ATF1 and neoplasm: <h4>Background</h4>Intracranial mesenchymal tumors are a rare type of neoplasm (0.3% of all soft tissue tumors) characterized by a fusion of a <i>FET</i> family gene (usually <i>EWSR1</i>, rarely <i>FUS</i>) to <i>CREB</i> family genes (<i>CREB1, ATF1</i>, and <i>CREM</i>) with a slow-growing and favorable prognosis.