Page 381 - Textbook of Pathology, 6th Edition

of infection. This is achieved by bowel sterilisation and by However, while HD can be identified by the patho- 365
topical antiseptics. If these fail to achieve the desired results, gnomonic presence of Reed-Sternberg cells, there have been
systemic antibiotics and leucocyte concentrates are controversies and confusion in classification of other
considered for therapy. lymphoid cancers (i.e. NHL and lymphoid leukaemias). In
order to resolve the issue, over the years several classification
III.CYTOTOXIC DRUG THERAPY. The aims of cytotoxic schemes have emerged for lymphoid cancers due to
therapy are firstly to induce remission, secondly to continue following two main reasons:
therapy to reduce the hidden leukaemic cell population by
repeated courses of therapy. Most commonly, cyclic 1. Biologic course of lymphoma-leukaemia. While some
combinations of 2, 3 and 4 drugs are given with treatment- of the lymphoid malignancies initially present as leukaemias
free intervals to allow the bone marrow to recover. (i.e. in the blood and bone marrow), many others present as
The most effective treatment of AML is a combination of solid masses in the lymphoid tissues or in various other
3 drugs: cytosine arabinoside, anthracyclines (daunorubicin, tissues, especilly in the spleen, liver, bone marrow and other
adriamycin) and 6-thioguanine. Another addition is tissues. Still others may have initial presentation as either
amsacrine (m-AMSA) administered with cytosine leukaemia or lymphomas. In fact, the line of demarcation
arabinoside, with or without 6-thioguanine. Following for lymphoid malignancies is so blurred that during the
remission-induction therapy, various drug combinations are biologic course of the disease, lymphoid leukaemia or CHAPTER 14
given intermittently for maintenance. However, lymphoma may spill over and transform to the other.
promyelocytic leukaemia (M3) is treated with tretinoin orally 2. Technological advances. In recent times, modern
that reduces the leukaemic cells bearing t(15;17)(q22;q21) diagnostic tools have become available to pathologists and
but devlopment of DIC due to liberation of granules of dying haematologists which go much beyond making the diagnosis
cells is a problem.
of lymphomas and leukaemias on clinical grounds combined
IV.BONE MARROW TRANSPLANTATION. Bone with morphology and cytochemical stains alone. This
marrow (or stem cell) transplantation from suitable allogenic includes methods for immunophenotyping, cytogenetics and
or autologous donor (HLA and mixed lymphocytes culture- molecular markers for the stage of differentiation of the cell
matched) is increasingly being used for treating young adults of origin rather than location of the cell alone.
with AML in first remission. The basic principle of marrow These aspects form the basis of current concept for WHO
transplantation is to reconstitute the patient’s haematopoietic classification of malignancies of lymphoid cells of blood and
system after total body irradiation and intensive lymphoreticular tissues as ‘lymphoid neoplasms’ as a unified
chemotherapy have been given so as to kill the remaining group. However, it needs to be appreciated that in several
leukaemic cells. Bone marrow transplantation has resulted centres in developing countries of the world, limited
in cure in about half the cases. laboratory facilities are available. Thus, judiciously speaking,
Remission rate with AML is lower (50-70%) than in ALL, some of the older classification schemes for lymphoid
often takes longer to achieve remission, and disease-free malignancies need to be retained, while others can be Disorders of Leucocytes and Lymphoreticular Tissues
intervals are shorter. AML is most malignant of all dumped as historical. In view of this, a balanced
leukaemias; median survival with treatment is 12-18 months. approach of middle path of retaining old and including new
classification schemes of lymphoid malignancies is
proposed to be followed for discussion below:
LYMPHOID NEOPLASMS
I. HISTORICAL CLASSIFICATIONS. These classifica-
Lymphoid cells constitute the immune system of the body. tions can be traced as under:
These cells circulate in the blood and also lie in the lymphoid
tissues and undergo differentiation and maturation in these Morphologic classification. Rappaport classification (1966)
organs. The haematopoietic stem cells which form myeloid proposed a clinically relevant morphologic classification
and lymphoid series, undergo further differentiation of based on two main features: low-power microscopy of the
lymphoid cells into B cells (including formation of plasma overall pattern of the lymph node architecture, and high-power
cells), T cells and NK cells. Lymphoid malignancies can be microscopy revealing the cytology of the neoplastic cells.
formed by malignant transformation of each of these cell Based on these two features, Rappaport divided NHL into
lines. These lymphoid malignancies can range from indolent two major subtypes:
to highly aggressive human cancers. 1. Nodular or follicular lymphomas which retain some of the
Conventionally, malignancies of lymphoid cells in blood features of normal lymph node in that the neoplastic cells
have been termed as lymphatic leukaemias and those of form lymphoid ‘nodules’ rather than lymphoid follicles with
lymphoid tissues as lymphomas. Just like myeloid germinal centres.
leukaemias discussed earlier, lymphoid leukaemias have 2. Diffuse lymphomas, on the other hand, are characterised
been classified on the basis of survival and biologic course, by effacement of the normal lymph node architecture and
into chronic and acute (CLL and ALL). Similarly, two there may be infiltration of neoplastic cells outside the
clinicopathologically distinct groups of lymphomas are capsule of the involved lymph node.
distinguished: Hodgkin’s lymphoma or Hodgkin’s disease (HD) NHL was further classified according to the degree of
and non-Hodgkin’s lymphomas (NHL). differentiation of neoplastic cells into: well-differentiated,