上皮样血管肉瘤（EH）是血管肉瘤的一种罕见的组织学变异，据报道在多种动物物种中都有报道，包括人类、狗、牛、马和猫。上皮样血管肉瘤由高度多形性的上皮样细胞组成，排列成索状、岛状、巢状或实性细胞区域，类似于上皮肿瘤。此外，在人类中，大约 50% 的 EH 具有细胞角蛋白 AE1/AE3 (CK AE1/AE3) 的细胞质免疫标记，这使得将它们与癌症区分开来具有挑战性。这项回顾性研究评估了 5 个兽医机构的犬 EH 病例中的 CK AE1/AE3 免疫标记。对30例病例进行CD31和CK AE1/AE3的免疫组织化学检测。 43% (13/30) 的病例检测到 CK AE1/AE3 免疫标记，肿瘤细胞的细胞质标记范围为 5% 至 100%。所有肿瘤均具有 CD31 膜免疫标记。犬 EH 中的 CK AE1/AE3 免疫标记模式与人类记录的模式非常相似，表明存在类似的诊断挑战。因此，当怀疑 EH 时，特别是在小切口皮肤和皮下活检中，建议加入血管免疫组织化学标记物，例如 CD31。

Epithelioid hemangiosarcoma (EH), a rare histological variant of hemangiosarcoma, is reported in various animal species, including humans, dogs, cows, horses, and cats. Epithelioid hemangiosarcomas are composed of highly pleomorphic epithelioid cells arranged in cords, islands, nests, or solid cellular areas, similar to epithelial neoplasms. Moreover, in humans, approximately 50% of EHs have cytoplasmic immunolabeling for cytokeratin AE1/AE3 (CK AE1/AE3), making it challenging to distinguish them from carcinomas. This retrospective study assessed the CK AE1/AE3 immunolabeling in canine EH cases from 5 veterinary institutions. Immunohistochemistry for CD31 and CK AE1/AE3 was performed on 30 cases. CK AE1/AE3 immunolabeling was detected in 43% (13/30) of cases, with cytoplasmic labeling ranging from 5% to 100% of neoplastic cells. All tumors consistently had membranous immunolabeling for CD31. The CK AE1/AE3 immunolabeling pattern in canine EHs closely resembled those documented in humans, indicating a similar diagnostic challenge. Therefore, it is recommended to include a vascular immunohistochemistry marker, such as CD31, whenever EH is suspected, particularly in small incisional cutaneous and subcutaneous biopsies.