Anaplastic lymphoma kinase expression as a marker of malignancy Application to a case of anaplastic large cell lymphoma with huge granulomatous reaction

Anaplastic large cell lymphoma (ALCL) shows a wide morphologic spectrum, in cluding the occurrence of reactive components obscuring the neoplastic popu lation. This makes its distinction from hyperimmune reaction difficult. The authors describe an ALCL in a girl who had a tick bite 20 days prior to cl inical presentation. She developed a huge epithelioid reaction (an unpreced ented finding for this tumor). The diagnostic controversies were solved by applying the ALKc antibody against anaplastic large cell lymphoma kinase (A LK), in conjunction with reagents anti-nucleophosmin (NPM), which showed th e typical staining pattern observed in ALCL carrying t(2;5). Comprised with in the epithelioid component there were large anaplastic cells and small-me dium sized atypical elements displaying strong nuclear and cytoplasmic posi tivity for ALK and NPM (N-terminal region). This pattern, never observed in normal lymphocytes, corresponds to the presence of the product of the hybr id gene NPM/ALK produced by t(2;5). Following the diagnosis, the patient - whose general conditions were critical - underwent aggressive chemotherapy, achieving complete remission. (C) 2000, Ferrata Storti Foundation.