Laboratoire Central D'Anatomie Pathologique, Hôpital L. Pasteur, University of Nice, Nail's Dermatology Consultations, Nice, Cannes, France.
Am J Dermatopathol. 2022 Jul 1;44(7):499-502. doi: 10.1097/DAD.0000000000002156. Epub 2022 Feb 25.
Recent studies have argued that melanocyte preferentially expressed nuclear antigen in melanoma (PRAME) is a sensitive and specific immunohistochemical marker of melanoma, including acral melanoma. In addition, loss of p16 expression has recently been suggested to have diagnostic utility in acral melanocytic tumors. The purpose of this study was to report PRAME expression in 3 cases of melanocytic activation (MAN). There were 2 men and 1 woman ranging in age at diagnosis from 46 years to 78 years (mean 61, 6 years). All cases involved a single digit. One lesion was in the fingernail (fifth finger), whereas the remaining 2 lesions were in the toenails (hallux). All the patient presented with a longitudinal melanonychia. The width of the lesions varied from 3 mm (2 cases) to 4 mm (1 case). The duration of the lesions before diagnosis varied from 12 to 24 months. Distinction of MAN from melanoma in situ is not always easy. Some morphological misleading features are illustrated in this study: (1) the suprabasal location of matrix melanocytes with long and thick dendrites within the 2-4 germinative cell layers; (2) the microconfluence of 2 melanocytes and rare melanocytes with a relatively large nucleus, however in a general context of melanocyte scarcity; and (3) the occasional nonspecific nuclear microphtalmia-associated transcription factor (MITF) staining of keratogeneous cells. Such staining could suggest a pagetoid spread of melanocytes in the keratogenous zone. PRAME antibody revealed a strong and diffuse staining in all cases. In addition, all cases were p16 negative. In this study, the melanocyte count inferior to 9 melanocytes/mm and the lack of nuclear atypia or confluence of melanocytes permitted a confident diagnosis of MAN. Limitations of our study lie largely in the small number of cases. Despite this, the expression of PRAME in some MAN seems to hamper its diagnostic value in differentiating benign from malignant lesion.
最近的研究表明，黑色素瘤中优先表达的核抗原（PRAME）是黑色素瘤的一种敏感和特异的免疫组化标志物，包括肢端黑色素瘤。此外，最近有研究表明，p16 表达缺失在肢端黑色素细胞肿瘤中有诊断价值。本研究旨在报告 3 例黑素细胞激活（MAN）病例中 PRAME 的表达。患者为 2 男 1 女，发病年龄为 46 岁至 78 岁（平均 61.6 岁，6 年）。所有病例均累及单个指（趾）。1 例病变位于指甲（第五指），其余 2 例病变位于趾甲（大脚趾）。所有患者均表现为纵向黑甲。病变的宽度从 3mm（2 例）至 4mm（1 例）不等。诊断前病变的持续时间从 12 个月到 24 个月不等。MAN 与原位黑色素瘤的鉴别并不总是容易的。本研究中存在一些形态学上的误导特征：（1）在 2-4 个生发细胞层内基质黑素细胞的基底层位置，具有长而厚的树突；（2）2 个黑素细胞微融合，以及罕见的细胞核相对较大的黑素细胞，但在黑素细胞稀少的一般背景下；（3）角质形成细胞偶尔出现非特异性核小眼相关转录因子（MITF）染色。这种染色可能提示黑色素细胞在角质形成区呈节段性扩散。所有病例均表现为 PRAME 抗体强而弥漫性染色，此外，所有病例均为 p16 阴性。在本研究中，黑素细胞计数低于 9 个/ mm，且无核异型性或黑素细胞融合，可作出明确的 MAN 诊断。本研究的局限性主要在于病例数量较少。尽管如此，PRAME 在某些 MAN 中的表达似乎使其在区分良性和恶性病变方面的诊断价值受到阻碍。
