45-year-old male exhibited painless swelling of inguinal lymph nodes. A lymph node was excised.
- The entire lymph node is permeated by ill-defined, closely packed follicles lacking a mantle zone. Some follicles are arranged back-to-back. Polarisation of follicles and starry-sky pattern are not observed.
- Two cell types can be distinguished. Small to medium-sized cells with angulated nuclei, inconspicuous nucleoli and scant cytoplasm (centrocytes) are predominant. Large transformed cells with indented nuclei, vesicular chromatin containing one to three nucleoli (centroblasts) are scattered in between centrocytes.
- The malignant cells infiltrate the capsule of the lymph node and the surrounding adipose tissue.
Follicular lymphomas belong to the group of mature B-cell lymphomas. Together with diffuse large B-cell lymphomas they account for 50% of all Non-Hodgkin lymphomas. Follicular lymphomas are graded based on the number of centroblasts. Grade 1 and 2 disease is indolent but usually not curable (low grade lymphoma). In contrast, grade 3 disease is more aggressive and potentially curable (high grade lymphoma).