Diagnostic and prognostic utility of flow cytometric DNA measurements in follicular thyroid tumors

Abstract

Distinguishing cellular follicular adenomas (FA) from minimally invasive follicular carcinomas (FC) continues to plague even experienced thyroid pathologists. DNA ploidy analysis has been promoted as a means of making this differentiation; however, the finding of DNA aneuploidy in FA has caused concern that they may demonstrate potential for malignant behavior or should even be reclassified as low-grade noninvasive cancers. In histologically-proven FC, nuclear DNA content has been claimed to have predictive power equivalent to that of all other prognostic factors combined. The aims of the present study, therefore, were to define the DNA ploidy characteristics of FA and FC, to assess the diagnostic potential of cell-cycle parameters, and, in FC, to investigate the prognostic role of such measurements. We measured DNA content of 124 tumors (60 FA, 64 FC). DNA pattern was normal (diploid) in 75% of FA and 45% of FC, tetraploid/polyploid (T/P) in 13% of FA and 25% of FC, and aneuploid in 12% of FA and 30% of FC. FC was histologically verified in 39% of DNA normal, 67% of T/P, and 73% of aneuploid tumors. DNA index, S-phase, G2M, and S-phase plus G2M were analyzed and were not helpful in differentiating between FA and FC. No patient with FA developed tumor recurrence. In FC (excluding the Hürthle cell variant), no significant differences were found among the 3 DNA ploidy groups with respect to either cancer death or tumor recurrence; however, combining the Hürthle cell variant of follicular carcinomas with pure follicular carcinomas, the presence of distant metastases, DNA aneuploidy, and patient age were the only independently significant prognostic variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent Developments in the Molecular Biology of the Thyroid

“…Thus, less than 10% of papillary carcinoma are aneuploid [178,179], while 20-30% of follicular adenomas and approximately 50% of follicular carcinomas have aneuploid cell population [180][181][182][183]. The frequency of aneuploidy tends to increase from follicular adenomas to minimally to widely invasive follicular carcinomas, although a significant overlap between these groups exists, which precludes the usage of the test for diagnostic purposes.…”

Effect of sonication on paraffin‐embedded tissue preparation for DNA flow cytometry

“…The use of a cup horn has the advantage that the specimens can be sonicated in small groups of samples and the samples are in closed test tubes and need not come into direct contact with the transducer. A preliminary study using different periods of time (2,4,5,6,7,8,10, and 15 min) indicated 4 min was optimal for most tissue types when using the equipment described above.…”

“…The DNA ploidy classification of specimens was also compared pre-and post-sonication. Four of 96 breast cancer samples changed classification; all were specimens in which the histogram became cleaner and a small DNA aneuploid peak became apparent after sonication.Key terms: DNA aneuploidy, cell clumping, sample aggregation, propidium iodide, breast cancer S-phase measurements Since the description of a nuclear extraction method for paraffin-embedded archival tumor samples (61, a number of reports (1,4,5,8,11) have demonstrated the value of DNA content analysis in predicting clinical outcome. The use of fluorescent DNA dyes and flow cytometry allows the identification of abnormal cell clones that have grossly abnormal DNA content (DNA aneuploid).…”

“…In many tumor systems, studies have shown that DNA aneuploid tumor clones predict shortened survival. In some of these tumor types, DNA aneuploidy is an independent prognostic factor (4,5,11). In thyroid, kidney, and prostate tumors, the presence of a high percent of G,/M cells (DNA tetraploid) has the same prognostic significance as DNA aneuploid (5,ll).…”

Follicular Neoplasms of the Thyroid

“…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, 9-11,18 morphometric criteria like nuclear diameter, 1,2,12 and number and margination of nucleoli 14-17 and flow cytometry, 3,5,6 either singly or in combination. The sensi-…”