Primary mucinous carcinoma of the thyroid gland: case report with review of the literature.

Primary mucinous thyroid carcinoma (PMTC) are extremely rare lesions that are histologically indistinguishable from mucinous carcinoma of other sites. We describe the clinicopathological, histological and immunohistochemical features of this rare tumour with a review of the literature. We describe a case of thyroid tumour, in 56-year-old Tunisian man, composed of small nests and sheets of malignant epithelial cells associated with extensive extracellular mucin that entrapped the follicular parenchyma of thyroid. Thyroglobulin and thyroid-specific-transcription factor 1 (TTFl) were focally positive. Follow-up did not reveal another neoplasm at other sites. Based on these features, we classified this tumour as PMTC. Mucinous carcinoma of the thyroid gland can be a cause of pitfall in differential diagnosis. For correct diagnosis, complete clinical history, restricted histological criteria and immunohistochemical panel are necessary.