KRAS and lymphoma: However, neoplastic cells were distinguished by the exclusivity of the rearrangement of TCR genes within the lymphoma cells, whereas mutations in the KRAS and TP53 genes selectively affected some monocytes and histiocytic cells, contrasting with the great majority of reported cases where T cell lymphoproliferative disorders and secondary/ synchronous associated malignant histiocytosis shared the same TCR gene rearrangement.