Embryonal (undifferentiated) sarcoma of the liver with peripheral angiosarcoma differentiation arising in a mesenchymal hamartoma in an adult patient.

Embryonal (undifferentiated) sarcoma of the liver (ESL) is a rare malignant neoplasm composed of undifferentiated sarcomatous tissue. We are presenting a case of a 74-year-old woman diagnosed with an ESL arising from a mesenchymal hamartoma of the liver (MHL). Both lesions occur typically in childhood, with only rare reported cases in adults. Histologically, the mass consisted primarily of loose myxoid stroma admixed with bland spindle cells and extensive, cystic (lymphangioma-like) degeneration. However, also present peripherally were markedly atypical cells (including multi-nucleated forms) and hyaline globules. Additionally, atypical cells with a sinusoid tectorial growth pattern were identified, which were positive for CD31, CD34 and Factor VIII. The tumor cells of ESL are classically described as being negative for tissue-specific immunohistochemical markers. However our case demonstrated focal positivity for vascular markers CD31, CD34 and Factor VIII and this along with the sinusoidal tectorial growth pattern, mimicked an angiosarcoma.