Primary Squamous Cell Carcinoma of the Thyroid

Abstract

Primary squamous cell carcinoma of the thyroid (PSCCT) is a rare head and neck malignancy. A case of PSCCT is presented and the relevant literature reviewed. CASEA 62 year old man with no history of smoking presented with two months of hoarseness. Examination revealed a rock hard mass in the right thyroid lobe. Fiberoptic laryngoscopy demonstrated an immobile right true vocal fold and no mucosal abnormalities. Ultrasound and CT of the neck showed a 1.1 cm calcified right thyroid nodule (Figure 1). No mucosal irregularities or lymphadenopathy were evident on CT. Fine needle aspiration yielded follicular epithelial cells without malignancy. A thyroidectomy was undertaken, but the gland had an atypical appearance, and only an incisional biopsy was performed. The entire right lobe was enlarged, firm, and contained a small calcified cyst. A fibrous lesion with inflammatory cells and no malignancy was reported on frozen section. Permanent sections revealed moderately differentiated squamous cell carcinoma. Full-body PET showed intense hypermetabolic activity in the right thyroid lobe only ( Figure 2). The patient next underwent total thyroidectomy (Figure 3), and frozen sections revealed invasion of the recurrent laryngeal nerve, trachea, and the cricoid and thyroid cartilages. He later underwent total laryngectomy. Final pathology showed clear margins and no evidence of a laryngeal primary (Figure 4). Postoperatively he received 66 Gy of radiation with concurrent cisplatin. A repeat PET scan 6 months after completion of therapy showed no evidence of disease. DISCUSSION PSCCT is extremely rare, with approximately 150 cases described in the English literature. 1 Of all thyroid malignancies, only 0.7% are PSCCT. 1,2 Metastasis or direct extension of squamous cell carcinoma from adjacent structures such as the larynx, esophagus, or trachea is much more common. 3 Proposed etiologies for the development of PSCCT in a gland that normally does not contain squamous epithelium include squamous metaplasia of follicular epithelial cells in the face of chronic inflammation 4-6 , squamous differentiation of other thyroid neoplasms 7 , or the presence of embrionic rests in remnants such as the thyroglossal duct or ultimobranchial body. 8,9 Patients usually present in the 5 th to 7 th decades of life. 2,3 Several series have reported a higher incidence in women. 2,3 Presentation and course are similar to that of anaplastic thyroid carcinoma. A rapidly enlarging neck mass and hoarseness are common presenting complaints. 3 The tumors tend to be advanced at presentation and invasion of the trachea, esophagus, and recurrent laryngeal nerve is common. 1,3 Reported outcomes have been poor relative to other squamous cell carcinomas of the head and neck with few patients surviving beyond 18 months despite aggressive treatment. 3,10 The handful of reported long-term survivors underwent complete surgical excision followed by radiotherapy. 10 Although chemoradiotherapy alone has been ineffective in treating PSCCT 10 , adding chemotherapy as a r...