ALK and gastrointestinal stromal tumor: A panel of antibodies (Table I) was used to evaluate the tumor samples for the presence of smooth muscle [Desmin and smooth muscle actin (SMA)], fibroblastic/myofibroblastic (SMA), schwannian (S-100) and epithelial cell (AE1/AE3) differentiation, and various immunohistochemical markers typically expressed in GI stromal tumors [GIST; discovered on GIST (DOG) 1, cluster of differentiation (CD) 117, CD34], inflammatory myofibroblastic tumors [anaplastic lymphoma kinase (ALK)], aggressive fibromatosis (β-catenin) and immunoglobulin (Ig) G4-associated disease (IgG4, IgG).