High Grade Differentiated Follicular Cell-Derived Thyroid Carcinoma Versus Poorly Differentiated Thyroid Carcinoma: A Clinicopathologic Analysis of 41 Cases

AbstractCriteria overlap for separating between malignant follicular epithelial cell-derived thyroid gland neoplasms with high grade features of increased mitoses and tumor necrosis but lacking anaplastic histology. Patterns of growth, nuclear features, tumor necrosis, and various mitotic index cutoffs are suggested, but a reproducible Ki-67-based labeling index has not been established. Forty-one cases diagnosed as poorly differentiated thyroid carcinoma (PDTC) or high grade differentiated follicular cell-derived thyroid carcinoma (HGDFCDTC) were reviewed, with histologic features, mitotic figure counts, and Ki-67 labeling index reviewed on cases within Southern California Permanente Medical Group from 2010 to 2021 to establish any potential outcome differences. There were 17 HGDFCDTC (nine papillary thyroid carcinoma; eight oncocytic follicular thyroid carcinoma), median age 64  years, affecting nine females and eight males. Tumors were large (median, 6.0 cm), usually unifocal (n = 13), with only one tumor lacking invasion. Tumor necrosis was present in all; median mitotic count was 5/2 mm2 (median Ki-67 labeling index 8.3%). Three patients had metastatic disease at presentation, with additional metastases in four patients (41.2% developed metastases); 11 were without evidence of disease (median 21.2  months); with the remaining six patients alive (n = 4) or dead (n = 2) with metastatic disease (median 25.8 months). Criteria associated with an increased risk...
Source: Endocrine Pathology - Category: Pathology Source Type: research