Biernacka Anna, Linos Konstantinos D, DeLong Peter A, Suriawinata Arief A, Padmanabhan Vijayalakshmi, Liu Xiaoying
Address: Department of Pathology and Laboratory Medicine, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon.
Address: Department of Pathology and Laboratory Medicine, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon; Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
Cytojournal. 2016 Sep 20;13:21. doi: 10.4103/1742-6413.190914. eCollection 2016.
When confronted with a metastatic poorly differentiated tumor of unknown origin, the initial workup includes the standard panel of immunostains to rule out carcinoma, sarcoma, lymphoma, and the greatest mimicker in pathology - malignant melanoma. Although not specific, the S-100 protein is expressed in over 95% of malignant melanomas. Herein, we present a case of multiorgan metastatic malignancy with a dominant hilar and mediastinal mass in a current smoker; clinically, highly suggestive of widespread primary lung cancer. This case was eventually classified as malignant melanoma, despite a significant diagnostic challenge due to lack of prior history, unusual cytomorphology, and S-100 protein negativity. A battery of immunostains was performed and the addition of other melanocytic-associated markers confirmed the melanocytic lineage of the neoplasm. This case highlights the pitfalls in the differential diagnosis of a metastatic tumor of unknown origin by fine needle aspiration cytology due to the significant morphologic overlap of poorly differentiated malignancies. We emphasize that, albeit rare, malignant melanomas can be completely negative for S-100 protein and the use of additional melanocytic-associated markers in the differential workup maybe critical in arriving promptly at a proper diagnosis. We also briefly discuss other currently available immunohistochemical markers that can assist in the identification of the S-100 negative melanoma.
当面对一个来源不明的转移性低分化肿瘤时，初始检查包括一系列标准免疫染色，以排除癌、肉瘤、淋巴瘤以及病理学上最易混淆的疾病——恶性黑色素瘤。尽管不具有特异性，但S-100蛋白在超过95%的恶性黑色素瘤中表达。在此，我们报告一例现吸烟者发生的多器官转移性恶性肿瘤，以肺门和纵隔肿块为主；临床上，高度提示广泛的原发性肺癌。尽管由于缺乏既往病史、不寻常的细胞形态学以及S-100蛋白阴性导致诊断面临重大挑战，但该病例最终被诊断为恶性黑色素瘤。进行了一系列免疫染色，添加其他黑色素细胞相关标志物证实了肿瘤的黑色素细胞谱系。该病例突出了细针穿刺细胞学在鉴别诊断来源不明的转移性肿瘤时的陷阱，因为低分化恶性肿瘤在形态学上有显著重叠。我们强调，尽管罕见，但恶性黑色素瘤可能S-100蛋白完全阴性，在鉴别诊断中使用其他黑色素细胞相关标志物对于迅速做出正确诊断可能至关重要。我们还简要讨论了目前其他可用于辅助识别S-100阴性黑色素瘤的免疫组化标志物。
