Investigation for neoplastic myoepithelial cells in pleomorphic adenomas and myoepitheliomas-Histopathlogical and immunohistochemical valuations-

确定肿瘤性肌上皮瘤的鉴别标准对涎腺肿瘤的正确分类至关重要。在甲醇固定的多形性腺瘤中，（PA ; n=14）和肌上皮瘤（MYO ;对6例PA和2例MYO进行了MSA的免疫电镜（IEM）检查。MSA和细胞角蛋白14（CK 14）明显减少，在PA的非腔细胞和肿瘤细胞MY中检测到正常肌上皮细胞的两种标志物，比预期的要多;只有5/14的PA（36%）和2/5的MYO（40%）具有显著数量（范围为5-80%）的阳性肿瘤细胞。CK 14的表达也是有限的（50%的PA和40%的MYO分别有10-70%和10-40%的细胞阳性）。Vimentin呈强烈弥漫性在所有PA和MYO中（90-100%的细胞）表达，而在93%的PA中观察到GFAP（25-100%细胞阳性）和100% MYO常规电镜下，PA和MYO中只有1/3的肿瘤细胞有少量肌丝，（仅在一个MYO中这些是中等突出的），而IEM（n=8）在2个PA和1个MYO中显示了MSA-胶体金阳性肌丝，所有这些都通过常规EM显示缺乏肌丝。当生长模式和细胞类型指示PA或MYO的诊断时，通过免疫组织化学或EM的肌丝检测的缺乏不排除PA或MYO的诊断; IEM显示即使在肌丝明显缺失或通过常规EM最小时也可以检测到肌肌动蛋白。波形蛋白和GFAP是比肌动蛋白和CK 14更一致的肿瘤性肌上皮细胞的标记物。

Determining criteria for identifying neoplastic myoepithlium is criticalfor proper classification of salivary gland tumors. Muscle-specific actin (MSA) and intermediate filament expression were determined in methanol-fixed pleomorphic adenomas (PA ; n=14) and myoepithliomas (MYO ; N=5), as well as myofilament formation in electron micrographs of 22 PA and 10 MYO.Immunoelectron microscopy (IEM) for MSA was performed on 6 PA and 2 MYO.Considerably less MSA and cytokeratin 14 (CK14), two markers for normal myoepithlial cells, were detected in nonluminal cells of PA and tumor cells MY than expected ; only 5/14 PA (36%) and 2/5 MYO (40%) had significant numbers (ranging from 5-80%) of positive tumor cells. Expression of CK14 was also limited (50% of PA and 40% of MYO with 10-70% and 10-40% cells positive, respectively). Vimentin was strongly and diffusely (90-100% of cells) expressed in all PA and MYO,while GFAP was noted in 93% of PA (25-100% cells positive) and 100% of MYO (10-60% cells positive).By routine EM,only one-third of PA and MYO had small numbers of tumor cells with myofilaments (in only one MYO were these moderately prominent), while IEM (n=8) revealed MSA-colloidal gold positive myofilaments in 2 PA and 1 MYO,all of which appeared to lack myofilaments by routine EM.Clearly, the lack of myofilament detection by immunohistochemistry or EM does not exclude a diagnosis of PA or MYO when growth patterns and cell type indicate such a diagnosis ; this even applies to plasmacytoid MYO.IEM shows muscle-actin can be detected even when myofilaments are apparently absent or minimal by routine EM.Vimentin and GFAP are more consistent markers for neoplastic myoepithelial cells than actin and CK14.