Thymic carcinoma

Thymic squamous cell carcinoma

Last author update: 1 December 2012
Last staff update: 16 January 2023 (update in progress)

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PubMed Search: Thymic carcinoma general

Hanni Gulwani, M.B.B.S.
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Cite this page: Gulwani H. Thymic squamous cell carcinoma. website. Accessed June 4th, 2023.
Definition / general
  • By definition, has overt cellular anaplasia
  • Ages ≥ 50 years; occasionally children
Diagrams / tables

Images hosted on other servers:

Proposed stage T1, tumor limited to thymic gland

Proposed stage T2, tumor invades nearby structures

Proposed stage T3, direct (continuous) extrathoracic tumor extension beyond thoracic inlet or below diaphragm

Clinical features
  • Associated with hypercalcemia, elevated parathyroid hormone levels, pulmonary sarcoidosis
  • Not associated with paraneoplastic syndromes such as myasthenia gravis or pure red cell aplasia
  • Patients usually present with mass related symptoms
  • Aggressive clinical course
  • Must exclude other primaries, which are much more common (lung, trachea, bronchi, esophagus)
  • Usually squamous cell carcinoma and variants (lymphoepithelioma-like, basaloid)
  • Proposed staging system (Am J Clin Pathol 2012;138:115)
Radiology images

Contributed by Lina Hu, M.D. (Case #479)

Mass with irregular, infiltrative borders

Prognostic factors
  • May be less aggressive than commonly believed; important prognostic factors are lymph node status and tumor size (Am J Clin Pathol 2012;138:103)
  • Keratinizing: good prognosis with few fatalities if well differentiated
Case reports
Gross description
  • Unencapsulated, no internal fibrous septation, firm / hard / gritty with gray-white cut surface, necrosis and hemorrhage
Microscopic (histologic) description
  • Usually cohesive cellular growth, regularly round / oval nuclear outlines, eosinophilic nucleoli, geographic necrosis
  • Usually foci of medullary differentiation, abortive Hassall corpuscles, rosettes, gland-like spaces, T lymphocytes; no perivascular spaces
  • Keratinizing:
    • Similar to tumor in skin, lung, other sites
    • Lobular growth with fibrous bands
    • Nests and cords of large polyhedral cells with intercellular bridges
    • Vesicular or hyperchromatic nuclei, prominent nucleoli, eosinophilic or glassy cytoplasm, keratin pearls
    • Also angiolymphatic invasion, necrosis
    • Rarely coexists with thymoma
  • Non-keratinizing
    • Angular nests of malignant squamous cells in desmoplastic stroma
    • No intercellular bridges, no eosinophilic cytoplasm, no keratin pearls
Microscopic (histologic) images

Contributed by Lina Hu, M.D. (Case #479)


KIT / CD117


Positive stains
Negative stains
Electron microscopy description
  • Well formed desmosome-like intercellular junctions, cytoplasmic tonofilaments that may insert into junctional complexes
Differential diagnosis
Board review style question #1
Which 2 antibodies are most helpful in diagnosing thymic carcinoma?

A. CK5/6, 34bE12
B. CD5, p63
C. CEA, synaptophysin
D. p63, p40
E. KIT / CD117, INSM1
Board review style answer #1
B. CD5 combined with p63 are helpful thymic markers.

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Reference: Thymic squamous cell carcinoma
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