[Squamous metaplasia in thyroid gland as histologic diagnostic pitfall: - a case report]

ABSTRACT

It is rare to find squamous metaplasia in the thyroid gland. Its existence is usually seen in association with a pathological lesion such as mucoepidermoid carcinoma, squamous cell carcinoma and diffuse sclerosing variant of papillary thyroid carcinoma. In most cases the squamous cells are few in number and squamous metaplasia is focal and small in size. Extensive squamous metaplasia of the thyroid gland is a very rare finding. We report a case of massive squamous metaplasia in Hashimoto thyroiditis in a 53 year-old- male with a four year history of hypothyroidism. Also seen in the history is impaired thyroid function tests of low T3 and T4 levels with rise in TSH. The patient currently presented with neck discomfort and a somewhat firm nodular neck mass. Ultrasonography revealed heterogeneous nodular enlargement of both thyroid lobes and a calcified nodule of the left lobe. Fine needle aspiration of the thyroid nodule was performed which reported findings suspicious for malignancy. Based on these findings the patient underwent total thyroidectomy. In this article we address the causes and sources of massive squamous metaplasia in the thyroid gland. We also discuss the histopathologic differential diagnostic lesions which could be the cause of potential pitfalls encountered in the interpretation of the cytopathology and histopathology of such lesions arising in this gland