Introduction:
Thyroid lymphoma is a rare tumor that accounts for 5% of all thyroid neoplasms and 1 to 2% of extranodal lymphomas. The predominant histological type is diffuse large B-cell lymphoma. It mainly affects women in their sixth decade and it is manifested by a rapidly progressive cervical mass. The diagnosis is histological and treatment is essentially based on chemotherapy.
Case presentation:
Case 1: a 50-year-old female patient, with no notable pathological history, who presented with cervical swelling that has been present for 6 months and is associated with dysphagia, dyspnea, and respiratory difficulty.
The clinical examination found the patient conscious and stable on the hemodynamic and respiratory levels. Cervical examination reveals cervical swelling that is painful on palpation and mobile on swallowing.
The biological assessment found TSH at 8.71 mIU/l, free T4 at 8.64 mIU/l, and free T3 at 3.68 mIU/l, suggesting peripheral hypothyroidism. Anti-thyroperxydase antibodies were elevated at 177.88IU/ml.
Cervical ultrasound found a diffuse heterogeneous goiter associated with right supraclavicular lymphadenopathy, measuring 20 x 10 mm.
Cervicothoracic CT found a heterogeneous plunging goiter without suspicious lesions.
Case 2: a 75-year-old female patient, followed for hypertension under monotherapy, admitted for cervical swelling.
The clinical examination found the patient conscious and stable on the hemodynamic and respiratory levels. Cervical examination revealed a cervical swelling that was painful on palpation and mobile on swallowing.
The biological assessment showed a thyroid assessment without abnormalities.
Cervico-thoracic CT revealed a plunging and compressive nodular goiter starting from the left lobe associated with sub-centimeter laterocervical and mediastinal lymphadenopathy.
Both patients underwent surgical biopsy of the mass.
Results:
Histologically, the two biopsies corresponded to malignant tumor proliferation occurring mainly in diffuse layers. The tumor cells were dyscohesive, atypical, and large with hyperchromatic nuclei and clear-appearing cytoplasm. We also noted the presence of numerous mitotic figures.
The immunohistochemical study showed the following:
- Strong and diffuse positive marking of tumor cells by the anti-CD20 antibody.
- A tumor proliferation index estimated at 85% for the first case and 75% for the second case.
- Negative staining of tumor cells via anti-CK antibody and anti-CD3 antibody.
By combining clinical, radiological, histological, and immunohistochemical data, a diagnosis of diffuse large thyroid B-cell lymphoma was made for both cases.
Discussion:
Primary thyroid lymphoma (PLT) is defined as lymphoma developing from the thyroid gland and not from another area and arriving at the thyroid by contiguity or metastasis. It is generally a non-Hodgkin lymphoma, of which diffuse large B-cell lymphoma accounts for 70%, followed by B-cell non-Hodgkin lymphoma of mucosa-associated lymphoid tissue (MALT), follicular lymphoma, mantle cell lymphoma , Burkitt lymphoma, and finally angioblastic lymphoma.
A history of Hashimoto's thyroiditis is a well-recognized risk factor for developing PTL, with a relative risk of 67 compared with people without thyroiditis.
This pathology is generally manifested by rapidly progressive cervical swelling associated with signs of compression including dysphagia, dyspnea, and superior vena cava syndrome, with a deterioration in general condition and night sweats. The biological assessment found euthyroidism in patients followed for Hashimoto's thyroiditis treated with levothyroxine, and hypothyroidism in the other patients. Anti-thyroperoxidase antibodies were elevated in 60% of patients.
The use of ultrasound (US) scans can suggest a diagnosis, as the mass may be nodular, diffuse, or mixed. Common ultrasound findings include a hypoechoic solid lesion associated with hypervascularity and a diversity that characterizes its outline. Therefore, a thorough investigation is indicated in any patient with autoimmune thyroiditis who has suspicious findings on ultrasonography.
Fine needle aspiration (FNA) has become an essential tool in the management of thyroid diseases, but it has shown inconsistent results in the diagnosis of primary thyroid lymphomas; for this, core or surgical biopsies are necessary to establish a definitive diagnosis.
Histologically, LBDGC is characterized by a diffuse architecture with large B cells of variable appearance (centoblasts and immunoblasts). Tumor cells typically express CD20, PAX5, and CD79a. The tumor proliferation index (Ki67) is greater than 40%.
Primary thyroid lymphomas respond well to chemotherapy and radiotherapy. The chemotherapy regimen includes cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP). Radiation therapy is usually given after three to six cycles of chemotherapy. The prognosis depends on the stage of the disease at the time of presentation.
Conclusion:
Primary thyroid lymphoma is a rare cause of thyroid malignancy. It mainly affects women and is manifested by rapidly progressive cervical swelling. The diagnosis is histological and treatment is based on chemo-radiotherapy.
