Background

The Mitosis-Karyorrhexis Index (MKI) score is important in neuroblastoma evaluation and in the application of the International Neuroblastoma Pathology Classification (INPC). Currently, it is not standardized for smears. Hence, the aim of this study was to devise and validate methods for MKI evaluation in fine-needle aspiration biopsy (FNAB) of neuroblastoma.

Methods

A total of 50 cases of neuroblastoma diagnosed by FNAB from January 2017 to December 2019 were retrieved, and detailed cytomorphological evaluations were performed. The MKI was evaluated, and the eyeball visual assessment score (EVAS) was compared with the digital image visual analysis score (DIVAS) on cytology smears and corresponding histology sections of cell blocks. The interobserver reproducibility and concordance were calculated. INPC subtyping into favorable and unfavorable groups was performed by the collation of age, MKI, and cytomorphology and was correlated to clinical outcomes.

Results

Neuroblastoma was categorized as undifferentiated (22 of 50) or poorly differentiated (28 of 50) on cytomorphology. The overall concordance for the MKI by 3 observers was 86% (κ = 0.85), and this increased to 98% in the high MKI category. MKI evaluations on smears showed 96% concordance with cell block histology, and the EVAS was concordant with the DIVAS in 86% of the cases. Overall, the MKI was high in 39 cases, intermediate in 4 cases, and low in 7 cases. The INPC category was unfavorable in 90% (n = 45) and favorable in 10% (n = 5) and had significant correlations with outcomes (P = .029).

Conclusions

An MKI assessment on smears by digital image visual analysis is accurate, reproducible, and objective and should be incorporated into the routine reporting of neuroblastoma FNAB for diagnostic schemas as per the INPC.