Poorly differentiated thyroid carcinoma: A hospital-based clinicopathological study and review of literature

INTRODUCTION: Poorly differentiated thyroid carcinoma (PDTC) is a rare aggressive malignancy of thyroid follicular cells and has unique features in morphology and behavior. This study was aimed to describe the experience of a tertiary medical center with PDTC within a 10-year period.

MATERIALS AND METHODS: This is a descriptive retrospective study of eight cases of PDTC among 418 various thyroid carcinomas. All cases of PDTC were retrieved along with the clinicopathological information.

RESULTS: Only eight cases (1.9%) of PDTC were diagnosed among 418 thyroid carcinomas. Mean age was 48.12 with 3:5 (male:female) and tumor size ranged 3-12 cm. PDTC were diagnosed coexisting with one or more other pathologies; nodular hyperplasia (four cases), papillary carcinoma (one case), follicular carcinoma (three cases), and Hashimoto thyroiditis (two cases); with ≥60% PDTC component. Six cases associated with high-grade features died within 3 years after diagnosis.

DISCUSSION: Mean age in this study was younger including a 20-year-old girl. Younger age was associated with better prognosis. Most of the cases had underlying benign thyroid lesions and differentiated thyroid carcinoma. Most of the PDTC had poor prognosis associated with PDTC component ≥60%, tumor necrosis, high mitotic count, lymph node involvement, vascular invasion and distant metastasis; and these cases died within 3 years after diagnosis.

CONCLUSION: Although treatment of PDTC remains surgery followed by radioiodine therapy, correct histopathological diagnosis is important for clinicians and oncologists to predict the prognosis. All thyroid carcinoma should be sampled thoroughly not to miss small foci of PDTC component.