Poorly differentiated thyroid carcinoma (PDTC) is an uncommon and aggressive malignancy. Despite the significant clinical implications of a diagnosis of PDTC, its cytomorphologic features have not been well defined. Statistical analysis was applied to a series of 40 PDTCs to identify a specific set of cytomorphologic features that characterized these tumors on fine-needle aspiration biopsy (FNAB).
In total, 40 thyroid FNABs that were highly diagnosed histologically as PDTC (19 insular carcinomas and 21 noninsular carcinomas) comprised the study group. A control group of 40 well differentiated thyroid neoplasms were selected for comparison. All FNABs were reviewed and scored for a series of 32 cytomorphologic features. The results were evaluated using univariate and stepwise logistic regression (SLR) analyses.
In univariate analysis, 17 cytomorphologic features were identified that characterized the 40 PDTCs: insular, solid, or trabecular cytoarchitecture (P < .001); high cellularity (P = .007); necrosis (P = .025) or background debris (P = .025); plasmacytoid appearance (P = .0007); single cells (P < .0001); high nuclear/cytoplasmic ratio (P < .0001); scant cytoplasm (P = .03); nuclear atypia (P < .0001), including nuclear pleomorphism (P = .0052) and anisokaryosis (P < .0001); granular/coarse chromatin (P = .026); naked nuclei (P = .01); mitotic activity (P = .0001) and apoptosis (P < .0001); endothelial wrapping (P = .0053); and severe crowding (P < .0001). In logistic regression analysis, severe crowding (P = .0008) and cytoarchitecture (P < .0001) were identified as the most significant cytomorphologic features of PDTCs, and the combination of cytoarchitecture, severe crowding, single cells, and high nuclear/cytoplasmic ratio was the most predictive of PDTC.
PDTCs have characteristic cytomorphologic features. By using logistic regression analysis, the features that were identified as the most predictive of PDTC were severe crowding, insular/solid/trabecular morphology, single cells, and high nuclear/cytoplasmic ratio. Cancer (Cancer Cytopathol) 2009. © 2009 American Cancer Society.