Abstract: Objective : 33 autopsy cases of previously diagnosed malignant histiocytosis were investigated to the tumor cell lineage, Epstein -Barr virus infection and clinicopathological features. Methods : With tissue microarray technique, different tissues from paraffin embedded tissue blocks of each case were integrated into one paraffin block. Then according routing method, multitissue sections were prepared for next immunostaining and in situ hybridization. Using LsAB method, immunohisto-chemical stainings were performed. The applied antibodies were as follows: CD4, CD8, CD20, CD45RO,CD56, CD3ε, CD30, CD68, TIA-1 and granzyme B. A DNA-RNA in situ hybridization was used for detection of mRNA encoded by EBY (EBER1/2). Results : 4 cases were deleted from the 33 cases according to the results of immunostainings. In the remaining 29 cases, 28 cases were peripheral T-cell lymphoma, in which 3 were subcutaneous panniculitis like T cell lymphoma, 1 was intestinal T cell lymphoma, and 1 was anaplastic large cell lymphoma. There were 16 of 28 T cell lymphomas with E-BER1/2 positive reactions. There was one case of intravascular large B -cell lymphoma. Conclusions :In cell lineage, so called malignant histiocytosis is a group of heterogeneous disorders. In our study most cases represented cytotoxic cell lymphomas (28/29), only one came from B cell, and none of them from monocyte/macrophage.