Scoring criteria for the evaluation of micronuclei in oral exfoliated cells.

Dear Editor,

With reference to the article titled, “An in vivo cytogenetic analysis of human oral squamous cell carcinoma”[1] published in your esteemed journal, I would like to bring into notice a few important points regarding the scoring criteria used for the evaluation of micronuclei.

The criteria used for the evaluation of micronuclei in the above-mentioned study are as follows:[2]

The diameter of micronucleus (MN) in human lymphocytes usually varies between 1/16 and 1/3 of the mean diameter of the main nuclei which corresponds to 1/256 and 1/9 of the area of one of the main nuclei in a BN cell, respectively

MN is round or oval

MN is nonrefractile and it can, therefore, be readily distinguished from artifacts such as staining particles

MN is not linked or connected to the main nuclei

MN may touch but will not overlap the main nuclei, and the micronuclear boundary should be distinguishable from the nuclear boundary

MN usually has the same staining intensity as the main nuclei but occasionally staining may be more intense.

First of all, the above-said criteria are for the evaluation of micronuclei in lymphocytes and not exfoliated oral cells (as in the given study, micronuclei were evaluated in exfoliated oral cells). Second, the micronuclei showed in the images provided do not comply by the criteria used (micronuclei shown in the image are refractile and overlapping). The most accepted criterion[3] for the evaluation of micronuclei in oral exfoliated cells is as follows:

Rounded smooth perimeter suggestive of a membrane

Less than one-third of the diameter of the associated nucleus, but large enough to discern the shape and color

Staining intensity similar to that of the nucleus

Texture similar to that of the nucleus

Same focal plane as the nucleus

Absence of overlap with, or bridge to, the nucleus.

Since there is a considerable similarity between the two criteria, using the former criterion is technically not wrong, provided it is fulfilled completely.

To conclude, I request the authors to go through their images again and make sure they are compatible with the criterion used. The purpose of this letter is not to highlight an error rather to focus on the appropriate criterion to be used for future studies. Such parameters play a vital role in establishing the validity of the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.