Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO.
Am J Surg Pathol. 2014 Jul;38(7):1007-12. doi: 10.1097/PAS.0000000000000205.
Adenocarcinoma of the prostate measuring <1 mm in needle core tissue can present a diagnostic challenge. The α-methylacyl-CoA racemase (AMACR) immunostain, a marker of neoplastic prostatic epithelial cells, may be used to evaluate these limited tumor cases, in needle biopsy, with a reported sensitivity ranging to a low of 80%. The use of the ERG immunostain in evaluating prostate cancer is becoming more common, but the utility of this marker in direct comparison with AMACR has not been examined. The purpose of our study was to investigate whether the ERG immunostain adds diagnostic value to AMACR expression in evaluating untreated prostate cancer foci measuring <1 mm in core needle biopsy. We identified 129 blocks from 113 patients with continuous tumor foci measuring <1 mm on core needle biopsy. ERG and AMACR immunostaining analyses were performed on serial sections from the blocks, and expression was assessed by intensity and proportion scores assigned to each stain. Sixty-five of the selected blocks from 63 patients retained tumor foci measuring <1 mm after obtaining deeper sections. Of these 65 tumor foci, 36 were positive for AMACR alone, 28 were positive for AMACR and ERG, and 1 was positive for ERG alone. AMACR had a sensitivity of 99%, and ERG had a sensitivity of 45%. Most cases displayed strong AMACR expression, and only 7 of 65 foci (11%) exhibited weak or negative AMACR expression. Of these 7 foci with weak or negative AMACR expression, only 2 foci were ERG positive. This is the first study to our knowledge that examines the diagnostic utility of ERG expression in comparison with AMACR expression in minimal usual acinar adenocarcinoma of the prostate in core needle biopsy. Our findings suggest that AMACR should be the first-line positive marker for confirmation of a diagnosis of minimal adenocarcinoma of the prostate, when needed. ERG immunohistochemistry is potentially indicated only in uncommon cases of minimal adenocarcinoma when AMACR staining is negative or weak, and in these cases ERG is informative in only a minority (29%) of cases. Evidence-based utilization of diagnostic markers, without their routine overutilization, such as ERG expression in minimal adenocarcinoma, that do not provide added diagnostic value in most cases, is an important principle in application of immunohistochemistry in this era of cost-consciousness.
前列腺腺癌在针芯组织中测量 <1 毫米时可能具有诊断挑战性。α-甲基酰基辅酶 A 消旋酶 (AMACR) 免疫染色是一种评估这些局限性肿瘤病例的标志物，在活检中报告的敏感性范围低至 80%。ERG 免疫染色在评估前列腺癌中的应用越来越普遍，但该标志物与 AMACR 的直接比较的实用性尚未得到检验。我们的研究目的是调查 ERG 免疫染色在评估未经治疗的前列腺癌病灶时是否增加了 AMACR 表达的诊断价值，这些病灶在核心针活检中测量 <1 毫米。我们从 113 名患者的 129 个块中鉴定出连续的肿瘤病灶，在核心针活检中测量 <1 毫米。对来自 113 名患者的 129 个块进行 ERG 和 AMACR 免疫染色分析，并通过为每个染色分配强度和比例评分来评估表达。在获得更深的切片后，从 63 名患者中选择的 65 个块中保留了 <1 毫米的肿瘤病灶。在这 65 个肿瘤病灶中，单独 AMACR 阳性的有 36 个，单独 AMACR 和 ERG 阳性的有 28 个，单独 ERG 阳性的有 1 个。AMACR 的敏感性为 99%，而 ERG 的敏感性为 45%。大多数病例显示出强烈的 AMACR 表达，仅有 65 个病灶中的 7 个（11%）显示出弱或阴性 AMACR 表达。在这 7 个弱或阴性 AMACR 表达的病灶中，只有 2 个病灶 ERG 阳性。这是我们所知的首次研究，比较了 ERG 表达与前列腺核心针活检中最小典型腺癌中 AMACR 表达的诊断效用。我们的研究结果表明，当需要确认最小前列腺腺癌的诊断时，AMACR 应该是首选的阳性标志物。当 AMACR 染色阴性或弱阳性时，ERG 免疫组化可能仅适用于罕见的最小腺癌病例，并且在这些病例中，只有少数（29%）病例 ERG 有信息。在这个注重成本效益的时代，在大多数情况下没有提供额外诊断价值的情况下，如在最小腺癌中常规过度使用 ERG 表达，有必要合理利用诊断标志物，而不是过度使用。
