Anaplastic thyroid carcinoma with osteoclast-like giant cells: a case report and a study of a potential therapeutic approach.

Anaplastic thyroid carcinoma (ATC) is a highly aggressive neoplasm with no effective treatment options. ATC with osteoclast-like giant cells (OGCs; ATC/OGC) is a rare variant of ATC, and no detailed pathological examination has been reported to date. A 59-year-old woman presented with sudden neck swelling. Computed tomography revealed a 5 cm tumor in the thyroid gland, which was surgically resected. Pathological examination revealed a diagnosis of ATC/OGC. The patient succumbed to progressive lung metastases within four months despite postoperative lenvatinib therapy. Immunohistochemical (IHC) examination indicated absence of PD-L1 expression in the OGCs, which comprised the majority of the tumor, with only sparse T cell infiltration in the area occupied by OGCs. Increased TGF-β expression was observed in the area containing OGCs, and both OGCs and infiltrating myeloid cells, including CD1a/CD11c-positive dendritic cells and CD68/CD163/CD204-positive macrophages, appeared to produce TGF-β. Pathological analysis of this case suggests that OGCs might be involved in immune suppression by secreting TGF-β, potentially serving as a critical cytokine in the immunosuppressive microenvironment of ATC/OGC. TGF-β-targeted therapy might be useful in the treatment of this very rare subtype of ATC.