Follicular Lymhoma with Transformation into Diffuse Large B-cell Lymphoma & Transdifferentiation into a Histiocytic/ Dendritic Neoplasm

Lessons From the Friday Unknows

Histologic examination reveals follicular lymphoma, grade 1–2 and grade 3A, with transformation into diffuse large B-cell lymphoma and transdifferentiation into histiocytic/dendritic cell neoplasm.

Areas with follicular lymphoma, grade 1:

Areas with diffuse large B-cell lymphoma:

Areas with histiocytic/ dendritic cell tumor:

Flow cytometric analysis revealed aberrant, kappa restricted B-cells positive for CD10 (dim), CD20 and FMC-7.

The follicular lymphoma and diffuse large B-cell lymphoma components are positive for CD20, CD79a, Pax-5, CD10, Bcl-2 and Bcl-6, with non-immunoreactivity for CD30, CD3 and CD5.

Cells within the separate histiocytic lesion are reported to have been positive for CD4, CD68, CD163, S-100 and lysozyme and negative for CD20, Pax-5, CD79a, CD1a, ALK-1, CD3, CD5, CD30 and CD21.

Link to digital slides: https://bit.ly/3kHiFSi | Slides labeled case 5