Endometrial somatically derived yolk sac tumors are characterized by yolk sac morphology with AFP, SALL-4, and/or Glypican-3 immunoexpression. Yolk sac marker expression, however, is not limited to tumors with overt yolk sac histology. Three hundred consecutive endometrial malignancies were assessed for immunomarkers of yolk sac differentiation. Of these, 9% expressed ≥1 yolk sac marker, including 29% of high-grade tumors. Only 3 (1%) met morphologic criteria for yolk sac differentiation; these were originally diagnosed as serous, high-grade NOS, and dedifferentiated carcinoma. Two were MMR-intact and comprised exclusively of yolk sac elements, while the dedifferentiated case was MMR deficient and had a background low-grade endometrioid carcinoma; this case also showed BRG1 loss. All 3 were INI1 intact. Nonspecific yolk sac marker expression was seen in 14 carcinosarcomas, 4 endometrioid, 2 serous, 1 clear cell, 1 dedifferentiated, 1 mixed serous/clear cell, and 1 mesonephric-like carcinoma. INI1 was intact in all cases; one showed BRG1 loss. Twenty were MMR-intact, and 4 were MMR deficient. All MMR-deficient cases with yolk sac marker expression, both with and without true yolk sac morphology, had no evidence of residual disease on follow-up, whereas 82% of MMR-intact cases developed recurrent/metastatic disease. In summary, endometrial somatically derived yolk sac tumors were rare but under-recognized. While AFP immunostaining was specific for this diagnosis, Glypican-3 and SALL-4 expression was seen in a variety of other high-grade carcinomas. INI1 loss was not associated with yolk sac morphology or immunomarker expression in the endometrium, and BRG1 loss was rare. All patients with MMR-deficient carcinomas with yolk sac immunoexpression +/- morphology were disease-free on follow-up, whereas the majority of MMR-intact cancers showed aggressive disease.

中文翻译：

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子宫内膜癌中的卵黄囊分化：体细胞来源的卵黄囊肿瘤与具有卵黄囊标志物非特异性免疫表达的癌症的发病率和临床病理特征。

子宫内膜体细胞来源的卵黄囊肿瘤的特征是具有 AFP、SALL-4 和/或 Glypican-3 免疫表达的卵黄囊形态。然而，卵黄囊标志物表达并不限于具有明显卵黄囊组织学的肿瘤。对三百个连续的子宫内膜恶性肿瘤进行了卵黄囊分化免疫标记物的评估。其中，9% 表达≥1 个卵黄囊标志物，其中包括 29% 的高级别肿瘤。只有 3 个（1%）符合卵黄囊分化的形态学标准；这些最初被诊断为浆液性、高级别 NOS 和去分化癌。其中两个是 MMR 完整的，仅由卵黄囊成分组成，而去分化病例是 MMR 缺陷的，并且有低级别子宫内膜样癌背景；该病例也显示 BRG1 丢失。所有 3 个 INI1 均完好无损。在 14 例癌肉瘤、4 例子宫内膜样癌、2 例浆液性癌、1 例透明细胞癌、1 例去分化癌、1 例混合浆液性/透明细胞癌和 1 例中肾样癌中观察到非特异性卵黄囊标志物表达。 INI1 在所有情况下均完好无损；一个显示 BRG1 丢失。 20 名 MMR 完整，4 名 MMR 缺陷。所有具有卵黄囊标志物表达的 MMR 缺陷病例，无论有或没有真正的卵黄囊形态，在随访中都没有残留疾病的证据，而 82% 的 MMR 完整病例出现复发/转移性疾病。总之，子宫内膜体细胞来源的卵黄囊肿瘤很少见，但尚未得到充分认识。虽然 AFP 免疫染色对该诊断具有特异性，但 Glypican-3 和 SALL-4 表达在多种其他高级癌症中也可见到。 INI1 缺失与子宫内膜中卵黄囊形态或免疫标记物表达无关，并且 BRG1 缺失很少见。所有具有卵黄囊免疫表达+/-形态学的MMR缺陷型癌症患者在随访中均无疾病，而大多数MMR完整的癌症则表现出侵袭性疾病。