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A 32-year-old man is diagnosed with non-Hodgkin lymphoma. Even without knowing the
specific diagnosis, it can safely be said that this patient's lymphoma is characterized by
A. B-lymphocytic origin
B. histiocytic origin
C. lymph node localization
D. monoclonal origin
E. T-lymphocytic origin
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The correct answer is D. All lymphomas are monoclonal, derived from neoplastic expansion of
a single transformed cell clone. A corollary of the monoclonal origin of lymphoid neoplasms is
that the daughter cells derived from a single malignant precursor share the same configuration of
antigen receptor genes and produce identical antigen receptor proteins (either immunoglobulins
or T-cell receptors). Gene rearrangement studies, therefore, can be used for diagnostic purposes
to determine whether a lymphoid population is monoclonal (ie, neoplastic) or polyclonal (ie,
reactive)
Most, but not all, non-Hodgkin lymphomas are of B lymphocytic origin (choice A).
Approximately 80% of non-Hodgkin lymphomas are derived from B lymphocytes; the remaining
20% are of histiocytic (choice B) or T lymphocytic (choice E) origin. An example of T cell
leukemia/lymphoma is mycosis fungoides/Sézary syndrome. Langerhans cell histiocytosis
belongs to the small group of histiocytic neoplasms and is a spectrum of neoplastic conditions
due to proliferation of Langerhans cells.
Lymph node localization (choice C) is variably present in non-Hodgkin lymphomas. Two thirds
of these lymphomas come to clinical attention with nontender nodal enlargement involving one
or more lymph nodes. The remaining one third of cases present with extranodal involvement of
skin, brain, and gastrointestinal tract, for example. In contrast, virtually all cases of Hodgkin
lymphoma present with lymph node enlargement.
