Hematopathology: Practice Question

A 60 year old patient is preliminarily diagnosed with the blastoid variant of mantle cell lymphoma. Further studies result in a diagnosis of lymphoblastic lymphoma. Which of the following would support the diagnosis of lymphoblastic lymphoma?
  1. TdT expression
  2. CCND1 mutation
  3. CD19, CD20, CD22, CD79a positivity
  4. CD5 expression
  5. Dimorphic leukemic lymphocytes
Show Answer and Explanations

TdT expression — Correct answer

Correct. Lymphoblastic lymphoma, is the lymphoma version of acute lymphoblastic leukemia (ALL). It is positive for TdT, and negative for BCL-1 and CD5, unlike the blastoid variant of mantle cell lymphoma. Both of these entities can be leukemic.

CCND1 mutation

Incorrect. The t(11;14) places IgH upstream from CCND1, which leads to increased cyclin D1 / BCL-1 expression in mantle cell lymphoma.

CD19, CD20, CD22, CD79a positivity

Incorrect. Both the blastoid variant of mantle cell lymphoma and lymphoblastic lymphoma express pan B cell markers.

CD5 expression

Incorrect. Mantle cell lymphoma is positive for CD5 and BCL-1, as well as FMC7. Lymphoblastic lymphoma is positive for TdT.

Dimorphic leukemic lymphocytes

Incorrect. If leukemic, the blastoid variant of mantle cell lymphoma usually shows a dimorphic population of lymphocytes with mature and blast forms.

Summary

Summary: For distinguishing the blastoid variant of mantle cell lymphoma and lymphoblastic lymphoma: blastoid MCL is CD5 and BCL-1 positive, lymphoblastic lymphoma is TdT positive.
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