Both classifications, Kiel and IWF, have their advantages and disadvantages, страница 8

b) in many cases chromosomal abnormalities (trisomy 3 or 5) are documented [147,148]; c) TCR gene rearrangement methods have demonstrated clonality of T cells regarding TCR-B and tcr-y chain genes [149-151]. However, in part of the cases there is an additional IgH-chain gene rearrangement [149]. Immunohistochemically the proliferating T cells (Ki-67+) are most frequently CD4 positive whereas in a minority of cases the proliferating cells show CDS positivity [149]. The latter is related to the presence of IgH chain gene rearrangement. Another histological and immunohistochemical characteristic of AILD-type lymphoma is the abundance of hyperplastic follicular dendritic cells [152] inside as well as outside the "burnt-out" germinal cells, even among the Arborizing vessels.

Although non-neoplastic, immunoreactive cases of AILD occur [144], the prognosis is generally poor, especially for cases of AILD-type T-cell lymphoma. The mean survival time was about 24 months after combined prednisone and chemotherapy [153]. It seems that the group with CDS positivity and IgH chain gene rearrangement has a relatively better prognosis [149]. In over 10% of AILD-type T-cell lymphomas transformation into high-grade malignant lymphoma of the large T-cell pleomorphic, T-immunoblastic or large cell anaplastic (Ki-1+) type occurs. The finding of light chain (k or ^) monoclonal plasma cells and immunoblasts [154,155] could be explained either as a true B-cell lymphoma or as reactive B-cell clone expansion induced by the helper activity of the CD4-positive neoplastic cell clone. Aetiopathogenetically AILD-type T-cell lymphoma has been related to viruses such as rubella [156], herpes-like [157] and Mazon-Pfizer monkey virus [158].

Pleomorphic Small T-cell Lymphoma

Although occurring also in childhood, pleomorphic small T-cell lymphoma shows its incidence peak after 60 years of age. The tumor cells may be HTLV-1 positive, especially in Japan and the Caribbean area. Histologically the lymph nodes are diffusely involved by small-sized (Fig. 11a) pleomorphic cells. Their nuclei are gyroid, indented or irregular with small nucleoli. The cytoplasm is rather scarce and pale to clear [20,120,159]. Skin involvement is common. Usually, all types of peripheral T-cell lymphomas show more mitoses than their morphological analogues among B-cell lymphomas. In addition, they frequently show epidermotropism/epitheliotropism and angiotropism. Immunohistochemically they have the phenotype of helper CD4-positive T cells (Fig. 11b). With molecular methods they reveal clone gene rearrangement for tcr-y or TCR-B. Despite the "cytic" appearance of the neoplastic cells and the initial absence of "blastic" cells, the prognosis of pleomorphic small T-cell lymphomas is poor. Neoplastic cells undergo an early activation and transformation to large cells, resulting in development of high-grade malignant T-cell lymphoma. Pleomorphic small T-cell lymphoma is rather difficult to be categorized in the IWF.