Skin and superficial soft tissue neoplasms with multinucleated giant cells: Clinical, histologic, phenotypic, and molecular differentiating features

Multinucleated giant cells (MGC) are commonly seen in an array of neoplastic and non-neoplastic conditions, to include: granulomatous dermatitis, fibrohistiocytic lesions such as xanthogranulomas, and soft tissue tumors such as giant cell tumors of soft tissue. In addition, multinucleated giant cells are infrequently seen in melanoma, squamous cell carcinoma, and atypical fibroxanthoma. There are many different types of MGCs and their presence, cytologic, and immunohistochemical features within these pathologic entities vary. Thus, correct identification of the different types of MGCs can aid the practicing pathologist in making the correct diagnosis of the overall pathologic disease. The biologic diversity and variation of MGCs is currently best exemplified in cytologic appearance and immunohistochemical profiles. However, much remains unknown about the origination and evolution. In this review, we i) reflect on the various types of MGCs and the current understanding of their divergent development, ii) describe the histologic, immunohistochemical, and molecular (if previously reported) differentiating features of common skin and superficial soft tissue neoplasms that may present with multinucleated giant cells.