Primary Squamous Cell Carcinoma of the Thyroid Gland. A extremely uncommon entity with a challenging management

Clinical Case

Primary Squamous Cell Carcinomas represent 0.2- 1% of all thyroid cancers. They are likely to appear in the 5th-6th decade and are slightly more frequent in women. Usually they are diagnosed when the disease is locally advanced due to its rapid growth. The differential diagnosis can be extremely difficult because there are a number of more frequent conditions (especially upper respiratory and digestive malignancies) that should be ruled out. Pathology features include classic pavement cells and keratin depots. However immunohystochemical determinations (CK7, CK19, thyroglobulin, TTF-1, p53 positive and CK20 and calcitonin negative) confirm the diagnosis. Unfortunately, this is a condition that requires aggressive and multimodal treatment. Nevertheless, there are currently no standardized treatment strategies. We present the case of a 75-year-old male that was referred for surgical evaluation after a fast-growing thyroid mass was detected. He also complained of chronic cough and occasional dysphonia. All laboratory tests (including tumoral markers and thyroid function tests) were normal. Preoperative Doppler-US and CT-scan , a 5 cm diameter solid mass in the left thyroid lobe was detected, with a cystic appearance, several necrosis areas and multiple calcifications as well as intrathoracic component, compressing and displacing laterally both the airway and the esophagus. Preoperative laryngoscopy and bronchoscopy ruled out the presence of malignancy and total thyroidectomy plus a central lymph-node dissection were proposed. The mass was approached via an extended Kocher cervicotomy. A 8x6cm abscessified mass was found at the lower pole of the Left Thyroid Lobe. Both punction and microbial cultures were performed. Total thyroidectomy plus central lymph-node dissection were carried out. The pathology report confirmed the presence of a Primary Squamous Cell Carcinoma (T3 N0 Mx) that was positive for Cytokeratin (CK7), Thyroglobulin and TTF-1. The patient also received radiotherapy (60 days during 6 weeks) plus 5-Fluorouracil and Cysplatin. Primary Squamous Cell Carcinomas are tumors with three possible origins: Embryological rests (including the ultimobranchial body, thymus and Solid nest cells); Thyroglossal duct remnants and Metaplasia from follicular, papillary, anaplasic carcinomas. Hence, the association between the tall-cell variant of papillary carcinomas and SCC is particularly frequent. There is no standardized treatment and due to its rapid growth its prognosis is very poor, with an overall survival of about 15 months. If resection is possible, total thyroidectomy should be attempted. Moreover, although there is no consensus about the true benefit of lymphadenectomy, longer survival has been reported when it was also performed. SCC have a very selective response to chemotherapy, 5- Fluorouracil and Cysplatin being the preferred regimen. Both pre and postoperative radiotherapy has been related to longer survival.