Thyroid gland
Other carcinoma

Author: Shuanzeng Wei, M.D., Ph.D. (see Authors page)
Editor: Zubair W. Baloch, M.D., Ph.D.

Revised: 26 July 2016, last major update July 2016

Copyright: (c) 2003-2016,, Inc.

PubMed Search: Settle thyroid
Cite this page: SETTLE. website. Accessed October 25th, 2016.
Definition / General
  • Spindle Epithelial Tumor with Thymus-Like Differentiation
  • Rare initially indolent tumor of neck in young patients (4-59 years old, median age 18 years), with delayed (after 5 years) metastases to lymph nodes or lungs, indolent even with metastasis (Head Neck 2015;37:746 )
Essential Features
  • Low grade biphasic tumor with metastatic potential which occurs in young patients
  • Terminology first used in 1991 (Hum Pathol 1991;22:349)
  • Synonym: Thyroid spindle cell tumor with mucinous cysts
Radiology Images

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Cold on thyroid scan,
heterogeneous solid
and cystic on CT

Case Reports
  • Thyroidectomy, radiotherapy and chemotherapy are effective in cases with unresectable tumor or metastasis
Gross Description
  • Circumscribed or infiltrative, lobulated, white-tan cut surface.
Micro Description
  • Encapsulated or infiltrative tumor separated by sclerotic stroma
  • Biphasic pattern: spindle cells and epithelial structures (cords, tubules, papillae or glandular formation)
  • Rare monomorphic variant can have spindle cells or glandular only (Histopathology 1998;33:71)
  • No or rare lymphocytes
  • Mitotic activity or focal necrosis are rare
Micro Images

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Spindled cells with mesenchymal
appearance (AFIP)

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Spindle cells showing lobular configuration

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Periodic acid Schiff and Alcian blue stain

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Spindle cells showing
interlacing bundles

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Fig 1: Cut surface is white
and lobulated by fibrous

Cytology Description
  • Tumor with minimal epithelial component was moderately cellular with single and loosely grouped spindle cells in homogeneous metachromatic material resembling amyloid (Diagn Cytopathol 2007;35:113)
Cytology Images

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Spindle cells

Positive Stains
Differential Diagnosis