Thyroid gland
Other carcinoma
Poorly differentiated thyroid carcinoma

Author: Shahidul Islam, M.D., Ph.D. (see Authors page)

Revised: 8 September 2017, last major update March 2009

Copyright: (c) 2003-2017,, Inc.

PubMed Search: Poorly differentiated thyroid carcinoma

Related Topic: Poorly differentiated carcinoma with rhabdoid features
Cite this page: Poorly differentiated thyroid carcinoma. website. Accessed December 14th, 2017.
Definition / general
  • Diffuse insular (island-like) growth pattern; some authors include solid or trabecular growth patterns
  • May be a poorly differentiated form of papillary or follicular carcinoma, but distinct from widely invasive follicular carcinoma (Am J Surg Pathol 1997;21:1466)
  • May be closely related to tumor described by Langhans in 1907 as "wuchernde Struma" (Am J Surg Pathol 1984;8:655)
  • Old term - insular carcinoma
  • Older patients, more common in Europe and South America than U.S.
Clinical features
Prognostic factors
  • Tumors with > 50% poorly differentiated component have poorer prognosis than < 50% (Cancer 2007;110:1209)
Case reports
Gross description
  • Large, gray-white, extensive necrosis, invasive
Gross images

Images hosted on PathOut server:

AFIP image

Massive cervical lymph node metastasis (AFIP)

Contributed by Dr. Mark R. Wick

Images hosted on other servers:

(A) Well demarcated tumor with prominent vascularity

Tumor has replaced most
of thyroid gland and has
invasive growth pattern,
multiple foci of necrosis exist

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:
    • Pleomorphic tumor cells without any organoid (follicle-related) arrangement
    • May have small globoid cells with uniform nuclei and intracytoplasmic thyroglobulin deposits resembling primordial fetal thyroid cells
    • May have peritheliomatous pattern (tumor cells around blood vessels with necrosis of tumor cells further away from vessels), vascular and capsular invasion; better differentiated tumor may also be present
    • Often artifactual clefts between nests of cells
Microscopic (histologic) images

Scroll to see all images.

Images hosted on PathOut server:

COW #435

Insular carcinoma, contributed by Dr. Mark R. Wick

Focal thyroglobulin+

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

Follicular carcinoma with high grade progression

Images from AFIP:

Well defined nests (insulae) of tumor cells

Insulae composed of 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 carcinoma to insular carcinoma

Focal insular pattern in follicular carcinoma

Tumor has follicular, trabecular and insular patterns

Various images

Images hosted on other servers:

Various images

Insular pattern with clefts

Small monotonous tumor cells

(B) Insular pattern

Well defined nests and islets of small neoplastic cells

Cytology description
  • Highly cellular with cell clusters or trabeculae that may merge with follicular areas, often associated with microfollicles
  • Necrotic background, scant colloid
  • Cells have poorly defined cytoplasm and cytoplasmic vacuoles, mild atypia with hyperchromatic nuclei (Cancer 1999;87:196, Am J Clin Pathol 1990;94:687)
Cytology images

Images hosted on other servers:

Nesting pattern of cells

Cellular smear has overlapping cells with round, regular nuclei

Large clusters and single cells

Cellular nests of loosely cohesive cells

Overlapping cells with mild atypia

Small microfollicle of tumor cells

Cells have finely
cytoplasm and
round / oval nuclei

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

A. Solid, trabecular or insular growth
B. Vascular invasion, high grade nuclei and increased mitotic activity
C. Absence of conventional nuclear features of papillary thyroid carcinoma
D. Necrosis

Board review answer #1
B. Vascular invasion, high grade nuclei and increased mitotic activity.

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 and/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.