ATF1 and clear cell sarcoma: ATF1 encodes for a cyclic AMP protein responsive element which is constitutively product after the translocation with EWRS1.4 This fusion with the partenaire ATF1, however, is not specific for myxoid sarcoma, since it is also found in clear cell sarcoma and angiomatoid fibrous histiocytoma.2–5 The differential diagnosis is mainly pulmonary mesenchymal chondrosarcoma and other myxoid tumours, as myxoid liposarcoma.6 7