RNA test identifies large B-cell lymphoma subtypes

Answers from the Lab

Precise diagnosis is key to choosing the optimal chemotherapy for large B-cell lymphoma. In this test-specific episode of the "Answers From the Lab" podcast, Lisa Rimsza, M.D., explains how Mayo Clinic Laboratories' unique PM3CX test accurately distinguishes among multiple subtypes of this cancer.

"PM3CX is a qualitative RNA test," Dr. Rimsza says. "It first tells you if the patient has primary mediastinal large B-cell lymphoma or diffuse large B-cell lymphoma (DLBCL). The test can also identify subtypes of DLBCL."

Using gene expression profiling, the test avoids challenges associated with immunostaining and biopsies of delicate tissue. "The molecular test is very accurate and reproducible," Dr. Rimsza says. "There is no other molecular test like this, for this disease."

Test results can directly impact treatment decisions. "Clinicians need to know whether a patient has the more typical DLBCL — which gets one type of chemotherapy — or in fact has the primary mediastinal large B-cell type, which gets a different chemotherapy," Dr. Rimsza says.

Listen to learn more about Mayo Clinic Laboratories' PM3CX test.

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Useful information

Only indicated for formalin-fixed paraffin-embedded specimens from patients diagnosed with large B-cell lymphoma.

Specimen requirements

Submit only 1 of the following specimens:


  • Specimen Type: Tissue slides
  • Slides: 1 stained and 7 unstained
  • Collection Instructions: Submit 1 slide stained with hematoxylin and eosin and 7 consecutive, unstained, 5-micron thick sections placed on positively charged slides.
  • Additional Information: Paraffin embedded specimens can be from any anatomic location (skin, soft tissue, lymph node, etc).


  • Specimen Type: Tissue block
  • Collection Instructions: Submit a formalin-fixed, paraffin-embedded tumor tissue block.

Specimen minimum volume

  • Minimum 60% tumor with or without macrodissection.
  • Minimum required unstained tissue section input: 0.12 mm(3)

Performance information

  • Analytic time: 7 to 12 days
  • Day(s) and time(s) performed: Monday through Friday

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Barbara J. Toman

Barbara J. Toman is a Senior Communications Specialist at Mayo Clinic Laboratories. She is also the science writer for Mayo’s Neurosciences Update newsletter, which helps referring physicians to stay informed about Mayo’s treatment and research. Barbara has worked at Mayo Clinic since 2007. She enjoys international travel and cooking.