Shih I M, Kurman R J
Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-6917, USA.
Lab Invest. 1996 Sep;75(3):377-88.
Melanoma cell adhesion molecule (Mel-CAM), also known as MUC18, is a cell adhesion molecule belonging to the immunoglobulin supergene family. Because of the importance of cell adhesion molecules in trophoblastic function and development, we studied the immunohistochemical distribution of Mel-CAM in trophoblastic cells in the implantation site and the normal placenta and compared it with a variety of gestational trophoblastic lesions. Formalin-fixed paraffin-embedded tissues from 44 normal placentas, 54 implantation sites (37 normal and 17 exaggerated), 13 hydatidiform moles, 13 placental site trophoblastic tumors (PSTT), and 16 choriocarcinomas were evaluated for Mel-CAM expression in trophoblast using a Mel-CAM-specific polyclonal antibody and an immunoperoxidase method. Mel-CAM was demonstrated in intermediate trophoblastic (IT) cells in all normal placentas, implantation sites, and exaggerated placental sites. Mel-CAM staining was also found in all the multinucleated IT cells in the placental site. In contrast, Mel-CAM was not detected in either cytotrophoblast (CT) or syncytiotrophoblast (ST). Similarly, in hydatidiform moles, Mel-CAM was confined to IT. In trophoblastic neoplasms, Mel-CAM was expressed in all 13 placental site trophoblastic tumors, and in 14 of 16 (88%) choriocarcinomas. Mel-CAM staining was localized to IT in both placental site trophoblastic tumors and in choriocarcinomas. In conclusion, Mel-CAM is a specific and sensitive marker for IT differentiation in normal placentas, implantation sites, and in gestational trophoblastic lesions. The differential staining pattern of Mel-CAM provides support for a dual pathway of trophoblastic differentiation in the normal placenta and in gestational trophoblastic lesions in which CT differentiates directly into ST on the villous surface, compared with the differentiation of CT to IT and then into multinucleated IT cells in extravillous sites. In view of the difficulty in distinguishing IT from CT by conventional light microscopy, it is proposed that IT cells be defined on the basis of both their morphologic features and immunophenotype as a mononucleate trophoblastic cell that expresses Mel-CAM.
黑色素瘤细胞黏附分子（Mel-CAM），也称为MUC18，是一种属于免疫球蛋白超基因家族的细胞黏附分子。鉴于细胞黏附分子在滋养层功能和发育中的重要性，我们研究了Mel-CAM在着床部位和正常胎盘的滋养层细胞中的免疫组织化学分布，并将其与各种妊娠滋养层病变进行比较。使用Mel-CAM特异性多克隆抗体和免疫过氧化物酶方法，对44例正常胎盘、54个着床部位（37个正常和17个过度增生）、13例葡萄胎、13例胎盘部位滋养层肿瘤（PSTT）和16例绒毛膜癌的福尔马林固定石蜡包埋组织进行滋养层中Mel-CAM表达的评估。在所有正常胎盘、着床部位和过度增生的胎盘部位的中间滋养层（IT）细胞中均检测到Mel-CAM。在胎盘部位的所有多核IT细胞中也发现Mel-CAM染色。相比之下，在细胞滋养层（CT）或合体滋养层（ST）中均未检测到Mel-CAM。同样，在葡萄胎中，Mel-CAM局限于IT。在滋养层肿瘤中，Mel-CAM在所有13例胎盘部位滋养层肿瘤以及16例绒毛膜癌中的14例（88%）中表达。Mel-CAM染色在胎盘部位滋养层肿瘤和绒毛膜癌中均定位于IT。总之，Mel-CAM是正常胎盘、着床部位和妊娠滋养层病变中IT分化的特异性和敏感标志物。Mel-CAM的差异染色模式支持正常胎盘和妊娠滋养层病变中滋养层分化的双途径，其中CT在绒毛表面直接分化为ST，而在绒毛外部位CT分化为IT，然后再分化为多核IT细胞。鉴于通过传统光学显微镜难以将IT与CT区分开来，建议根据其形态学特征和免疫表型将IT细胞定义为表达Mel-CAM的单核滋养层细胞。
