title: Malignant Melanoma With Osteoclast-Like Differentiation.
abstract: Osteoclast-like giant cells are frequently encountered in nonskeletal malignancies; however, the evidence to date suggests that they represent a tissue response to the lesion rather than neoplastic differentiation. We describe a case of metastatic melanoma demonstrating osteoclast-like differentiation in the lung. The lung nodule was diagnosed as a metastatic melanoma by histological features and confirmed by immunohistochemistry. Resection specimen showed numerous multinucleated giant cells exhibiting osteoclast-like morphology dispersed throughout the lesion. Both the neoplastic melanocytes and giant cells were reactive for HMB-45, Melan-A, and S100. In addition, the multinucleated neoplastic giant cells were also reactive for the monocyte/macrophage lineage markers CD68 and CD163, and alkaline phosphatase, an enzyme present in normal osteoclasts. The neoplastic melanocytes and the multinucleated neoplastic giant cells were also reactive for microphthalmia-associated transcription factor, a protein required for the development of both melanocytes and osteoclasts. Collectively, a co-expression of monocyte/macrophage markers along with melanocytic markers and alkaline phosphatase in the multinucleated neoplastic giant cells in metastatic melanoma suggest that malignant melanocytes are capable of differentiating into osteoclast-like cells and consequently aid invasion into various structures and eliciting the aggressive behavior.
authors.affiliation: The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Jason K
authors.initials: JK
authors.lastname: Wasserman
authors.affiliation: The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Harmanjatinder S
authors.initials: HS
authors.lastname: Sekhon
authors.affiliation: The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada yayroud@toh.on.ca.
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Ayroud
mesh_terms: D002454:Cell Differentiation; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000556:secondary*; D008297:Male; D008545:Melanoma / Q000473:pathology / Q000556:secondary*; D008875:Middle Aged; D010010:Osteoclasts / Q000473:pathology*; D012878:Skin Neoplasms / Q000473:pathology*
keywords: differentiation; malignant melanoma; melanocytes; osteoclast-like tumor giant cells