Fine-needle aspiration biopsy of lymphoproliferative disorders--interpretations based on morphologic criteria alone: results from the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytopathology.

Context: Diagnosis of lymphoproliferative disorders is one of the most challenging tasks faced by the cytologist. The initial cytomorphologic evaluation of lymphoproliferative lesions directs the choice of ancillary studies that ultimately lead to a diagnosis based on the World Health Organization classification system using a composite of clinical, morphologic, immunophenotypic, and molecular features.

Objective: To evaluate the ability of participating laboratories in the College of American Pathologists Interlaboratory Comparison Program in Non-Gynecologic Cytopathology to appropriately categorize lymphoproliferative lesions based solely on cytomorphologic criteria.

Design: Laboratory responses for lymph node aspirates were examined. All responses were based on review of glass slides without ancillary immunologic or molecular data available. The benchmarking data provided for each specific diagnosis were analyzed, with a focus on the performance for evaluation of lymphoproliferative lesions.

Results: Based on morphology alone, responses for lymph node aspirates in the Non-Gynecologic Cytopathology program were correct to the exact reference diagnosis for 87.1% of Hodgkin lymphoma. Non-Hodgkin lymphoma was identified in 69.5% of the large cell non-Hodgkin lymphoma cases, of which 66.8% were correctly classified as large cell type. Non-Hodgkin lymphoma was identified in 68.1% of non-Hodgkin lymphoma, other than large cell cases, and of these, 94.7% were identified as other than large cell type.

Conclusions: The spectrum of specific responses was consistent for lymphoproliferative lesions, with a reasonable differential diagnosis based on cytomorphology alone, which, in practice, facilitates the appropriate choice of immunophenotypic markers and other ancillary studies.