Department of Pathology and Laboratory Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA.
Biomedical Data Science Department, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
J Cutan Pathol. 2021 Apr;48(4):519-525. doi: 10.1111/cup.13916. Epub 2020 Nov 25.
Traditionally, most cutaneous nevi show a gradient of HMB45 (human melanoma black 45) and negative PRAME (preferentially expressed antigen in melanoma) immunostaining, while melanomas often show irregularly positive, diffusely positive or completely negative HMB45 expression, and PRAME immunopositivity. However, we have occasionally observed benign halo nevi with loss of HMB45 gradient, raising diagnostic consideration for melanoma. The purpose of this study was to elucidate the expression pattern of HMB45 and PRAME in nevi with the halo phenomenon (NHP).
PRAME and HMB45 staining patterns in 20 cases of NHP and 16 cases of conventional nevi were evaluated using light microscopy. An HMB45 gradient was defined as immunopositivity in only superficial melanocytes. HMB45 aberrant expression consisted of superficial and deep immunopositivity.
Aberrant HMB45 expression was observed in 10 of 20 NHP (50%). A gradient of HMB45 staining was seen in most conventional nevi, with only one showing focal weak expression in the deep dermis (6.3%). All cases of NHP and conventional nevi showed essentially negative immunostaining by PRAME.
Aberrant HMB45 expression in NHP is not uncommon and may be a diagnostic pitfall. Negative PRAME immunostaining may be a reassuring finding to help differentiate halo nevus from malignant melanoma.
传统上，大多数皮肤痣显示 HMB45（人类黑色素瘤黑 45）和 PRAME（黑色素瘤中优先表达的抗原）免疫染色的梯度，而黑色素瘤通常表现为不规则阳性、弥漫阳性或完全阴性的 HMB45 表达和 PRAME 免疫阳性。然而，我们偶尔会观察到良性晕痣失去 HMB45 梯度，这引起了对黑色素瘤的诊断考虑。本研究的目的是阐明具有晕环现象（NHP）的痣中 HMB45 和 PRAME 的表达模式。
使用光学显微镜评估 20 例 NHP 和 16 例常规痣的 PRAME 和 HMB45 染色模式。HMB45 梯度定义为仅在浅层黑素细胞中免疫阳性。HMB45 异常表达包括浅层和深层免疫阳性。
在 20 例 NHP 中有 10 例（50%）观察到异常的 HMB45 表达。大多数常规痣显示 HMB45 染色的梯度，只有 1 例在真皮深层出现局灶性弱阳性表达（6.3%）。所有 NHP 和常规痣的病例均表现出 PRAME 免疫染色基本上为阴性。
NHP 中异常的 HMB45 表达并不罕见，可能是一个诊断陷阱。PRAME 免疫染色阴性可能是一个令人放心的发现，有助于将晕痣与恶性黑色素瘤区分开来。
