Cytomorphologic features of poorly differentiated thyroid carcinoma

Abstract

BACKGROUND: 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). METHODS: 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. RESULTS: In univariate analysis, 17 cytomorphologic features were identified that characterized the 40 PDTCs: insular, solid, or trabecular cytoarchitecture (P < .001); high cellularity (P ¼ .007); necrosis (P ¼ .025) or background debris (P ¼ .025); plasmacytoid appearance (P ¼ .0007); single cells (P < .0001); high nuclear/cytoplasmic ratio (P < .0001); scant cytoplasm (P ¼ .03); nuclear atypia (P < .0001), including nuclear pleomorphism (P ¼ .0052) and anisokaryosis (P < .0001); granular/coarse chromatin (P ¼ .026); naked nuclei (P ¼ .01); mitotic activity (P ¼ .0001) and apoptosis (P < .0001); endothelial wrapping (P ¼ .0053); and severe crowding (P < .0001). In logistic regression analysis, severe crowding (P ¼ .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. CONCLUSIONS: 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 ( (617) PDTCs often present at an advanced stage, have a propensity for local recurrence, and tend to metastasize to regional lymph nodes, lung, and bones. 1,6,9 Over the past 2 decades, fine-needle aspiration (FNA) biopsy (FNAB) has emerged as 1 of the most important tests for the initial evaluation of thyroid nodules and for guiding their clinical and surgical management. Because of the significant clinical impact of a diagnosis of PDTC, it would be advantageous to recognize this rare subset of thyroid cancers preoperatively in FNABs. Since the original cytologic description of 6 cases by Pietribiasi at al, 10 only a few small series 11-13 and case reports 14-25 have been published. In an effort to better define the cytomorphologic features of PDTC, we applied statistical analysis to a multi-institutional series of 40 histologically proven cases. To our knowledge, this is the largest FNAB series of PDTCs studied. MATERIALS AND METHODS Case Se...

Relative sensitivity of thyroid fine‐needle aspiration by tumor type and size

“…Although PDCAR is uncommon, characteristic cytologic features have been reported, 13 including severe crowding, insular/solid/trabecular morphology, single cells, and high nuclear/cytoplasmic ratio. These features were described from a group of PDCAR in which >90% of the tumor displayed PDCAR morphology; however, when arising in a follicular or papillary carcinoma the well-differentiated component may also (or exclusively) be sampled (as reflected by our results).…”

Update in Thyroid Fine Needle Aspiration

“…PDTC has an aggressive clinical behavior intermediate between that of WDTCs and undifferentiated (anaplastic) thyroid carcinomas [32][33][34][35][36] While PDTC represents an extremely important clinical entity, few studies have examined its cytologic features, and aspirates of PDTC represent a diagnostic challenge for the cytopathologist. One of the first cytological descriptions of PDTCs was a report of 6 cases by Pietribiasi et al [37][38][39][40][41]. In addition to these series, a limited number of published case reports are also available, but only a few FNAB cases have prospectively recognized the tumors as PDTC.…”

“…Aspirates of PDTC are typically cellular with severely crowded clusters and scant colloid although some cases can show single cells [37]. The insular type will often display a recognizable insular cytoarchitectural pattern at low magnification (Fig.…”

“…While a cytologic diagnosis of malignancy can be made in a subset of cases, for many PDTC cases, the lesion will be diagnosed as "suspicious for a follicular neoplasm." Using stepwise logistic regression analysis, a combination of insular, solid, or trabecular cytoarchitectural patterns, single cells, high N/C ratio, and severe crowding have been shown to be the most useful in combination for predicting PDTC in FNA samples [37].…”

Cytopathology of Solid Variant of Papillary Thyroid Carcinoma: Differential Diagnoses with other Thyroid Tumors

“…Hence, larger studies may help in establishing or refuting this suggestion. Further, the single-cell pattern has been defined as one of the cytological features highly predictive of PDTC by Bongiovanni et al [23] in their series of 40 cases. However, in their study, the features were compared with well-differentiated thyroid neoplasms and not with SVPTC.…”