Concordance among hematopathologists in classifying blasts plus promonocytes: A bone marrow pathology group study

Area of Science:

• Hematology
• Oncology
• Cellular Morphology

Background:

• Accurate classification of myelomonocytic neoplasms is crucial for patient management and treatment.
• Distinguishing blasts, promonocytes, and monocytes, including normal versus abnormal monocytes, presents diagnostic challenges.
• The World Health Organization (WHO) classification relies on precise enumeration of these cell types.

Purpose of the Study:

• To evaluate inter-observer agreement among experienced hematopathologists in classifying blasts, promonocytes, and monocytes.
• To assess the consistency of applying WHO criteria for myelomonocytic neoplasms.
• To determine if combining blasts and promonocytes into a single category improves classification concordance.

Main Methods:

• 11 hematopathologists reviewed slides from 20 patients (12 with chronic myelomonocytic leukemia [CMML], 8 with acute myeloid leukemia [AML]).
• Included peripheral blood (PB) and bone marrow (BM) aspirate smears, with limited nonspecific esterase (NSE) stains.
• Statistical analysis used Fleiss' kappa for multiple raters and Spearman's rank correlation.

Main Results:

• High concordance was observed for classifying patients based on the sum of blasts and promonocytes in both BM (kappa=0.744) and PB (kappa=0.949).
• Hematopathologists achieved a good concordance rate (74%) in distinguishing CMML from AML.
• Distinguishing abnormal from normal monocytes in PB showed poor concordance (P < .0001).

Conclusions:

• The criteria for defining blasts equivalents (blasts plus promonocytes) can be applied consistently.
• Combining blasts and promonocytes into a single category is supported by the findings.
• Further refinement is needed for the consistent identification of abnormal monocytes.