Department of Pathology, University of Virginia, Charlottesville, VA, USA.
Departments of Dermatology and Pathology, University of Arkansas, Little Rock, AR, USA.
Histopathology. 2021 Jun;78(7):1000-1008. doi: 10.1111/his.14312. Epub 2021 Apr 2.
Lentigo maligna (LM), the most common type of melanoma in situ, is a diagnostically challenging lesion for pathologists due to abundant background melanocytic hyperplasia in sun-damaged skin. Currently, no laboratory methods reliably distinguish benign from malignant melanocytes. However, preferentially expressed antigen in melanoma (PRAME) has shown promise in this regard, and could potentially be applied to diagnosis and margin assessment in difficult cases of LM.
Ninety-six cases with a diagnosis of LM (n = 77) or no residual LM (n = 19) following initial biopsy were identified and stained with an antibody directed towards PRAME. Immunohistochemistry (IHC) was scored as positive or negative, and measurement of histological margins by PRAME was performed and compared to the measurement of histological margins using conventional methods [haematoxylin and eosin (H&E) and/or sex-determining region Y-box 10 (SOX10) and/or Melan-A]. Of cases with LM, 93.5% (72 of 77) were PRAME and 94.7% (18 of 19) of cases with no residual LM were PRAME . Of the 35 cases with no margin involvement by PRAME or conventional assessment, 14 cases (40.0%) had no difference in measurement, 17 (48.6%) had a difference of 1 mm or less and four (11.4%) differed by between 1 and 3.5 mm. There was a high correlation between margin assessment methods (r = 0.97, P < 0.0001).
PRAME IHC is a sensitive (93.5%) and specific (94.7%) method for diagnosing LM on biopsy and excision, and measurement of histological margins by PRAME shows a high correlation with conventional methods for margin assessment. Furthermore, the nuclear expression of PRAME makes it a good target for use in dual-colour IHC stains.
恶性雀斑样痣（LM）是原位黑色素瘤中最常见的类型，由于日光损伤皮肤中存在大量黑素细胞增生，对病理学家来说是一种具有挑战性的诊断病变。目前，尚无实验室方法能够可靠地区分良性和恶性黑素细胞。然而，黑色素瘤优先表达抗原（PRAME）在这方面显示出了希望，并且可能应用于 LM 等困难病例的诊断和边缘评估。
鉴定了 96 例最初活检诊断为 LM（n=77）或无残留 LM（n=19）的病例，并使用针对 PRAME 的抗体进行染色。免疫组织化学（IHC）评分阳性或阴性，并对 PRAME 进行组织学边缘测量，并与使用常规方法（苏木精和伊红（H&E）和/或性别决定区 Y 盒 10（SOX10）和/或 Melan-A）进行的组织学边缘测量进行比较。在 LM 病例中，93.5%（72/77）为 PRAME阳性，94.7%（18/19）无残留 LM 为 PRAME 阳性。在 35 例 PRAME 或常规评估无边缘受累的病例中，14 例（40.0%）测量无差异，17 例（48.6%）差异在 1mm 或以下，4 例（11.4%）差异在 1 至 3.5mm 之间。边缘评估方法之间具有高度相关性（r=0.97，P<0.0001）。
PRAME IHC 是一种在活检和切除时诊断 LM 的敏感（93.5%）和特异（94.7%）方法，PRAME 对组织学边缘的测量与常规边缘评估方法具有高度相关性。此外，PRAME 的核表达使其成为双染免疫组化染色的良好靶标。
