Histology

Macroscopy: Six pale core needle biopsies, the largest up to 20 mm.

Microscopy: All core needle biopsies are entirely replaced by solid sheets and cords of small-to-medium sized atypical lymphoid cells infiltrating into the adipose tissue. There is no normal renal tissue identified in these biopsies. The cells diffusely express [LCA] while cytokeratin AE1/3 is entirely negative.

These pathologic findings are compatible with a non-Hodgkin's lymphoma. The imaging findings corroborate this diagnosis as well.