Abstract：
Perivascular epithelioid cell tumors (PEComas), rare mesenchymal tumors with myomelanocytic differentiation, can be a diagnostic challenge, often requiring a panel of immunohistochemical markers. Preferentially expressed antigen in melanoma (PRAME) is a relatively new antigen with utility in diagnosing melanomas. This study aimed to survey PRAME expression patterns in the PEComa family of tumors and morphologic mimics. Twenty cases of PEComas and 27 non-PEComas (10 leiomyosarcomas, 3 smooth muscle tumors of uncertain malignant potential [STUMPs], 11 leiomyomas, 1 uterine inflammatory myofibroblastic tumor [IMT], and 2 low-grade endometrial stromal sarcomas [LGESSs]) were stained with PRAME and compared to previously performed HMB45 and Melan-A stains, when available. Tumors showing no or barely perceptible PRAME staining at 10× were considered negative. Tumors were considered positive if there was full nuclear staining evident at 10× in at least one 10× field. Diffuse staining was defined as positivity in at least 80% of tumor nuclei. Overall, PRAME was expressed in 70% of PEComas, with diffuse positivity in 60%. However, PRAME was not specific for PEComas, with immunopositivity in the majority (70%) of uterine leiomyosarcoma cases, though negative in STUMP, leiomyoma, IMT, and LGESS cases. PRAME sensitivity was 70% and specificity was 74%, while HMB45 was more sensitive (90%) and specific (100%), but only 15% of PEComas showed diffuse staining. Melan-A staining was less common than HMB45 or PRAME, with only 18.8% sensitivity but 100% specificity. Among gynecologic PEComas, PRAME was expressed in 75% overall and enriched among malignant cases (85.7% positive). As part of an immunohistochemical panel, PRAME could be useful in the workup of PEComa cases. In the future, PRAME-specific immunotherapies may be beneficial in treating patients with malignant PEComas.
摘要：
血管周围上皮样细胞肿瘤（PEComa），罕见的间充质肿瘤与平滑肌细胞分化，可能是一个诊断挑战，通常需要一组免疫组织化学（IHC）标记。在黑素瘤中优先表达的抗原(PRAME)是在诊断黑素瘤中具有效用的相对新的抗原。这项研究旨在调查PEComa家族肿瘤和形态模拟物中的PRAME表达模式。20例PEComas和27例非PEComas（10平滑肌肉瘤，3恶性潜能不确定的平滑肌肿瘤（STUMP），11平滑肌瘤,用PRAME对1例子宫炎性肌纤维母细胞瘤（IMT）和2例低级别子宫内膜间质肉瘤（LGESS）进行染色，并与以前进行的HMB45和Melan-A染色进行比较，可用时。在10x处没有或几乎感觉不到PRAME染色的肿瘤被认为是阴性的。如果在至少一个10x视野中在10x处明显存在完全核染色,则认为肿瘤是阳性的。弥漫染色定义为在至少80%的肿瘤核中阳性。总的来说,PRAME在70％的PEComas中表达，弥漫性阳性为60％。然而,PRAME不是针对PEComas的，在大多数（70％）子宫平滑肌肉瘤病例中具有免疫阳性，虽然在STUMP中呈阴性，平滑肌瘤,IMT和LGESS案例。PRAME敏感性为70%，特异性为74%，而HMB45更敏感(90%)和特异性(100%)，但只有15%的PEComas表现出弥漫性染色。Melan-A染色不如HMB45或PRAME常见，灵敏度仅为18.8%，特异性为100%。在妇科PEComas中，PRAME在75％的总体中表达，在恶性病例中丰富（85.7％阳性）。作为免疫组织化学小组的一部分，PRAME在PEComa病例的检查中可能很有用。在未来,PRAME特异性免疫疗法可能有益于治疗恶性PEComas患者。
