Internal Medicine
Online ISSN : 1349-7235
Print ISSN : 0918-2918
ISSN-L : 0918-2918
Amelanotic Malignant Melanoma of Unknown Primary Origin Metastasizing to the Bone Marrow: A Case Report and Review of the Literature
Tomotaka SuzukiShigeru KusumotoShinsuke IidaToyohiro TadaFumiko Mori
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2014 Volume 53 Issue 4 Pages 325-328


We herein describe the case of a 77-year-old Japanese man who presented with progressive thrombocytopenia. No lymphadenopathies, bone lesions, hepatosplenomegaly or masses within any internal organs were detectable. Bone marrow smears revealed diffuse infiltration of large atypical cells morphologically resembling mature lymphoid neoplasms. A flow cytometric analysis showed that the tumor cells strongly expressed CD56 without myeloid or lymphoid antigens, suggesting that they were non-hematologic in origin. Ultimately, amelanotic malignant melanoma of unknown primary origin was diagnosed based on positive immunostaining for S100 proteins, HMB-45 and Melan-A. This case illustrates the usefulness of flow cytometric analyses for making such diagnoses. We also review the available literature on similar cases.

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© 2014 by The Japanese Society of Internal Medicine
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