Well Differentiated Follicular Neoplasms of the Thyroid: Reproducibility and Validity of A‘Decision Tree’Classification Based On Nucleolar and Karyometric Features

Abstract

This study was conducted on fine-needle aspirates of well differentiated follicular neoplasms of the thyroid. A 'decision tree' classification based on the percentage of nucleolated nuclei, percentage of nuclei with two or more nucleoli and mean major nuclear diameter was adopted. We observed that the reproducibility and the validity of the follicular adenoma vs follicular carcinoma discrimination are greater than in the subjective evaluation. Moreover, similar classification results were obtained when measurements were performed either with a fully automated image analysis system or with semiautomatic or manual instrumentation. As for reproducibility of the inter-instrument comparisons, the k statistic values ranged from 0.85 to 1.00 (mean value 0.90, that is, an 'almost perfect' degree of agreement); in the subjective evaluations, the inter-observer comparisons showed values ranging from 0.20 to 0.56 (mean value 0.37, that is, 'fair'). In the decision tree classification, feature value thresholds were selected in order to have specificity of 100% and the predictive value of a positive result (carcinoma) of 100%; accuracy was 87% (range 86-89%), sensitivity 74% (71-79%), the predictive value of a negative result (adenoma) 79% (78-82%). In the subjective evaluation the values were as follows: accuracy 67% (64-71%), sensitivity 57% (50-64%), specificity 77% (71-79%), predictive value of a negative result (adenoma) 64% (61-69%), predictive value of a positive result (carcinoma) 71% (67-75%). The conclusion is that, by using a routine microscope equipped with a micrometer, the preoperative diagnosis of follicular carcinoma from smears can be formulated with a high degree of certainty.

Thyroid Cancer: 1999 Update and Evaluation of Solitary Thyroid Nodules

“…These histological findings require more tissue than can be obtained by FNA biopsy; a cytopathologist cannot differentiate between follicular or Hurthle cell adenoma and carcinoma based solely on a cytological examination. 18 -20 Use of additional cytological parameters, such as the cellular pattern, [21][22][23] nuclear diameter, 24 number and margination of nucleoli, 25,26 and DNA pattern as measured by flow cytometry, [27][28][29] has met with limited success in differentiating follicular or Hurthle cell carcinomas from adenomas. A repeat FNA biopsy may eliminate the misdiagnosis of benign lesions, although it cannot differentiate between benign and malignant follicular lesions.…”

Follicular Neoplasms of the Thyroid

“…Thus, only two cases of carcinoma were falsely called benign. Though our decision tree classification has specificity and sensitivity values lower than Montironi's, 16 we think that we have developed a classification that is simpler (though not with the high sensitivity and specificity of Montironi's classification). It is simpler mainly because nucleolar counts are extremely cumbersome and, as we saw in our study, unhelpful, also.…”

“…Montironi and coworkers, in various studies, [14][15][16][17] had shown the ability of nucleolar counts to differentiate follicular adenomas from follicular carcinomas. In our study all the nucleolar parameters studied showed an overlap (including nuclear margination).…”

“…In our study all the nucleolar parameters studied showed an overlap (including nuclear margination). Montironi et al 16 even developed a decision tree classification to segregate adenomas and carcinomas based on nucleolar counts. We, to the best of our knowledge, have used the same methodology as Montironi's.…”

“…In spite of the profusion of work available, only marginal success has been achieved in separating them cytologically. Parameters used for this purpose include morphologic features, such as cellular patterns, [9][10][11]18 morphometric criteria like nuclear diameter, 1,2,12 and number and margination of nucleoli [14][15][16][17] and flow cytometry, 3,5,6 either singly or in combination. The sensi-tivity of these results has varied from 40% 19 to 75%.…”