An Unusual Case of Coexistence:De-Differentiation of a Papillary Thyroid Carcinoma into SquamousCell Carcinoma

Abstract

Background: Squamous cell carcinoma (SCC) of the thyroid is a rare condition comprising less than 1% of thyroid cancer. SCC of the thyroid may arise from de-differentiation of aggressive thyroid carcinomas secondary to chronic thyroid gland inflammation1. Thyroid SCC is a variant of undifferentiated thyroid carcinoma and is also associated with tall-cell variant of Papillary thyroid carcinoma (PTC). Given its aggressive clinical course, early recognition of the disease is essential to management. Clinical Case: A 67-year-old, Filipino male, presented with anterior neck mass over a period of 11-months. He was clinically euthyroid. Neck ultrasound showed enlarged thyroid gland with hypoechoic left thyroid nodule (1.9cm x 1.2cm) where fine needle aspiration biopsy showed a colloid nodule. Patient then manifested with compressive symptoms, undocumented weight loss and easy fatigability. He had total thyroidectomy with histopathology consistent with Diffuse Sclerosing Variant of PTC with Squamous Differentiation, arising from chronic lymphocytic thyroiditis with extra-thyroidal extension. Immunohistochemical markers showed (+) TTF-1, (+) HBME-1 and (+) PAX – 8. Two months after thyroidectomy, he noticed palpable cervical nodes and hoarseness of voice. PET-CT scan showed hypermetabolism in the thyroid bed and tumor recurrence with 2 FDG-avid lymph nodes, on Level III with SUVS up to 8.5. RAI imaging showed functioning thyroid tissues. Patient had completion thyroidectomy with selective neck dissection within 3 months after initial surgery. Histopathology revealed Keratinizing Squamous Cell Carcinoma metastatic to lymph nodes. Molecular studies were not pursued by patient. Repeat PET/CT Scan showed rapid tumor recurrence in the left thyroid bed with strap muscle and thyroid cartilage infiltration, as well as cervical lymph node invasion. PEG insertion and prophylactic tracheostomy addressed nutritional status and airway protection, respectively. He was treated with course of external beam radiation (60 Gy in 33 fractions). He had concurrent chemotherapy with Carboplatin-Paclitaxel regimen for only 2 cycles. After 13 months of initial presentation, patient eventually succumbed to cardiac arrest. Conclusion: This transformation of the thyroid is a malignancy with high mortality, with average survival length of only less than a year. Combined modality with surgery, radiotherapy and chemotherapy to prevent disease progression and local recurrence is needed. Multidisciplinary approach is significant in the management due to its poor survival rate. References: (1)Hararah KM, Gertz JR, Sippel SR, et. Al. (2015) De-differentiation of Conventional Papillary Thyroid Carcinoma into Squamous Cell Carcinoma. Thyroid Disorders Ther 4: 192. doi:10.4172/2167-7948.1000192