Poorly differentiated thyroid carcinoma (PDTC) refers to a malignant tumour that displays an intermediate prognosis between well-differentiated carcinomas and anaplastic thyroid carcinomas (ATC). In the thyroid, pleomorphic giant cells are observed in ATC or in some non-neoplastic thyroid diseases. We described the case of a 43-year-old woman with a 34-mm nodule in her thyroid right lobe. Microscopic examination revealed an encapsulated tumour with a main solid growth pattern and extensive capsular invasion. Multiple images of angioinvasion were observed. There was neither necrosis nor inflammation. Most of the tumour cells were medium-sized and intermingled with pleomorphic giant tumour cells with bizarre features. The immunoprofile (keratins +, TTF1+, Pax 8+) proved their thyroid origin. By NGS, no molecular alteration was identified. The patient was treated by surgery and radioiodine therapy and she has no recurrence after a follow-up of 24 months. Our case meets all the histological criteria of the Turin proposal for PDTC but with pleomorphic giant cells and is very different from ATC according to clinical, histological and immunohistochemical features. Pleomorphic tumour giant cells in thyroid carcinomas could be present in PDTC and do not always represent dedifferentiation and more aggressive carcinoma, thyroid neoplasm.

中文翻译：

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低分化甲状腺癌，多形性巨细胞一例报道。

低分化甲状腺癌（PDTC）是指在高分化癌和间变性甲状腺癌（ATC）之间显示中等预后的恶性肿瘤。在甲状腺中，在ATC或某些非肿瘤性甲状腺疾病中观察到多形巨细胞。我们描述了一个43岁的女性，其甲状腺右叶中有一个34毫米结节的病例。显微镜检查发现包囊的肿瘤具有主要的实体生长模式和广泛的包膜浸润。观察到血管浸润的多个图像。既没有坏死也没有炎症。多数肿瘤细胞为中等大小，并与具有奇异特征的多形巨瘤细胞混合。免疫特征（角蛋白+，TTF1 +，Pax 8+）证明了它们的甲状腺来源。通过NGS，未发现分子改变。该患者接受了手术和放射碘疗法的治疗，随访24个月后未复发。我们的病例符合都灵关于PDTC的建议的所有组织学标准，但具有多形巨细胞，并且根据临床，组织学和免疫组化特征与ATC截然不同。甲状腺癌中的多形性肿瘤巨细胞可能存在于PDTC中，并不总是代表去分化和更具侵袭性的甲状腺癌。