Primary thyroid lymphoma (PTL) is very rarely encountered in clinical practice, as it comprises less than 5% of all malignancies that arise from this organ [1] [2] [3]. Lymphomas that develop in the thyroid are almost always of B-cell origin, the most common being diffuse large B-cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma, while follicular lymphoma, small lymphocytic lymphoma, Burkitt's lymphoma and Hodgkin's lymphoma are other recognized forms [1] [3]. PTL is principally diagnosed in the sixth and seventh decades of life, and a significant predilection toward female gender has been established [1] [2] [4] [5]. Furthermore, a markedly higher number of PTLs are diagnosed in patients with preexisting Hashimoto's thyroiditis, implying its important role in the pathogenesis of PTL [1] [3] [5] [6]. An enlarging painless mass in the neck, seen in almost 70% of cases, is the main clinical manifestation of PTL, and the mass can compress the adjacent structures in the neck, resulting in dysphagia, dyspnea, stridor, and hoarseness in 30-50% of patients [3] [4] [6]. In addition, constitutional symptoms of fever, weight loss, and night sweats, which are typical for B-cell lymphomas, may be present as well but are reported in only 10% of individuals [2] [3].

Many reports have emphasized the benefit of early recognition of PTL, primarily because therapy is quite effective in its earlier stages [1] [2] [4] [5]. However, studies have shown that up to 36 months may pass from the onset of symptoms to the diagnosis, which markedly affects survival rates and treatment outcomes [1] [2] [3] [4] [5]. For this reason, a meticulous clinical workup must be performed in order to obtain enough evidence to raise clinical suspicion toward PTL. Firstly, patients should be asked about the course and progression of symptoms, whereas a detailed physical examination of the neck can result in palpation of a hard and smooth-surfaced mass [4]. If a mass is palpated, immediate employment of imaging techniques, such as ultrasonography (US), is necessary, and a hypoechoic homogeneous mass with an enhanced posterior echoes is highly suggestive of PTL [2] [4]. Based on US findings, PTL is further divided into nodular (unilateral and pseudocystic changes), diffuse (bilateral and possessing indistinct borders) and mixed, which shows multiple patchy lesions [4]. Because the diagnosis is not conclusive without a histopathological examination, a biopsy of the lesion, most commonly in the form of fine-needle aspiration (although core-incision and open biopsy are mentioned as possible methods as well), is the vital step in workup [1]. Not only does it confirm the diagnosis, but it also helps in determining the stage of the tumor, together with computed tomography (CT) and other imaging modalities [1] [2] [4] [5] [6]. Based on the extent of tumor involvement and its dissemination, PTL is classified into [3]:

• Stage I - Only local growth is observed.
• Stage II - Dissemination into the lymphatic system within the same side of the diaphragm.
• Stage III - Infiltration of distant lymph nodes and/or spleen.
• Stage IV - The presence of distant metastases.

The treatment of thyroid lymphoma depends on the stage and type of lymphoma. The most common treatment approach is chemotherapy, often combined with radiation therapy. Rituximab, a monoclonal antibody targeting a specific protein on B-cells, is frequently used in combination with chemotherapy. In some cases, surgery may be performed to relieve symptoms or if the diagnosis is uncertain. The treatment plan is usually tailored to the individual patient, considering factors such as age, overall health, and specific characteristics of the lymphoma.

The prognosis for thyroid lymphoma varies depending on several factors, including the type and stage of the lymphoma at diagnosis. Generally, patients with localized disease have a better prognosis than those with more advanced disease. The overall survival rate for thyroid lymphoma is relatively favorable compared to other types of thyroid cancer, especially when diagnosed early and treated appropriately. However, the prognosis can be poorer for patients with aggressive forms of lymphoma or those with significant systemic symptoms.

The exact cause of thyroid lymphoma is not well understood, but it is believed to be related to chronic inflammation of the thyroid gland. Hashimoto's thyroiditis, an autoimmune condition where the immune system attacks the thyroid, is a known risk factor. This chronic inflammation may lead to changes in the lymphocytes, eventually resulting in lymphoma. Other risk factors may include age, with most cases occurring in older adults, and a history of other autoimmune diseases.

Thyroid lymphoma is a rare disease, with an incidence of about 2 cases per million people per year. It is more common in women than men, likely due to the higher prevalence of autoimmune thyroid diseases in females. The disease typically affects older adults, with most cases diagnosed in individuals over the age of 60. The association with Hashimoto's thyroiditis is significant, as many patients with thyroid lymphoma have a history of this autoimmune condition.

The pathophysiology of thyroid lymphoma involves the transformation of normal lymphocytes into malignant cells. This process is often associated with chronic inflammation, as seen in conditions like Hashimoto's thyroiditis. Over time, the persistent immune response can lead to genetic mutations in the lymphocytes, causing them to grow uncontrollably and form a tumor. The exact molecular mechanisms are complex and involve various genetic and environmental factors.

There are no specific measures to prevent thyroid lymphoma, primarily due to its rarity and the unclear etiology. However, managing underlying conditions like Hashimoto's thyroiditis may help reduce the risk. Regular monitoring and treatment of autoimmune thyroid diseases can potentially minimize chronic inflammation, which is a known risk factor for developing lymphoma. Maintaining a healthy lifestyle and regular medical check-ups may also contribute to overall well-being and early detection of any thyroid abnormalities.

Thyroid lymphoma is a rare and distinct type of cancer that arises from the lymphocytes within the thyroid gland. It is often associated with autoimmune thyroid conditions like Hashimoto's thyroiditis. Patients typically present with a rapidly enlarging neck mass and may experience symptoms related to compression of nearby structures. Diagnosis involves imaging and biopsy, while treatment usually includes chemotherapy and radiation. The prognosis is generally favorable, especially with early detection and appropriate treatment.

If you or someone you know is experiencing symptoms such as a rapidly growing neck mass, difficulty swallowing, or breathing problems, it is important to seek medical evaluation. Thyroid lymphoma is a rare condition, but early diagnosis and treatment can significantly improve outcomes. Understanding the potential link between autoimmune thyroid diseases and lymphoma can help in recognizing symptoms early. Regular check-ups and monitoring of thyroid health are essential, especially for individuals with a history of thyroiditis or other autoimmune conditions.

1. Gupta N, Nijhawan R, Srinivasan R, et al. Fine needle aspiration cytology of primary thyroid lymphoma: a report of ten cases. Cytojournal. 2005;2:21.
2. Xia Y, Wang L, Jiang Y, Dai Q, Li X, Li W. Sonographic Appearance of Primary Thyroid Lymphoma-Preliminary Experience. Björklund P, ed. PLoS One. 2014;9(12):e114080.
3. Peixoto R, Correia Pinto J, Soares V, Koch P, Taveira Gomes A. Primary thyroid lymphoma: A case report and review of the literature. Annals of Medicine and Surgery. 2017;13:29-33.
4. Stein SA, Wartofsky L. Primary thyroid lymphoma: a clinical review. J Clin Endocrinol Metab. 2013;98(8):3131-3138.
5. Verma D, Puri V, Agarwal S, Bhaskar A. Primary thyroid lymphoma: A rare disease. J Cytol. 2014;31(4):218-220.
6. Lee SC, Hong SW, Lee YS, et al. Primary thyroid mucosa-associated lymphoid tissue lymphoma; a clinicopathological study of seven cases. J Korean Surg Soc. 2011;81(6):374-379.