Background: Coincidence of various neoplasias in the same patients, as well as a hereditary predisposition to development of malignant neoplasms, arouses the interest of both geneticists and oncologists. Case Report: The paper presents a case of a 2-year-old girl, in whom two foci of Langerhans cell histiocytosis in the left parietal bone and right humerus were diagnosed 5 months after completion of chemotherapy with etoposide, ifosfamide and cisplatin combined with surgical resection of a malignant germ cell tumor of the sacrococcygeal region. Both histiocytosis foci were removed surgically. No relapses of either disease have been observed within 24 months after the completion of treatment. Laboratory tests reveal persistent increase of alkaline phosphatase level. Conclusions: A rare case of coincident two independent neoplastic processes – malignant germ cell tumor and Langerhans cell histiocytosis in a child is presented. Despite good treatment results obtained for both diseases, the follow-up period has been short and the child requires further clinical observation.

Keywords: germ cell tumor, langerhans cell histiocytosis, Association