Primary thyroid teratomas are exceedingly rare. Mature and immature variants recapitulate their gonadal counterparts (predilection for infants/children, triphasic germ layer differentiation, and favorable outcome). On the other hand, the so-called malignant teratomas affect predominantly adults and elderly, are highly aggressive, and, according to a few published cases, harbor DICER1 mutations. We describe three highly aggressive sporadic malignant teratoid thyroid tumors in 2 females (17 and 45 years) and one male (17 years). Histology showed triphasic neoplasms composed of solid nests of small primitive monomorphic cells embedded in a cellular stroma with primitive immature rhabdomyosarcoma-like (2) or pleomorphic sarcoma-like (1) phenotype. The third component was represented by TTF1+/PAX8+ primitive teratoid epithelial tubules reminiscent of primitive thyroid follicles and/or Wilms tumor, admixed with scattered respiratory- or enteric-type tubules, neuroepithelial rosettes, and fetal-type squamoid nests. Foci of cartilage were seen in two cases, but none contained mature organoid adult-type tissue or skin adnexa. SALL4 was expressed in the small cell (2) and stromal (1) component. Other germ cell markers were negative. Molecular testing revealed a known “hotspot” pathogenic DICER1 mutation in two cases. In addition, case 1 had a missense TP53 variant. This type of thyroid malignancy is distinct from genuine teratomas. The immunoprofile suggests primitive thyroid- or branchial cleft-like differentiation. Given that “blastoma” is a well-accepted terminology in the spectrum of DICER1-associated malignancies, the term “thyroblastoma” might be more convenient for these malignant teratoid tumors of the thyroid gland. Relationship of thyroblastoma to the DICER1 syndrome remains to be addressed.

原发性甲状腺畸胎瘤极为罕见。成熟和不成熟的变种概括了他们的性腺对应物（对婴儿/儿童的偏爱，三层胚芽分化和良好的结局）。另一方面，所谓的恶性畸胎瘤主要影响成年人和老年人，具有高度侵略性，并且根据一些已公开的病例，其具有DICER1突变。我们描述了2名女性（17岁和45岁）和1名男性（17岁）中的三种高度侵略性散发性恶性畸胎样甲状腺肿瘤。组织学显示三态性肿瘤由小原始单形细胞的固体巢组成，这些小单形细胞嵌入具有原始未成熟横纹肌肉瘤样（2）或多形肉瘤样（1）表型的细胞基质中。第三个成分由TTF1 + / PAX8 +代表原始甲状腺滤泡和/或Wilms肿瘤的原始类畸胎样上皮小管代表，与散布的呼吸或肠管型小管，神经上皮玫瑰花结和胎儿型鳞状巢混合。在两个病例中可见到软骨的病灶，但均未包含成熟的类器官成年型组织或皮肤附件。SALL4在小细胞（2）和基质（1）组件中表达。其他生殖细胞标记为阴性。DICER1突变2例。此外，案例1具有错义TP53变体。这种类型的甲状腺恶性肿瘤不同于真正的畸胎瘤。免疫学特征表明原始甲状腺或分支裂样分化。鉴于“母细胞瘤”是与DICER1相关的恶性肿瘤谱中公认的术语，因此“甲状腺母细胞瘤”一词可能更适合于这些甲状腺癌性畸胎瘤。甲状腺母细胞瘤与DICER1综合征的关系仍有待解决。