An Overview of Discordant Lymphoma

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A person is said to have discordant bone marrow involvement or “discordant lymphoma” when two different types of lymphoma are identified in the same person at two separate sites in the body.

In non-Hodgkin’s lymphoma, or NHL, discordant bone marrow involvement typically happens when an aggressive lymphoma is found in a lymph node biopsy but an indolent or slow-growing lymphoma is found in the bone marrow biopsy.

The impact, if any, of concordance and discordance of bone marrow involvement in lymphoma seems to depend on the types of lymphoma found as well as some additional context about the course of the disease. Generally, drawing firm conclusions about prognosis based upon concordant or discordant bone marrow involvement is challenging because, in many cases, published data that doctors rely upon are very limited.

Dividing lymphoma cancer cells

Bone Marrow Involvement

Most indolent or slow-growing B-cell lymphomas have bone marrow involvement at the time of diagnosis. With respect to diffuse large B-cell lymphoma (DLBCL), which is an aggressive type of non-Hodgkin's lymphoma, most studies report that only about 10 to 15% of cases have bone marrow involvement when diagnosed. Nevertheless, testing the bone marrow is important.

Concordance and Discordance

When bone marrow involvement occurs in non-Hodgkin's lymphoma, it is usually the case that the cancer cells in the bone marrow are similar to the cancer cells found at other sites, such as in the lymph nodes and this is known as concordance.

Discordance refers to those lymphoma cases where the histology, or the characteristics and appearance of the cancerous cells, differs in important ways between the bone marrow and the other sites of involvement.

Discordant is different from composite, which refers to two or more distinct areas of lymphoma cells in the same lymph node sample.

Discordance is also different from transformation which refers to a lymphoma that starts out slow-growing or indolent but then undergoes transformation into aggressive lymphoma (usually DLBCL) during the course of the disease. Richter transformation is an example of transformation that involves chronic lymphocytic leukemia that transforms into DLBCL or Hodgkin lymphoma.

Diagnosis, Treatment, and Outcome

There is not a lot of consensus on how frequently discordant lymphomas are diagnosed, how they behave clinically, or how best to treat them, unfortunately. Data are mostly derived from single cases that have been reported in the scientific literature and small studies that look back to try to figure out patterns and associations.

Concordant bone marrow involvement has been linked historically to worse survival outcomes in patients with nodal follicular lymphoma. The finding causes an upgrading to an Ann Arbor stage of IV and thus a higher score on an index used to gauge prognosis, the FLIPI score.

Discordant bone marrow involvement seems to be relatively infrequent among the slow-growing lymphomas; concordant involvement has been estimated to occur in 40 to 70 percent of patients with follicular lymphoma. Discordant bone marrow involvement in marginal zone lymphoma appears to be similarly infrequent.

A Word From Verywell

According to the authors of the 2016 article, more studies with larger numbers are needed to be able to better tell what concordance and discordance mean for many patients with lymphoma.

  • Concordant bone marrow involvement with DLBCL seems to indicate a worse outcome and worse overall survival compared with cases without bone marrow involvement.
  • Discordant bone marrow involvement with an indolent or slow-growing B-cell lymphoma in newly diagnosed DLBCL does not appear to impact negatively on prognosis.

And, although FDG-PET is a helpful tool in the diagnosis of concordant bone marrow involvement in DLBCL, it is probably much less sensitive in detecting discordant bone marrow involvement.

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