Poorly differentiated thyroid carcinoma (PDTC) is a rare malignancy, representing ~1% of all thyroid tumors. It is characterized by high-grade histologic features without the anaplastic characteristics observed in anaplastic thyroid carcinoma. Although rare in children and young adults, there is emerging evidence of clinical and genetic differences with PDTC in adults. We present a case of a 19-year-old female with a right thyroid lobe nodule classified as an EU-TIRADS 5 lesion. Subsequent FNAC showed a cellular aspirate of solitary cells and scant microfollicles with variable nuclear irregularities, which was designated a Bethesda class IV lesion. Thyroidectomy revealed histopathological features consistent with PDTC, including solid/trabecular growth, increased mitotic activity, central necrosis, and extensive vascular invasion. Molecular analysis identified germline and somatic DICER1 mutations in the absence of other established driver mutations of PDTC. This case report describes the fourth reported patient with a PDTC and germline DICER1 mutation. Our findings contribute to a limited body of literature on pediatric/young adult PDTC cases and highlight the pivotal role of DICER1 mutations. Emerging evidence suggests that pediatric PDTC may exhibit unique clinical and genetic characteristics, prompting further research into its molecular profile.

中文翻译：

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DICER1 突变定义了儿童和年轻人低分化甲状腺癌的概况：病例报告和文献综述。


低分化甲状腺癌 (PDTC) 是一种罕见的恶性肿瘤，约占所有甲状腺肿瘤的 1%。其特点是具有高级组织学特征，但没有在甲状腺未分化癌中观察到的未分化特征。尽管在儿童和年轻人中很少见，但有新的证据表明成人 PDTC 存在临床和遗传差异。我们介绍了一名 19 岁女性的病例，她的右甲状腺叶结节被归类为 EU-TIRADS 5 病变。随后的 FNAC 显​​示细胞吸出的孤立细胞和少量微滤泡，核不规则性各异，被指定为 Bethesda IV 级病变。甲状腺切除术显示与 PDTC 一致的组织病理学特征，包括实性/小梁生长、有丝分裂活性增加、中央坏死和广泛的血管侵犯。在没有其他已确定的 PDTC 驱动突变的情况下，分子分析鉴定了种系和体细胞 DICER1 突变。本病例报告描述了第四例报告的患有 PDTC 和种系 DICER1 突变的患者。我们的研究结果为有关儿科/青少年 PDTC 病例的有限文献做出了贡献，并强调了 DICER1 突变的关键作用。新的证据表明，儿科 PDTC 可能表现出独特的临床和遗传特征，促使对其分子谱进行进一步研究。