Malignant histiocytosis: a case report of a rare tumour presenting with spontaneous splenic rupture.

Malignant histiocytosis is a rare invasive proliferation of neoplastic histiocytes. Cases previously reported as malignant histiocytosis were shown to be lymphomas of T or B lineage, especially anaplastic large-cell lymphomas. A case of malignant histiocytosis is described, in which a patient presenting with symptoms suggestive of pneumonia suddenly deteriorated and died. At autopsy, a large quantity of fresh blood, originating from several ruptured nodules on the enlarged spleen, was seen in the peritoneal cavity. Extensive infiltration by pleomorphic tumour cells and erythrophagocytosis by tumour cells were seen on histological examination of the spleen. Immunohistochemical analysis and staining were carried out. This is the second reported case of malignant histiocytosis presenting with spontaneous splenic rupture.