MINIMAL RESIDUAL ACUTE LEUKEMIC DISEASE
Although cytogenetic and molecular techniques represent the gold standard for detecting minimal residual
disease, they are not generally available in most hospital pathology laboratories. Moreover, their high
cost and lengthy turnaround time represent serious drawbacks in a clinical setting. When convincing
evidence of the presence of residual blasts cannot be obtained by the morphologic examination of a properly
prepared bone marrow aspirate or when the marrow aspirate cannot be obtained because of myelofibrosis, or is
otherwise unavailable, a bone marrow biopsy specimen can be used to detect the presence of residual leukemic
disease. A small number of leukemic blasts is, however, difficult to identify by morphology.
Immunohistochemistry can be helpful in this setting by facilitating the identification of leukemic blasts in
tissue sections. The antibodies which we find most useful are the ones restricted to blasts and immature
cells (e.g. CD34, TdT, CD99).
CD34 staining has been shown to be of value in predicting the presence of residual disease and impending
relapse in patients with acute leukemia in morphologic remission. In our experience the presence of
residual blasts is often easier to document in ALL than in AML. In the former group of disorders CD34 is
more frequently expressed than in AML, in which blasts are CD34 positive in approximately 40% of cases . TdT
is also much less commonly expressed in AML than in ALL.
Residual ALL blasts in cases of precursor B-cell ALL can also be detected by their positivity with TdT,
CD99, and CD79a. In CD34 negative AML, blasts can often be detected by a careful morphologic analysis of
hematoxylin-eosin or Giemsa stained sections and their comparison with corresponding sections stained by
myeloperoxidase, CD68, or any other marker present on the leukemic cells at the outset of the disease.
References
- Rimsza LM, Viswanatha DS, Winter SS, Leith CP, Frost JD, Foucar K. The presence of CD34+ cell clusters
predicts impending relapse in children with acute lymphoblastic leukemia receiving maintenance chemotherapy.
Am J Clin Pathol 1998;110:313-20.
- Rimsza et al: Benign hematogone-rich lymphoid proliferations can be distinguished from B-lineage acute
lymphoblastic leukemia by integration of morphology, immunophenotype, adhesion molecule expression, and
architectural features. Am J Clin Pathol. 2000;114:66-75.
- Worapongpaiboon S, Shapira G, Neiman R, Heerema N, John K, Orazi A.: CD34 immunostaining, a potentially
useful technique to assess minimal residual disease in CD34(+) acute leukemia. United States and Canadian
Academy of Pathology, 86th Annual Meeting, Orlando, Florida, March 1-7, 1997. Lab Invest 1997;76:136A.
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