Thyroid & parathyroid

Other common thyroid carcinomas

Poorly differentiated thyroid carcinoma

Last author update: 1 November 2017
Last staff update: 5 May 2023 (update in progress)

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PubMed Search: Poorly differentiated carcinoma [title] thyroid

Shuanzeng (Sam) Wei, M.D., Ph.D.
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Cite this page: Wei S. Poorly differentiated thyroid carcinoma. website. Accessed June 1st, 2023.
Definition / general
Essential features
  • Intermediate grade follicular cell carcinoma with limited evidence of follicular cell differentiation
  • Insular / trabecular carcinoma
  • Primordial cell carcinoma
  • Poorly differentiated follicular carcinoma
  • Poorly differentiated papillary carcinoma
  • Solid type follicular carcinoma
  • High risk thyroid carcinoma of follicular cell origin
ICD coding
  • ICD-10: C73 - malignant neoplasm of thyroid gland
  • Older patients, mean age 55 - 63 years
  • 0.3 - 6.7% of thyroid carcinomas
  • More common in Europe and South America than U.S. (Mod Pathol 2010;23:1269)
  • Iodine deficiency may be a risk factor; no association with radiation exposure (Clin Oncol (R Coll Radiol) 2011;23:261)
  • Some tumors are de novo; some arise from dedifferentiation of follicular or papillary carcinoma
Clinical features
  • Large solitary thyroid mass. Patient may have a history of recent growth in a longstanding uninodular or multinodular thyroid (Am J Surg Pathol 1984;8:655)
  • Intermediate behavior between well differentiated and anaplastic carcinoma (World J Surg 2007;31:934)
  • Has nodal and hematogenous metastases and 3 year survival of 38% (Langenbecks Arch Surg 2007;392:671)
  • Extends to perithyroidal soft tissue in 60 - 70% cases
  • Vascular invasion in 60 - 90% cases
  • Regional lymph node metastasis in 15 - 65%
  • Distant metastasis in 40 - 70%
Radiology description
  • Ultrasound shows inhomogeneous hyoechoic mass (Cancer 2006;106:1286)
  • Cold on scintigraphy and positive on FDG PET
Prognostic factors
Case reports
  • Total thyroidectomy, neck dissection, radioactive iodine and suppressive thyroxine
Gross description
  • Large (median size: 5 cm), grayish white, some show soft pale areas of necrosis
  • Pushing margins, may be partially encapsulated
  • Can have satellite nodules (Am J Surg Pathol 1984;8:655)
Gross images

Contributed by Mark R. Wick, M.D. and AFIP images

Various images

Poorly differentiated thyroid carcinoma

Massive cervical lymph node metastasis

Images hosted on other servers:

A well demarcated tumor

Tumor with invasive growth pattern

Microscopic (histologic) description
  • 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 (Am J Surg Pathol 2007;31:1256)
  • 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 (Am J Surg Pathol 1984;8:655)
      • 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 (Am J Surg Pathol 2011;35:1866)
      • May have peritheliomatous pattern (tumor cells around blood vessels with necrosis of tumor cells further away from vessels), vascular and capsular invasion (Lloyd: WHO Classification of Tumours of Endocrine Organs, 4th Edition, 2017)
Microscopic (histologic) images

Contributed by Shuanzeng Wei, M.D., Ph.D., Andrey Bychkov, M.D., Ph.D.

Nests of tumor with necrosis

Follicular carcinoma with high grade progression

Case #435

Various images

Cytology description
  • Highly cellular, crowded cell clusters with solid, trabecular or insular morphology (Cancer 2009;117:185, Cytopathology 2016;27:176)
  • Background of single cells with high N:C ratio
  • May have necrotic background and increased mitotic figures
Cytology images

Contributed by Ayana Suzuki, C.T. and Shuanzeng Wei, M.D., Ph.D.

Insular pattern

Diff-Quik and Pap stains (100x)

Diff-Quik and Pap stains (400x)

Corresponding histology shows mitosis and necrosis

Images hosted on other servers:

Fig. 5: nesting pattern of cells

Fig. 1: overlapping cells with round, regular nuclei

Fig. 2: large clusters and single cells

Fig. 3: cellular nests of loosely cohesive cells

Fig. 7: overlapping cells with mild atypia

Fig. 4: small microfollicle of tumor cells

Fig. 6: vacuolated cytoplasm with round nuclei

Negative stains
Molecular / cytogenetics description

Poorly differentiated thyroid carcinoma by M. Brandwein (2020)

Differential diagnosis
Board review style question #1
Which of the following features are not required for the diagnosis of poorly differentiated thyroid carcinoma?

  1. Absence of conventional nuclear features of papillary thyroid carcinoma
  2. Necrosis / convoluted nuclei / increased mitotic activity
  3. Solid, trabecular or insular growth
  4. Vascular invasion
Board review style answer #1
D. Vascular invasion. The Turin criteria specify solid / trabecular / insular growth, lack of conventional nuclear features of papillary thyroid carcinoma and one of the following: necrosis, convoluted nuclei or increased mitotic activity (3 or more mitoses/10 HPF). Vascular invasion may be seen in a variety of thyroid carcinomas and is an adverse prognostic factor regardless of histologic subtype or grade.

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Reference: Poorly differentiated thyroid carcinoma
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