Angiosarcoma with Osteoclast-Like Giant Cells: A Rare Presentation and Review of Literature

Abstract Introduction/Objective Diagnosing angiosarcoma can be challenging, especially in cases with atypical morphology. For the unsuspecting pathologist, some histopathologic features can be misleading, especially when presenting as the predominant component of a tumor or in unusual locations. Herein, we describe an osteoclast-like giant cell-rich angiosarcoma, which initially presented as a groin mass followed by pulmonary metastasis. Methods/Case Report A 54-year-old woman presented with a golf ball size mass near her right groin that she noticed 1 year ago. MRI demonstrated a heterogeneous complex mass with solid and cystic components within the right gracilis muscle. Following the diagnosis of poorly differentiated malignant neoplasm on biopsy, the patient underwent wide excision. Histopathologic examination revealed epithelioid to “rhabdoid-like” cells arranged in a fascicular pattern interspersed with osteoclast-like giant cells. Immunohistochemical stains showed tumor cells are positive for vimentin, CD10, CD31 (focal), CD99 (focal), while negative for Desmin, CD34, SMA, AE1AE3, HMB45, ALK1, CD30, S100, and Melan-A. CD68 highlighted only osteoclast-like giant cells. The lesion was diagnosed as undifferentiated pleomorphic sarcoma (UPS). Nine months later, chest CT showed a 1.3 cm lung nodule. The resected nodule was immunohistochemically and morphologically similar to the groin mass, including the presence of osteoclast-like giant cells. In addition, tumor cells were also diffusely positive for ERG and FLI1. Results (if a Case Study enter NA) NA Conclusion To our knowledge, this is the first report of soft tissue angiosarcoma with osteoclast-like giant cells presenting with lung metastasis. A high index of suspicion for an angiosarcoma in tumors occurring in proximal sites, characterized by epithelioid to “rhabdoid-like” cells, despite the presence of many osteoclast-like giant cells, is crucial to avoid misdiagnosis. Awareness of this histopathologic pattern and diagnostic confirmation with necessary immunohistochemical stains is important to avoid misinterpretation. UPS is essentially a diagnosis of exclusion, which should only be considered following extensive workup to eliminate all other possibilities.