ODP454 A Middle Aged Woman With a Thyroid Cyst: A Case of Squamous Cell Carcinoma of the Thyroid

Abstract

Background Squamous cell carcinoma of the thyroid (SCCT) is a very rare malignant neoplasm of the thyroid with distinct squamous differentiation of tumor cells. Only 84 cases of primary SCCT were diagnosed worldwide up until 2012. The number has now increased to around 200. The incidence of SCCT is less than 1% out of all thyroid malignancies, but it has one of the fastest increasing incidences of cancer worldwide 1 . With no standard consensus to guide the management plan and 3 year survival rate of 43%, primary SCCT is challenging to treat 1 . Here we describe a case of primary SCCT. Case Summary A 65 year old white female with a medical history of longstanding Hashimoto's thyroiditis on Levothyroxine was initially evaluated for left neck enlargement and compressive symptoms. She had no significant risk factors for malignancy. TFTs were normal on Levothyroxine 100 mcg daily. CT neck showed a left thyroid cyst measuring 4.4×7 cm. Biopsy showed cystic material. Left hemithyroidectomy pathology showed moderately differentiated squamous cell carcinoma stage pT3aN0a, 4.5 cm without lymph node involvement. The cells stained positive for p40, Ck5/6, p63 and TTF1, but negative for thyroglobulin and calcitonin. Subsequently, completion thyroidectomy with central lymph node dissection resulted in benign pathology. Postoperative imaging was without evidence of residual neoplasm or pathologic cervical adenopathy. Levothyroxine was continued to maintain a TSH in the normal range. SCCT is not radioiodine avid and is therefore resistant to I-131 treatment. For this reason, the patient was referred to radiation-oncology and completed 6 weeks of XRT. Oncology recommended supportive care due to the aggressive nature of this tumor subtype. Conclusion SCCT is a very rare cancer of the thyroid with a mortality rate of 57% at 3 years. Overall survival rate, although poor, is dependent on the extent of the tumor resection and adjuvant radiotherapy/chemotherapy. Experts predict a 6 month average life expectancy with SCCT. At the time of this abstract, there is no evidence of recurrence or metastasis for our patient. There are no official guidelines on the diagnosis and treatment of SCCT, and more research is needed to better manage this rare cancer. Reference: 1. Primary Squamous Cell Carcinoma of the Thyroid Gland. Mohd-Irman-Shah Ibrahim et al. Iranian Journal of Otorhinolaryngology 2018 Jan; 30(96): 65–68 Presentation: No date and time listed