Diffuse lung involvement by metastatic tumor from an unknown primary site often constitutes a diagnostic dilemma. Although cytologic features and pattern of metastatic spread can guide in narrowing the list of possible primary neoplasms, immunohistochemistry remains pivotal in determining the phenotype of metastatic disease. We report a case with extensive involvement of lung parenchyma by a metastatic epithelioid neoplasm exhibiting a variety of distinctive patterns with a predominance of intra-arterial and lymphangitic spread. Immunohistochemical studies showed no evidence of epithelial, melanocytic, or lymphoid differentiation. The neoplastic cells were strongly positive for vimentin and CD31 but negative for CD34 and factor VIIIR:Ag. Electron microscopy of formalin-fixed tissue revealed multiple Weibel-Palade bodies and pinocytosis, supporting the diagnosis of epithelioid angiosarcoma. Doppler studies performed after pathologic diagnosis was rendered demonstrated 2 discrete hypoechoic masses within the medial aspect of the left proximal calf musculature, suggestive of solid soft tissue neoplasm-a possible source of pulmonary metastatic disease.