Both classifications, Kiel and IWF, have their advantages and disadvantages, страница 3

Chronic lymphocytic leukemia of T-cell type (T-CLL)

In T-CLL the lymph nodes are less pronounced and the spleen enlargement is more prominent than in B-CLL. The bone marrow is not always infiltrated while skin involvement is frequent. The diffusely infiltrated lymph nodes show proliferation of postcapillary venues. Proliferation centers are absent. The neoplastic lymphocytes have morphological and immunohistochemical characteristics of either CD4+ helper or CD8+ suppressor T cells [45,46]. Rare cases show a mixed immunophenotype with simultaneous CD4 and CDS positivity in the same cells.

Hairy cell leukemia

Hairy cells often show hair-like projections of their cytoplasm [47] on hematological smears and imprints. These projections are better recognized by electron microscopy. In the majority of cases the cells represent a peculiar, not fully defined B-cell variety [48,49]. Some authors relate hairy cells to B-monocytoid marginal zone cells of the lymph node cortex and to centrocyte-like cells of mucous-associated lymphoid tissue [50,51]. In very rare instances the hairy cells reveal characteristics of a T-cell [52] or even a monocytic [53,54] phenotype. Hairy cells are identified by their positivity to tartrate-resistant acid phosphatase and to acidify non-specific esterase [55]. In addition, monoclonal antibodies exist which recognize antigenic epitopes on hairy cells [56]. The usual immunophenotype of hairy cells corresponds to CD22, CD20 and CD29 positivity and CD5 and CD23 negativity. Hairy cells are also stained for HML-1 antibody, which was initially found to recognize intraepithelial T lymphocytes [57]. They also show positivity for CD11 c (KiM1 and KiM1 P in frozen and paraffin sections, respectively). Hairy cells are larger than typical lymphocytes with irregular ellipsoid or reniform nuclei. They stay apart from each other because of their relatively abundant cytoplasm which is hardly recognizable in H+E stained paraffin sections [47]. Lymph nodes are involved in advanced stages of the disease. Organs which are infiltrated early and whose biopsy contributes to the establishment of the diagnosis are bone marrow, spleen and liver. In bone marrow (Fig. 3) reticular fibers and even fibrosis are abundant [47] and responsible for the dry-tap reported by hematologists. In the spleen the infiltrates mainly occupy the cords of the expanded red pulp. The picture of the peripheral blood is not always clearly leukemia. Hairy cell leukemia in which the HTLV-2 virus has in some way been implicated [58] displays a rather indolent and long lasting course especially after appropriate therapy. The percentage of Ki-67-positive hairy cells is very low. However, second malignancies do occur in hairy cell leukemia patients

Lymphoplasmacytic/Lymphoplasmacytoid Lymphoma (LP-immunocytoma)

Histologically, LP-immunocytoma resembles B-CLL. In addition it shows various numbers of Ig-secreting cells of plasmacytic or lymphoplasmacytoid appearance [34]. The latter have moderate to abundant cytoplasm with rough endoplasmic reticulum-like plasma cells and a nucleus reminiscent of lymphocytes. PAS-positive intranuclear inclusions, representing Igs, are often found. Immunohistochemically  plasmacytic and plasmacytoid cells reveal cytoplasm monoclonal immunoglobulins [34,60, 61], which in descending frequency belongs to IgM, IgG or IgA. In 35% of the cases a paraproteinaemia is present. LP-immunocytoma is the tissue ground of the so-called macroglobulinaemia of Waldenstrom. In rare cases neoplastic cells produce only heavy or light chains of Igs, resulting in heavy (IgM, IgG) or light-chain disease, respectively. Two histological subtypes of LP-immunocytoma are described. The lymphoplasmacytoid subtype is morphologically and immunophenotypically more like B-CLL. It shows lymphoplasmacytoid cells and a phenotype of CD19+, CD20+, CD22+, CD5+ and CD23+ [62]. It not infrequently shows a leukemia picture and borderline cases to B-CLL exist [34].

The Lymphoplasmacytic subtype includes among the other neoplastic lymphocytes classic monoclonal plasma cells. The phenotype of neoplastic cells corresponds to CD19+, CD20+, CD22+, CDS- and CD23+/-. The presence of follicular dendritic cells, a feature reminiscent of MALTomas, characterizes more than half of the cases of the Lymphoplasmacytic subtype [63,64]. The prognosis of LP-immunocytoma is slightly more unfavorable than that of B-CLL. Accordingly, the percentages of Ki-67-positive lymphoid cells are slightly higher in LP-immunocytoma than in B-CLL. Paradoxical-ly it seems that leukemia cases have a better prognosis than aleukaemic cases [65]. The high-grade malignant lymphomas which may develop from LP-immunocytoma are usually immunoblastic.