[Malignant lymphoma of the thyroid gland]

Malignant lymphoma of the thyroid gland can be defined as a lymphoma arising from the thyroid gland. Lymphomas of the thyroid gland represent less than 5% of primary thyroid neoplasms and are two to three times more common in women than in men, whereas the median age is usually close to 60 years. Majority of thyroid lymphomas are diffuse, large-cell lymphomas. The incidence of thyroid lymphomas in patients with Hashimoto thyroiditis has markedly increased and this phenomenon is probably related to their pathogenesis.

Unlike most other thyroid neoplasms, lymphomas are usually rapidly enlarging masses and local symptoms are common: pain, hoarseness, dysphagia, and dyspnea or stridor.

To evaluate the extent of disease, a chest x-ray and CT scans of the head and neck, chest, abdomen, and pelvis are necessary. An excisional or large-needle biopsy may also be necessary to make the correct diagnosis. Occasionally, these tumors can be confused with anaplastic thyroid carcinomas, which can lead to serious mistakes in management. A gallium scan or a positron emission tomography (PET) scan can help later to establish whether any residual abnormality, observed on x-ray studies after treatment, contains active lymphoma or scar tissue. After diagnosis, patients are clinically staged (without surgery) using appropriate computed tomography scans or magnetic resonance imaging.

Assessment of the extent of thyroid lymphomas is crucial for prognosis and treatment. Total thyroidectomy may improve the prognosis in patients with intrathyroidal disease only. It is very important to identify patients with favorable prognostic factors and to treat them with standard chemotherapy (CHOP) and radiotherapy protocols. Patients with diffuse large-cell primary thyroid lymphomas should not be treated with radiation therapy alone.

The best treatment results for malignant lymphomas of the thyroid gland are achieved using a combined-modality therapy.