SAT-376 - Rapidly Progressive Insular Thyroid Carcinoma Presenting with Compressive Symptoms and Extensive Cervical Lymphadenopathy

Background:
Insular thyroid carcinoma, a subtype of poorly differentiated thyroid carcinoma (PDTC), is a rare and aggressive malignancy with clinical behavior intermediate between differentiated and anaplastic thyroid cancer. It is defined by solid/insular growth, increased mitotic activity, tumor necrosis, and frequent angioinvasion, often resulting in rapid locoregional progression and limited responsiveness to radioactive iodine (RAI).
Clinical

Case:
A 52-year-old man presented with a one-week history of a rapidly enlarging right-sided neck mass associated with odynophagia, dysphonia, mild dyspnea, and otalgia. Computed tomography revealed bilateral cervical lymphadenopathy (largest 2 cm) and an 8 cm heterogeneous right thyroid mass causing tracheal deviation. Fine-needle aspiration demonstrated a high-grade carcinoma with marked cytologic atypia, raising concern for poorly differentiated, medullary, or anaplastic carcinoma. FDG PET/CT showed intense uptake in the thyroid mass and bilateral upper cervical lymph nodes without distant metastases. The patient underwent total thyroidectomy with central neck dissection and bilateral level II–IV neck dissections. Pathology revealed an 8 cm insular carcinoma with solid growth pattern, extensive angiolymphatic invasion, and nodal metastases, along with an incidental 0.2 cm papillary thyroid microcarcinoma. Postoperative calcium levels remained normal.

Discussion:
This case illustrates classic clinical and histopathologic features of insular thyroid carcinoma, including rapid symptom progression and extensive locoregional disease. Per ATA risk stratification, this represents high-risk thyroid cancer. Given reduced RAI avidity typical of PDTC, adjuvant therapy often requires individualized consideration of RAI, external beam radiation, and systemic therapy within a multidisciplinary framework.

Conclusion:
Early recognition of insular thyroid carcinoma is essential to guide aggressive surgical and risk-adapted postoperative management aimed at reducing recurrence and disease-related mortality.

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