F13A1 and neoplasm: Immunohistochemically, the tumor cells showed cytoplasmic staining for factor XIIIa and ALK (the ALK staining was performed using both clone 5A4 (NICHIREI) (Fig. 5a) and an anti-ALK-1 antibody (DAKO) (Fig. 5b)), but were negative for AE1/AE3 keratin, alpha-smooth muscle actin, CD30, CD34, CD68, PU.1, melan A, MITF, and S-100 protein.