabecular or insular patterns seen; these in total should be less than 30% of the total tumor volume
• No psammoma bodies
• Nuclear features of papillary thyroid carcinoma (enlargement, crowding / overlapping, elongation, irregular contours, grooves, pseudoinclusions,
chromatin clearing), nuclear score should be 2 or 3
• Minor features:
• Dark colloid
• Irregularly shaped follicle
• "Sprinkling sign"
• Follicles cleft from stroma
• Multinucleated giant cells within follicles
• Exclusion criteria:
• Any capsular or vascular invasion but if the whole capsule has not been examined thoroughly then the default diagnosis is still
noninvasive encapsulated FVPTC (EFVPTC) and it is NOT a NIFTP
• True papillary structures in more than 1% of tumor volume, psammoma bodies, infiltrative border
• Tumor necrosis (not associated with FNA), increased mitoses (defined as at least 3 per 10 HPF)
• Cell / morphological characteristics of any other papillary thyroid carcinoma variant (e.g., tall cell, columnar cell, cribriform morular,
diffuse sclerosing, etc.) or oncocytic lesion

16. Follicular tumor – uncertain malignant potential
(FTUMP) and well differentiated tumor uncertain
malignant potential
• Thyroid tumors of uncertain malignant potential are rare lesions in
which histological confirmation of capsular and/or vascular invasion is
equivocal.
• These tumor entities require extensive microscopic assessment of the
entire capsule/tumor interface, as a single focus of invasive focus
would disqualify these diagnoses.

17. NIFTP

18. HYALINISING TRABECULAR TUMOR
• HTTs are follicular cell-derived thyroid neoplasms with PTC-related
nuclear atypia, trabecular growth pattern, extracellular hyaline matrix
and specific PAX8::GLIS1 and PAX8::GLIS3 fusions.
• Metastases associated with HTT have only been reported in single,
historic cases.

19. MALIGNANT
TUMOR
• Follicular thyroid carcinoma
• Invasive encapsulated follicular variant papillary
thyroid carcinoma
• Papillary thyroid carcinoma
• Oncocytic carcinoma of the thyroid
• Follicular-derived carcinomas, high-grade
 Poorly differentiated thyroid carcinoma
 Differentiated high-grade thyroid carcinoma
• Anaplastic follicular cell-derived thyroid carcinoma

20. POORLY DIFFERENTIATED THYROID
CARCINOMA
• Turin consensus diagnostic criteria:
• Solid / trabecular / insular growth pattern
• No nuclear features of papillary carcinoma
• Presence of at least one of following: convoluted nuclei, ≥ 3 mitotic figures/10 HPF,
tumor necrosis
• Other:
• Prototypical type insular carcinoma: solid nests (may contain microfollicules) composed of small
uniform cell with round hyperchromatic nuclei or convoluted nuclei, increased mitotic figures,
necrosis
• Others tumors: solid nests composed of larger more pleomorphic tumor cells; may have
oncocytic cells, clear cells, signet ring cells or rhabdoid cells
• Component of well differentiated tumor (papillary or follicular carcinoma) may also be present
• As few as 10% of poorly differentiated carcinomas (in otherwise well differentiated carcinomas)
may be associated with unfavorable prognosis
• May have peritheliomatous pattern (tumor cells around blood vessels with necrosis of tumor
cells further away from vessels), vascular and capsular invasion

22. • However, some experts have considered a mitotic index ≥5 mitoses
per 2 mm2 (10 high-power fields) and/or tumor necrosis as
indications of a poorly differentiated phenotype even in the absence
of morphologic dedifferentiation .
• In the fifth edition of the WHO classification, an intermediate entity
of ‘differentiated high-grade thyroid carcinoma’ (DHGTC) is therefore
introduced for PTCs and FTCs/OTCs with ≥5 mitoses per 2
mm2 and/or tumor necrosis to highlight high-risk differentiated
thyroid carcinomas (Baloch et al. 2022).
• The tumors classified as such may have retained PTC-related nuclear
atypia or a follicular growth pattern and features that are not
acceptable for a PDTC diagnosis (Fig. 3

23. NIFTP

24. Benign entity?

25. ATA guidelines risk
stratification
• Based on ERR
• Low risk
• ERR of less than 1%

26. How to manage

27. Risk Stratification

30. TSH suppression- How much???
Low risk-
maintain normal
range
Intermediate –
0.1- 0.5
High risk- <0.1

33. TAKE HOME MESSAGE
Lobectomy/Hemi
thyroidectomy is
adequate
Close follow up-
clinical/radiological
Maintain TSH-
normal range