[T and NK cell peripheral tumors]

Peripheral T lymphomas are formed by cells with CD3 antigen which contain TCR alpha/beta. A minor part of the non-tumourous population contains TCR gamma/delta. The position is similar in T cell tumours. In the tumours however TCR may be lacking .NK ("natural killer") cells are CDR3 negative, rearrangement of the gene TCR does not occur and they are TCR alpha/beta and TCR gamma/delta negative. Contrary to T cells they contain antigen CD56 ("NK-associated antigen"). In these cells and in tumours cytotoxic proteins are usually present: TIA-1, granzyme-B, perforin. There is a continuous transition between T and NK cells. The prognosis of T cell tumours cannot be assessed from the cell size. T/NK small cell lymphomas are highly aggressive tumours. The prognosis of patients is very bad. From the morphological aspect they can resemble very much non-tumorous lymphocytes. Conversely, large cell T lymphomas of the skin which are CD30 positive take a very mild course and their prognosis is favourable. The author mentions also some more recent entities of extra-nodular T lymphomas: angiocentric NK/T lymphoma of the nose (and other regions), malignant T cell lymphoma in enteropathies, T cell lymphoma resembling subcutaneous panniculitis, hepatosplenic gamma/delta T lymphoma. These tumours are rare in this country and some, e.g. T/NK lymphoma of the nose, are found usually only in certain regions of the world. They may be however encountered also in Europe, in particular in immunosuppressed subjects and patients after organ transplantation.