Unusual soft tissue tumors

Abstract

In this session, the detailed clinicopathological and genetic findings, and the differential diagnosis of the following five unusual soft tissue tumors will be demonstrated. 1) Inflammatory myofibroblastic tumor occurs in abdominal soft tissue, GI tract, and lung of children and young adult. The prediction of biological behavior is difficult. Cytogenetic study demonstrates ALK rearrangement in more than half cases. 2) Pseudomyogenic hemangioendothelioma is rarely metastasizing endothelial neoplasm. It was initially named as epithelioid sarcoma-like hemangioendothelioma and mimicking myoid tumor or epithelioid sarcoma. FLI1 and ERG are useful markers for this tumor. 3) Myoepithelioma predominantly involve lower or upper limb of young to middle aged adult. This intermediate tumor have broad spectrum of biological behavior, according to cytological atypia. 45% of the tumor shows EWSR1 rearrangement. 4) Malignant rhabdoid tumor is very aggressive tumor and it arises in the deep axial location, such as neck and paravertebral region of infants and children. Tumor cells show the loss of SMARCB1/INI1 protein expression and its gene alterations. 5) PEComa predominantly affects retroperitoneum, uterus and GI tract of female. Definitive criteria of malignant PEComa has not been established yet. The tumor with malignant histology shows aggressive biological behavior.