The authors report a case of malignant histiocytosis, with sub acute evolution and fatal outcome in a 36 year old male, presenting with fever, hemoptysis, splenomegaly, parietal mass, anemia and bilateral pulmonary nodules. Despite one transbronchial pulmonary biopsy non diagnostic, both myelogram and histology of parietal tumor aroused the suspicion of malignant histiocytosis, later confirmed through a bronchoalveolar lavage. We didn't find any other case yet published in portuguese literature.