Squamous Cell Carcinoma, Thyroid

Nosé, Vânia

doi:10.1016/b978-0-323-52480-3.50059-7

Cited by 1 publication

(1 citation statement)

References 23 publications

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“…The metaplasia to dysplasia to neoplasia pathway has been well established in other organ systems. 20 It is controversial in the thyroid, where extensive squamous metaplasia, such as that often associated with long-standing chronic lymphocytic thyroiditis, does not appear to predispose to squamous thyroid malignancies such as the SCC subtype of ATC 21,22 ; however, squamous metaplasia has been linked to PTC in multiple meta-analyses. 23,24 A related concept, "follicular epithelial dysplasia" has been proposed in the thyroid; putative dysplastic foci show morphologic features evoking PTC that demonstrate a PTC-like immunophenotype and occur in the setting of chronic lymphocytic thyroiditis.…”

Section: Discussionmentioning

confidence: 99%

Squamous Differentiation in the Thyroid: Metaplasia, Neoplasia, or Bystander?

2021

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Background. Squamous differentiation within the thyroid is seen in a variety of settings. Squamous epithelium is non-native to the thyroid, and its debated origins span reactive metaplasia and developmental/embryologic remnants. Despite a lack of clarity as to its evolution, squamous epithelium may be associated with both neoplastic and non-neoplastic processes. Methods. Thyroid pathology reports spanning a 30-year period were reviewed for terms indicating squamous features. Associated diagnostic and clinical information was collated. Results. Four hundred and twenty seven of 17,452 (2.4%) thyroid surgical pathology cases during this period utilized terminology indicating squamous differentiation including 243 malignant (58%) and 178 benign (42%) diagnoses. There were 111 (26%) primary thyroid malignancies with squamous differentiation, 116 (28%) malignancies of non-thyroid origin including local extension from nearby cancers, and 16 (4%) malignancies of uncertain primary. Most benign lesions were non-neoplastic (84%). The minor subset representing benign neoplasia was interpreted as secondary reactive changes. Conclusion. While squamous differentiation is seen routinely in the thyroid, it is most commonly reported in malignancy. For primary thyroid malignancies reported to demonstrate a squamous component, biologically aggressive tumors were overrepresented. Available evidence suggests that multiple pathways may contribute to the presence of squamous epithelium in the thyroid including metaplasia of mature follicular cells, development from established embryonic remnants, or inception in putative, incompletely characterized stem-like cells. Our retrospective review presents an institutional landscape from which further investigation into the frequency and unique histologic and molecular context of intrathyroidal squamous differentiation as a driver or terminal event in thyroid pathophysiology.

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