[Malignant lymphomas (primary and secondary) of the thyroid. Description of 9 case reports and review of the literature].

Malignant lymphomas of the thyroid are rare and represent approximately 0.3 to 8.9% of thyroid malignant neoplasms. We report 9 new cases; their clinical and histopathological features are discussed and compared with those of previously published series. Malignant lymphomas of the thyroid raise a number of issues: primary or secondary origin, histological typing (50% of cases are high grade lymphomas), differential diagnosis with either Hashimoto's chronic thyroiditis (often associated with thyroid lymphomas) or genuine anaplastic carcinoma of the thyroid. Routine histological study can be complemented by immunohistochemistry.