El Shabrawi-Caelen Laila, Kerl Helmut, Cerroni Lorenzo
Department of Dermatology, University of Graz, 8036 Graz, Austria.
Am J Dermatopathol. 2004 Oct;26(5):364-6. doi: 10.1097/00000372-200410000-00003.
Pigmented actinic keratosis is one of the simulators of early melanoma in situ from severely sun-damaged skin. Close scrutiny of the hematoxylin and eosin stained section does not always allow an unequivocal diagnosis, because it is sometimes difficult to distinguish pigmented keratinocytes from melanocytes. Immunohistochemical stains, such as S-100 and HMB-45, are used routinely to address this problem. Melan-A, also known as MART-1, is an additional melanocytic marker and has proved to be useful in identifying metastatic tumors of melanocytic origin. The usefulness of this marker to discriminate pigmented actinic keratosis from early melanoma in situ, however, has not yet been a subject of investigation. In this study we evaluated Melan-A expression in ten unequivocal cases of pigmented actinic keratosis and compared the staining pattern with that of S-100, HMB-45, and tyrosinase. In all ten cases the number of cells highlighted with Melan-A was by far larger than those labeled with S-100, HMB-45, and tyrosinase. Four cases showed clusters of Melan-A positive cells being suggestive of melanocytic nests. Even areas of normal skin adjacent to the actinic keratosis featured prominent staining of Melan-A, but only inconsistent labeling of intraepidermal melanocytes with S-100, HMB-45, and tyrosinase. We therefore believe that Melan-A is a more sensitive marker for intraepidermal melanocytes than S-100, HMB-45, and tyrosinase. In addition there may be expression of Melan-A in keratinocytes and nonmelanocytic cells. To avoid an erroneous diagnosis of malignant melanoma one should therefore interpret results obtained from Melan-A stained slides carefully and in the context with other melanocytic markers.
色素性光化性角化病是严重日光损伤皮肤中早期原位黑色素瘤的模拟病变之一。苏木精和伊红染色切片的仔细检查并不总能做出明确诊断，因为有时很难将色素性角质形成细胞与黑素细胞区分开来。免疫组织化学染色，如S-100和HMB-45，常用于解决这个问题。Melan-A，也称为MART-1，是另一种黑素细胞标志物，已被证明在识别黑素细胞起源的转移性肿瘤方面很有用。然而，该标志物用于区分色素性光化性角化病与早期原位黑色素瘤的实用性尚未成为研究课题。在本研究中，我们评估了Melan-A在10例明确的色素性光化性角化病病例中的表达，并将染色模式与S-100、HMB-45和酪氨酸酶的染色模式进行了比较。在所有10例病例中，Melan-A突出显示的细胞数量远远多于用S-100、HMB-45和酪氨酸酶标记的细胞数量。4例显示Melan-A阳性细胞簇，提示黑素细胞巢。即使是光化性角化病附近的正常皮肤区域，Melan-A也有明显染色，但表皮内黑素细胞用S-100、HMB-45和酪氨酸酶的标记仅不一致。因此，我们认为Melan-A比S-100、HMB-45和酪氨酸酶是表皮内黑素细胞更敏感的标志物。此外，角质形成细胞和非黑素细胞中可能存在Melan-A表达。因此，为避免错误诊断为恶性黑色素瘤，应仔细解读Melan-A染色玻片获得的结果，并结合其他黑素细胞标志物进行分析。
