Nandedkar M A, Palazzo J, Abbondanzo S L, Lasota J, Miettinen M
Department of Hematopathology, Armed Forces Institute of Pathology, Washington, DC 20306-6000, USA.
Mod Pathol. 1998 Dec;11(12):1204-10.
Leukocyte common antigen (CD45/LCA) and keratin expression are generally mutually exclusive in diagnostic surgical pathology. CD45 reactivity is a reliable indicator of the hematolymphoid nature of a tumor, whereas keratin reactivity is typical of epithelial differentiation (carcinomas and some sarcomas). Some lymphomas, however, might lack detectable CD45 expression, whereas occasional ones might express keratins. CD45 immunoreactivity has been considered exquisitely specific for hematopoietic cells. We report three undifferentiated or neuroendocrine carcinomas that showed membrane-associated immunoreactivity for CD45 in addition to showing distinctive keratin cocktail (AE1/AE3) and epithelial membrane antigen reactivity (all cases); also, keratin 7 was demonstrated in one case and keratin 19 in another. Two cases were lymph node metastases of undifferentiated carcinomas, one of them from the lungs and the other of an unknown origin; the former case showed neuroendocrine features. The third case represented a pulmonary large-cell undifferentiated carcinoma. These cases were negative for lineage-specific leukocyte antigens and did not show clonal immunoglobulin heavy-chain gene rearrangements. Electron microscopic studies demonstrated desmosomes and keratin-like tonofilaments in all three cases, thus confirming the epithelial nature of these tumors. The exceptional membrane staining for CD45 seen in these undifferentiated carcinomas might be comparable to experimentally detected incorporation of leukocyte antigens into the cell membranes of nonleukocytic cells in a leukocyte-rich environment. This rare diagnostic pitfall should be considered in the diagnostic surgical pathology of undifferentiated tumors. It is best avoided by employing a panel of leukocyte and epithelial antigens and by use of electron microscopy, if possible.
在诊断性外科病理学中，白细胞共同抗原（CD45/LCA）和角蛋白表达通常相互排斥。CD45反应性是肿瘤血液淋巴性质的可靠指标，而角蛋白反应性是上皮分化（癌和一些肉瘤）的典型表现。然而，一些淋巴瘤可能缺乏可检测到的CD45表达，而偶尔有淋巴瘤可能表达角蛋白。CD45免疫反应性一直被认为对造血细胞具有高度特异性。我们报告了三例未分化或神经内分泌癌，这些肿瘤除了显示独特的角蛋白组合（AE1/AE3）和上皮膜抗原反应性（所有病例）外，还显示出与膜相关的CD45免疫反应性；此外，其中一例显示角蛋白7，另一例显示角蛋白19。两例为未分化癌的淋巴结转移，其中一例来自肺部，另一例来源不明；前一例显示神经内分泌特征。第三例为肺大细胞未分化癌。这些病例对谱系特异性白细胞抗原呈阴性，且未显示克隆性免疫球蛋白重链基因重排。电子显微镜研究在所有三例中均显示有桥粒和角蛋白样张力丝，从而证实了这些肿瘤的上皮性质。在这些未分化癌中见到的CD45异常膜染色可能类似于在富含白细胞的环境中实验检测到的白细胞抗原掺入非白细胞细胞膜的情况。在未分化肿瘤的诊断性外科病理学中应考虑这种罕见的诊断陷阱。如果可能的话，最好通过使用一组白细胞和上皮抗原以及电子显微镜来避免这种情况。
