Although patients with a history of Hodgkin lymphoma have an increased risk of developing thyroid cancer, the overall incidence is still low. This risk is particularly high in women who received radiation therapy for their disease before the age of 20. Lymphoma is a type of cancer in which lymphocytes, which are blood cells that fight infection, become cancerous. Thyroid lymphoma is a rare form of cancer that accounts for 1-2% of all thyroid cancers and 1-2% of all lymphomas outside the lymph nodes.
Most patients are older, with an average age in the late 60s. If diagnosed and treated correctly, the prognosis is usually very good. Double primary malignancies (DPM) are uncommon, although their incidence has been increasing in recent years. In patients with DPM, two different types of primary malignancies occur at the same time or successively.
Cases without a history of invasive tumors are classified as the index type. DPMs are classified as metachronous or synchronous depending on the time interval between the two tumors. Both lymphoma and thyroid cancer are relatively common individually, but thyroid gland lymphoma is also frequently found, while its joint presentation is more unusual. Secondary thyroid malignancies have been linked to previous chemotherapy and radiation therapy in patients with Hodgkin's lymphoma (HL). The development of secondary thyroid cancer may be due to genetic predisposition to cancer, exposure to environmental risk factors, or previous treatment with genotoxic agents.
However, the synchronous presentation of these two types of malignancies is exceptional. The clinical features and treatment outcomes for synchronous lymphoma and thyroid cancer remain unclear. The topic of synchronous thyroid cancer and lymphoma has been raised since 1997 by Morata et al., and some cases have been published since then. However, most of these studies are case reports, so the clinical features of the synchronous presentation of these two types of malignant tumors need further explanation. In this study, we retrospectively analyzed the clinical characteristics and treatment outcomes of eight cases of synchronous lymphoma and thyroid cancer diagnosed in our hospital. PCT and Hodgkin's lymphoma do not share the same factors.
A genetic origin is still possible, but so far no mutation has been revealed linking these two cancers. Many mutations have been implicated in the development of these tumors separately; for example, the BRAF mutation described in TPC and numerous non-Hodgkin's lymphomas have never been described in LH. Therefore, the existence of these entities and these rare events could be used for the molecular diagnosis of a common oncogenic origin. Primary thyroid lymphoma can be defined as a lymphoma that arises from the thyroid gland; this definition excludes those that invade the thyroid gland as a result of metastasis or direct extension. Primary thyroid lymphomas are almost always non-Hodgkin's lymphomas (NHL).Primary thyroid Hodgkin lymphoma is extremely rare.
Thyroid lymphoma is a rare form of cancer that accounts for 1-2% of all thyroid cancers and less than 2% of all lymphomas. Thyroid lymphomas are usually classified as non-Hodgkin B-cell lymphomas, although Hodgkin lymphoma of the thyroid has also been identified. Primary thyroid lymphoma should be suspected in patients with a rapidly increasing neck mass, especially in women with Hashimoto's thyroiditis. Certain ultrasound features, such as improved posterior echoes, may suggest the diagnosis, but eventually a biopsy is needed to confirm it. With advances in immunophenotypic analysis, fine-needle aspiration can be used for diagnosis in experienced hands.
The most common type of primary thyroid lymphoma is diffuse large B-cell lymphoma (LDCBG), which behaves more aggressively than mucosa-associated lymphoid tissue (MALT) lymphoma. Radiation therapy may be used to treat localized MALT lymphoma, but a combination of chemotherapy and radiation is needed for disseminated disease or aggressive histological subtypes. Onal et al. examined treatment outcomes among 60 patients with aggressive PTL and 27 patients with indolent disease; all had stage IE or IIE disease. Among those with aggressive lymphoma, MTC significantly improved overall survival (OS), disease-free survival, and local control over RT or chemotherapy alone.
The addition of rituximab to CHOP improved OS compared to CHOP alone (92% vs 71%; P %3D).The findings of Doria et al., among 211 patients with stage IE and IIE PTL of various histological subtypes, showed that MTC significantly decreased distant and global relapse rates; overall relapse rates were 7.7%, 37.1%, and 43% for CMT, RT alone, and chemotherapy alone respectively (P %3D). In a retrospective analysis by Ha et al., most patients reviewed had LDCBG and were treated only with surgery, surgery followed by RT, chemotherapy alone or CMT. The failure-free survival rates at 5 and 10 years were 76%, 50%, and 91% for those treated with surgery plus RT, chemotherapy alone and CMT respectively; this supports the role of CMT in those with aggressive histological subtypes (P %3D). Of the four patients treated with surgery alone, three developed recurrence. Although the tumors treated were not primary thyroid subtype tumors, extrapolation can be done from prospective and randomized NHL studies. In this study involving 401 patients with stage I or II NHLs of various histological subtypes, subjects were randomly assigned to treatment with CHOP alone or CHOP plus RT; those treated with CHOP plus RT had significantly better progression-free survival than those treated with CHOP alone (77% vs 64%; P %3D).PTL is a rare cause of thyroid malignancy and extranodal lymphomas; it should be suspected when a patient has an enlarged cervical mass, especially if they have a history of Hashimoto's thyroiditis.
Certain ultrasound features may suggest PTL such as improvement in posterior echoes; however, diagnosis must ultimately be made by biopsy. With improvements in immunophenotypic techniques AAF can be used as an initial diagnostic test in centers where experienced physicians perform the procedure and interpret cytology results; however if there is any doubt about diagnosis an open surgical biopsy should be performed for confirmation. The most common subtype of PTL is LDCBG which is distinguished by its aggressive behavior; radiation therapy may be used to treat localized MALT lymphomas but combination chemotherapy and radiation therapy is needed for disseminated disease or aggressive histological subtypes. In conclusion there appears to be a relationship between thyroid cancer and certain types of lymphomas; however further research needs to be done to better understand this relationship.
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