Malignant Hematolymphoid Plasmacytic Effusions: A Cytopathologic Study of Six Cases

Area of Science:

• Cytopathology
• Hematopathology
• Oncology

Background:

• Hematolymphoid plasmacytic effusions (HPEs) are understudied compared to myelomatous effusions.
• Accurate diagnosis of HPEs is challenging due to potential misinterpretation as reactive plasmacytosis or other malignancies.

Purpose of the Study:

• To investigate the prevalence, cytologic patterns, diagnostic pitfalls, and clinical associations of HPEs.
• To highlight the utility of cellblock immunocytochemistry in diagnosing HPEs.

Main Methods:

• Retrospective review of serous effusion fluids over 15 years.
• Classification of HPEs based on >10% plasmacytoid and plasma cells.
• Analysis of clinical, laboratory, and follow-up data.
• Confirmation of diagnosis using light chain immunomarkers in cellblock sections.

Main Results:

• HPEs constituted 0.2% of serous effusions, identified in six elderly patients (average age 73).
• Identified three cytomorphologic patterns: pure plasmacytic, lymphoplasmacytic, and mixed infiltrates.
• Diagnoses included multiple myeloma (4 patients) and B-cell lymphomas (2 patients).
• Equal distribution of kappa and lambda light chain restriction was observed.

Conclusions:

• HPEs are uncommon malignant effusions associated with multiple myeloma and low-grade B-cell lymphomas in elderly individuals.
• Distinguishing high-grade myeloma cells and mature plasma cells from reactive conditions requires careful cytologic evaluation and immunocytochemistry.
• Cellblock immunocytochemistry is essential for confirming HPE diagnoses, especially when fluid flow cytometry is unavailable.