Differential Diagnosis
- Single most likely diagnosis
- Follicular Lymphoma: The presence of CD10 diffuse positivity, BCL-6 focal weak positivity, and CD20 positivity are characteristic of follicular lymphoma. The Ki-67 index of 15% to 20% is also within the range expected for this diagnosis.
- Other Likely diagnoses
- Burkitt Lymphoma: Although less likely due to the absence of a high Ki-67 index (typically >95% in Burkitt lymphoma) and the lack of strong MYC expression, the CD10 diffuse positivity and BCL-2 positivity could still suggest this diagnosis, especially if morphological features are considered.
- Diffuse Large B-Cell Lymphoma (DLBCL): The presence of CD10 and BCL-6 positivity, along with a moderate Ki-67 index, could also suggest DLBCL. However, the focal weak MYC expression and lack of strong cyclin D1 staining make it less typical.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Double Hit Lymphoma: Although MYC expression is only focal and weak, and BCL-2 is positive, the combination of these markers with CD10 positivity necessitates consideration of a double hit lymphoma, which has a poor prognosis and requires aggressive treatment.
- Mantle Cell Lymphoma: Despite the lack of cyclin D1 positivity, which is a hallmark of mantle cell lymphoma, the presence of CD5 on reactive T cells and the overall immunophenotypic profile should prompt consideration of this diagnosis, especially if the clinical context or morphology suggests it.
- Rare diagnoses
- High-Grade B-Cell Lymphoma with MYC and BCL-2 and/or BCL-6 rearrangements (Double-Expressor Lymphoma): This is considered due to the presence of MYC, albeit focal, and BCL-2 positivity, but it's less likely given the lack of strong MYC expression and specific genetic studies would be needed to confirm.
- In Situ Follicular Neoplasia: Although rare, the presence of CD10 and BCL-6 positivity within a follicular pattern could suggest this diagnosis, but it would require correlation with morphology and clinical context.