Clinicopathological Study, Morphological Subtypes and BRAF Expression in Anaplastic Thyroid Carcinoma

Aim: Anaplastic thyroid carcinoma (ATC) is highly aggressive, comprises <4% with dismal prognosis. This study examines the clinical, pathological, prognostic features and outcomes. Methods: We retrospectively analysed 15 cases of ATC over 6-years. Clinicopathological data, immunohistochemistry, morphological subtypes, treatment and survival were assessed using Kaplan-Meier curves. Results: The mean age was 66.1 years, with female predominance (M:F=1:2). Commonest symptom included neck swelling. 33.3% had long-standing goitre with rapid enlargement and 80% presented with tumours >5cm exhibiting local invasion (80%), distant metastasis (60%), particularly to the lungs (53.3%) and bones (26.6%). Histological subtypes included epithelioid (33.3%), sarcomatoid (33.3%), squamous (26.6%) and pleomorphic/ rhabdoid (6.6%) with coexisting differentiated thyroid carcinoma (DTC) noted in 46.6%. Epithelioid and squamous ATC showed higher association with DTC and exhibited high tumour infiltrating lymphocytes. Immunohistochemistry revealed PAX8(66.6%), p53(73.3%) and BRAF (53.3%) positivity; latter showing expression in epithelioid (26.6%) and squamous (13.3%) ATC. Two patients with BRAF associated squamous ATC arising from papillary thyroid carcinoma precursor showed prolonged survival. The median overall survival was one month. Conclusions: ATC is an aggressive thyroid malignancy with poor outcomes. Histological subtype and BRAFV600E status may aid in prognostication and targeted therapy selection.