TY - JOUR
T1 - A case of S-100 negative melanoma
T2 - A diagnostic pitfall in the workup of a poorly differentiated metastatic tumor of unknown origin
AU - Biernacka, Anna
AU - Linos, Konstantinos
AU - Delong, Peter
AU - Suriawinata, Arief
AU - Padmanabhan, Vijayalakshmi
AU - Liu, Xiaoying
N1 - Publisher Copyright:
© 2018 Medknow Publications. All rights reserved.
PY - 2016
Y1 - 2016
N2 - 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.
AB - 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.
KW - Malignant melanoma
KW - S-100
KW - melanocytic-associated markers
KW - poorly differentiated metastatic tumor of unknown origin
UR - http://www.scopus.com/inward/record.url?scp=85028818563&partnerID=8YFLogxK
U2 - 10.4103/1742-6413.190914
DO - 10.4103/1742-6413.190914
M3 - Article
AN - SCOPUS:85028818563
VL - 13
JO - CytoJournal
JF - CytoJournal
SN - 0974-5963
IS - 1
M1 - 21
ER -