FIG. 2.
Representative histopathology of pre- and post-BRAF/MEK-treated anaplastic thyroid carcinomas. Residual tumor viability and representative histopathology. (A, B) Show representative histologic slides from Patient 2. (C–E) Show representative slides from Patient 5. (A) Pretreatment biopsy showing pleomorphic cells with eosinophilic cytoplasm with squamoid features growing in cords. The background is desmoplastic with scattered inflammatory infiltrate (hematoxylin and eosin stain, 400 × magnification). (B) Post-treatment surgical resection at low power magnification (hematoxylin and eosin stain, 40 × magnification) shows large fibrotic areas of the treated tumor bed with scattered viable tumor nests (left side); the inset shows a viable tumor area with desmoplastic stroma (100 × magnification). (C) Diagnostic core biopsy shows irregular squamoid tumor cells in a fibrotic stroma (hematoxylin and eosin stain, 100 × magnification). (D) Post-treatment, the surgical resection shows large areas of fibrosis with scattered follicles of residual well-differentiated papillary thyroid carcinoma that retain BRAFV600E expression by immunohistochemistry (inset) (100 × magnification); (E) Post-treatment area that showed progression in the scalp shows viable anaplastic thyroid carcinoma growing in squamoid nests similar to the pretreatment biopsy (hematoxylin and eosin stain, 100 × magnification). This tumor also retains BRAFV600E immmunoexpression (immunoslide not shown).