2025 Volume 64 Issue 2 Pages 94-101
Background : Anaplastic thyroid carcinoma is a rare, but highly malignant disease. Herein, we report a case of anaplastic thyroid carcinoma that showed a variety of cytological findings on fine-needle aspiration cytology.
Case : A female patient in her 60s presented to our hospital with a rapidly enlarging neck mass. Cervical computed tomography and cervical ultrasonography revealed a mass in the right lobe of the thyroid gland and an enlarged right cervical lymph node, both of which were suspected as being malignant. Fine-needle aspiration cytology (FNAC) of the mass in the thyroid gland revealed keratinized atypical cells, which led to the suspicion of squamous cell carcinoma. Postoperative histopathological examination of the excised thyroid gland exhibited features of both papillary and anaplastic thyroid carcinomas, and the final diagnosis was anaplastic thyroid carcinoma with squamous differentiation. A review of the cytology findings revealed papillary carcinoma components, diverse multinucleated giant cells, and neutrophilic infiltration within highly atypical cell clusters.
Conclusion : When keratinizing atypical cells are found on FNAC, conditions that should be considered in the differential diagnosis include anaplastic carcinoma with squamous differentiation, squamous metaplasia of papillary carcinoma, intrathyroidal thymic carcinoma, sclerosing mucoepidermoid carcinoma with eosinophilia, and diffuse sclerosing papillary carcinoma. Anaplastic carcinoma with squamous differentiation is presumed when necrotic and inflammatory cells are seen in the background, and large atypical cells with various morphologies and mitoses are seen.
