Abstract：
Postchemotherapy postpubertal-type yolk sac tumors (YST) with glandular and solid phenotypes are aggressive and commonly resistant to systemic chemotherapy. These neoplasms show morphologic features that significantly overlap with those of somatic carcinomas with \"enteroblastic\" or \"fetal\" phenotype (the preferred terminology depends on the site of origin). They often present as late or very late recurrences, and their diagnosis is challenging because they frequently affect patients in an age group at risk for carcinomas of somatic origin. Recently, we incidentally identified examples of postchemotherapy glandular and solid YST with \"enteroblastic\" phenotypes and nuclear expression of beta-catenin, prompting us to further evaluate the prevalence of this phenomenon. We found nuclear expression of beta-catenin in 10 (29%) of 34 such tumors. A subset of cases with nuclear beta-catenin expression was further analyzed with a DNA sequencing panel (n = 6) and fluorescence in situ hybridization for isochromosome 12p [i(12p); n = 5]. Sequencing identified exon 3 CTNNB1 variants in 3 (50%) of 6 analyzed cases, and fluorescence in situ hybridization was positive for i(12p) in 5 of 5 cases. In conclusion, a significant subset of postchemotherapy YST with glandular or solid architecture and \"enteroblastic\" phenotype demonstrates beta-catenin alterations, suggesting that activation of Wnt signaling may play a role in the progression of these neoplasms. Moreover, nuclear beta-catenin expression in these tumors represents a potential diagnostic pitfall given that carcinomas of true somatic origin with overlapping morphology may also be positive for this marker.
摘要：
具有腺体和实体表型的青春期后型卵黄囊瘤（YST）的化疗后具有侵袭性，通常对全身化疗具有抗性。这些肿瘤的形态特征与具有“肠母细胞”或“胎儿”表型的体细胞癌的形态特征显着重叠（首选术语取决于起源部位）。它们通常表现为非常晚的复发，他们的诊断是具有挑战性的，因为他们经常影响在一个年龄组的患者在体细胞起源的癌的风险。最近,我们偶然发现了化疗后腺体和实体YST的例子，具有“肠母细胞”表型和β-连环蛋白的核表达，促使我们进一步评估这种现象的患病率。我们发现β-连环蛋白在10/34此类肿瘤中的核表达(29%)。用DNA测序组和荧光原位杂交(FISH)进一步分析了具有核β-连环蛋白表达的病例子集(n=6)的同染色体12p[i(12p);5肿瘤]。测序在3/6(50%)分析病例中鉴定外显子3CTNNB1变体,并且在5/5病例中FISH对i(12p)为阳性。总之,具有腺体/实体结构和“肠母细胞”表型的化疗后YST的重要子集显示β-catenin改变，提示Wnt信号的激活可能在这些肿瘤的进展中起作用。此外，这些肿瘤中的核β-连环蛋白表达代表了潜在的诊断陷阱，因为具有重叠形态的真正体细胞起源的癌也可能对该标志物呈阳性。
