Plasmacytic differentiation in follicular center cell (FCC) lymphomas

Area of Science:

• Hematopathology
• Oncology
• Immunology

Background:

• Follicular centers are key sites for plasma cell precursor production.
• Plasmacytic differentiation is typically infrequent in follicular center cell (FCC) lymphomas.
• A differentiation block in large noncleaved FCCs is hypothesized to limit plasmacytic differentiation.

Purpose of the Study:

• To determine the frequency of plasmacytic differentiation in FCC lymphomas.
• To investigate the diagnostic implications of plasma cell presence in FCC lymphomas.

Main Methods:

• Retrospective review of 198 consecutive FCC lymphomas with a follicular pattern.
• Immunoperoxidase studies on paraffin-embedded sections for cytoplasmic immunoglobulin.
• Surface typing studies for immunoglobulin expression.
• Serum paraprotein analysis.

Main Results:

• 17 out of 198 (9%) FCC lymphomas exhibited a significant number of plasma cells.
• Ten cases showed polytypic plasma cell marking, while seven had monotypic plasma cell populations.
• In seven cases with monotypic plasma cells, isotypic identity with FCC populations was confirmed via immunoperoxidase and/or surface typing.
• Three patients presented with serum paraproteins identical to the plasma cell immunoglobulins.

Conclusions:

• A small subset of FCC lymphomas can present with a substantial plasma cell component, posing potential diagnostic challenges.
• In some FCC lymphomas, plasma cells represent a differentiated component of the neoplastic process.
• These findings highlight the importance of careful immunophenotypic analysis in diagnosing FCC lymphomas with plasmacytic features.