Thyroid gland
Other carcinoma
Poorly differentiated thyroid carcinoma

Topic Completed: 1 November 2017

Revised: 15 March 2019

Copyright: 2002-2018,, Inc.

PubMed Search: (Poorly differentiated carcinoma [title]) thyroid

Related Topic: Poorly differentiated carcinoma with rhabdoid features

Shuanzeng Wei, M.D., Ph.D.
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Cite this page: Wei S. Poorly differentiated thyroid carcinoma. website. Accessed July 18th, 2019.
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
  • 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

Images hosted on PathOut server:

AFIP image

Massive cervical lymph node metastasis (AFIP)

Images contributed by Dr. Mark R. Wick:

Various images

Images hosted on other servers:

Fig 1 - 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

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Images hosted on PathOut server:

Images contributed by Shuanzeng Wei, M.D., Ph.D.

Nests of tumor with necrosis

Contributed by Andrey Bychkov, M.D., Ph.D.:

Follicular carcinoma with high grade progression

Case of the Week #435:

Various images

Images from AFIP:

Well defined nests (insulae) of tumor cells

Small, monotonous tumor cells

Solid pattern and abortive follicles with colloid

Solid growth pattern with prominent vessels

Peritheliomatous pattern due to necrosis

Tall appearance of epithelium

Transformation from papillary to insular carcinoma

Focal insular pattern in follicular carcinoma

Tumor has follicular, trabecular and insular patterns

Various images

Focal thyroglobulin+

Images contributed by Dr. Mark R. Wick:

Insular carcinoma

Images hosted on other servers:

Various images

Insular pattern with clefts

Small monotonous tumor cells

Fig 1 - b: insular pattern

Well defined nests and islets of small neoplastic cells

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

Images hosted on PathOut server:

Contributed by Ayana Suzuki, Cytotechnologist, Japan:

Insular pattern

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

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
Differential diagnosis
Board review 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 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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