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Anaplastic Thyroid Carcinoma, Squamous Cell Carcinoma Pattern

      An older man presented with a thyroid mass. The tumor was resected and showed a primary squamous cell carcinoma of the thyroid, which is now classified as anaplastic thyroid carcinoma, squamous cell carcinoma pattern.
      What is the most accurate statement regarding this tumor?
      • a.
        Anaplastic thyroid carcinomas are the most common type of thyroid carcinoma
      • b.
        Anaplastic thyroid carcinomas are never diagnosed concurrently with or subsequent to well-differentiated thyroid carcinoma
      • c.
        Anaplastic thyroid carcinomas are a subtype of medullary thyroid carcinoma
      • d.
        Anaplastic thyroid carcinoma is a rare and almost uniformly fatal follicular cell–derived thyroid carcinoma
      Answer: d. Anaplastic thyroid carcinoma is a rare, almost uniformly fatal follicular cell–derived thyroid carcinoma.
      Anaplastic thyroid carcinoma can have a variety of histologic patterns. Squamous cell carcinoma of the thyroid was previously listed separately in the World Health Organization tumor classification; however, it is now regarded as a subtype of anaplastic thyroid carcinoma and classified by the World Health Organization as anaplastic thyroid carcinoma, squamous cell carcinoma pattern (Figures 1 and 2).
      • Baloch Z.W.
      • Asa S.L.
      • Barletta J.A.
      • et al.
      Overview of the 2022 WHO classification of thyroid neoplasms.
      Similar to other histologic types of anaplastic thyroid carcinoma, squamous cell carcinoma phenotype confers a poor prognosis.
      • Lam A.K.
      Squamous cell carcinoma of thyroid: a unique type of cancer in World Health Organization classification.
      ,
      • Xu B.
      • Fuchs T.
      • Dogan S.
      • et al.
      Dissecting anaplastic thyroid carcinoma: a comprehensive clinical, histologic, immunophenotypic, and molecular study of 360 cases.
      Anaplastic thyroid carcinoma often has BRAF p.V600E mutation with a history of or concurrent papillary thyroid carcinoma or other differentiated thyroid carcinomas.
      • Xu B.
      • Fuchs T.
      • Dogan S.
      • et al.
      Dissecting anaplastic thyroid carcinoma: a comprehensive clinical, histologic, immunophenotypic, and molecular study of 360 cases.
      ,
      • Chen T.Y.
      • Lorch J.H.
      • Wong K.S.
      • Barletta J.A.
      Histological features of BRAF V600E-mutant anaplastic thyroid carcinoma.
      RAS and BRAF p.V600E are considered early driver mutations and TP53 and TERT promoter mutations are late events in the pathogenesis of anaplastic thyroid carcinoma.
      • Volante M.
      • Lam A.K.
      • Papotti M.
      • Tallini G.
      Molecular pathology of poorly differentiated and anaplastic thyroid cancer: what do pathologists need to know?.
      Figure thumbnail gr1
      Figure 1Anaplastic thyroid carcinoma, squamous cell carcinoma pattern.
      Figure thumbnail gr2
      Figure 2Anaplastic thyroid carcinoma, squamous cell carcinoma pattern.

      References

        • Baloch Z.W.
        • Asa S.L.
        • Barletta J.A.
        • et al.
        Overview of the 2022 WHO classification of thyroid neoplasms.
        Endocr Pathol. 2022; 33: 27-63
        • Lam A.K.
        Squamous cell carcinoma of thyroid: a unique type of cancer in World Health Organization classification.
        Endocr Relat Cancer. 2020; 27: R177-R192
        • Xu B.
        • Fuchs T.
        • Dogan S.
        • et al.
        Dissecting anaplastic thyroid carcinoma: a comprehensive clinical, histologic, immunophenotypic, and molecular study of 360 cases.
        Thyroid. 2020; 30: 1505-1517
        • Chen T.Y.
        • Lorch J.H.
        • Wong K.S.
        • Barletta J.A.
        Histological features of BRAF V600E-mutant anaplastic thyroid carcinoma.
        Histopathology. 2020; 77: 314-320
        • Volante M.
        • Lam A.K.
        • Papotti M.
        • Tallini G.
        Molecular pathology of poorly differentiated and anaplastic thyroid cancer: what do pathologists need to know?.
        Endocr Pathol. 2021; 32: 63-76