Miettinen M, Lasota J
Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
Mod Pathol. 1995 Sep;8(7):769-74.
Merkel cell carcinoma and malignant lymphoma are important differential diagnoses for undifferentiated cutaneous round cell tumors and immunohistochemistry is instrumental in their evaluation. We describe a case of a 73-year-old man who had cutaneous large cell lymphoma in the right leg (immunophenotype CD45+, CD19+, CD20+ CD22+, lambda clonal, cytokeratin-, NSE-) and lymphoma in left leg simulating Merkel cell carcinoma showing absence of leukocyte antigens (CD45-, CD20-, no light chains) and focal expression of keratin and NSE. However, analysis of polymerase chain reaction amplification products of DNA extracted from both lesions showed two amplifiable sharp bands indicating clonal rearrangements of both alleles of the immunoglobulin heavy chain. Cloning and sequencing of the products from left and right leg lesions showed either 100% homology (one band), or close similarity (the other band), indicating that both tumors were derived from the same B-cell lymphoma clone. This case shows the value of polymerase chain reaction and sequencing in analyzing the ultimate nature of lymphoproliferations and illustrates the potential limitations of immunophenotyping.
默克尔细胞癌和恶性淋巴瘤是未分化皮肤圆形细胞瘤的重要鉴别诊断，免疫组织化学在其评估中发挥着重要作用。我们报告一例73岁男性病例，其右腿患有皮肤大细胞淋巴瘤（免疫表型为CD45 +、CD19 +、CD20 +、CD22 +、λ克隆、细胞角蛋白阴性、神经元特异性烯醇化酶阴性），左腿淋巴瘤模拟默克尔细胞癌，表现为白细胞抗原缺失（CD45 -、CD20 -、无轻链），细胞角蛋白和神经元特异性烯醇化酶呈局灶性表达。然而，对从两个病变部位提取的DNA进行聚合酶链反应扩增产物分析，显示出两条可扩增的清晰条带，表明免疫球蛋白重链的两个等位基因均发生了克隆性重排。对左腿和右腿病变产物进行克隆和测序，结果显示要么100%同源（一条带），要么高度相似（另一条带），表明这两种肿瘤均源自同一个B细胞淋巴瘤克隆。该病例显示了聚合酶链反应和测序在分析淋巴增殖性病变最终性质方面的价值，并说明了免疫表型分析的潜在局限性。
