A Diffusely Hardened Thyroid Gland and Multiple Neck Lymphadenopathies

Aman inhis60spresentedwithneck swelling.Onphysical examinationadiffusely hardened thyroidglandandmultiple neck lymphadenopathieswere found.Contrast-enhancedchest andneckcomputed tomographic (CT) imaging revealed multiple cervical lymph nodes anddiffuse thyroid heterogeneitywith a low-density nodule in the right lobe.No thoracic lesionswereobserved.Rigid laryngoscopy, thorough head and neck examination, as well as whole-body positron emission tomographic imaging excluded tumors from the upper aerodigestive tract or distantmetastasis. A fine-needle aspiration cytologic specimen of the cervical lymph node revealed necrosis and atypical squamous cells. Total thyroidectomy combined with bilateral neck lymph node dissectionwas performed. The surgical specimen revealed an ill-defined, nonencapsulated tumor (52 × 32 × 25mm) involvingthewhole thyroidgland(Figure,A).Histopathologic findings showed a neoplastic cell proliferation, formingsheets,nests, andcompactmasses that invaded thestromal thyroid tissue. The tumor cells revealed scant eosinophilic cytoplasm with individual keratinization. Periodic acid–Schiff (PAS) andAlcian blue stains were negative for mucin deposits. The surrounding stroma showed squamousmetaplasia and lymphocytic infiltration exhibiting large follicles with prominent germinal centers (Figure, B). Extrathyroid infiltration, comedo necrosis, and extensive lymphovascular invasionwereobserved.Therewerenohistologic findings suggestive of preexisting papillary, medullary, or anaplastic or undifferentiatedcarcinoma.The immunohistochemicalprofileof the tumor cells revealed strongpositivity for p63 (Figure, C) andCK5/6, 34betaE12, CK (AE1/AE3), and CK19 antibodies. Results for PAX-8 weremoderatelypositive (Figure,D).Results forCD5,calcitonin, thyroglobulin, TTF-1, CD56, and CEA antibodies were all negative. Regional metastases were detected in 58 of 67 lymph nodes examined on the right side and 43 of 67 on the left side. What is your diagnosis? A B