Usefulness of pet and mri for the study of mediastinal lymphadenopathy

Abstract

Mediastinal lymphadenopathy is defined as an increase in the volume of mediastinal lymph nodes. Often their discovery is made in a casual way through a radiological study of the thorax. It can not be considered a disease in itself, but a manifestation of another entity, whose differential diagnosis includes various diseases and whose treatment and prognosis will depend on the underlying cause. Therefore, given this finding, we must resort to different studies that confirm the nature of the process. The methods we currently have for the study of mediastinal lymphadenopathy are computed tomography (ct) and positron emission tomography with f-18-2-fluoro-2-deoxyglucose (18fdg-pet) and its results must be confirmed histologically through invasive methods such as respiratory and digestive endoscopies and mediastinoscopy. Invasive techniques are considered as a reference for the diagnostic confirmation of mediastinal lymphadenopathy because it has a sensitivity and specificity of 80-90%. However, they carry a greater economic cost and their morbidity and mortality is not negligible. Techniques include endoscopic exploration, both respiratory and digestive, to obtain a cytohistological sample of mediastinal lymph nodes through fine needle aspiration (fna). For many years, mediastinoscopy has been the reference technique for the study of mediastinal lymphadenopathy. However, minimally invasive explorations, such as those mentioned above, have been less important because they present a comparable diagnostic performance with the advantage of being less bloody, ambulatory, with a lower complication rate and lower economic cost. To date, magnetic resonance imaging (mri) has not been used in the routine study of mediastinal lymphadenopathy. However, in recent years some studies have suggested that the use of specific mr sequences (stir and dwi) could be useful in differentiating pathological and non-pathological lymph nodes. The number of patients included in these studies is low and they are fundamentally oriented towards discrimination between metastatic and non-metastatic lymph nodes. To date, there are no studies evaluating the cost-effectiveness of mri in the diagnosis of other pathologies in relation to other pathologies that also present with mediastinal lymphadenopathy (sarcoidosis, tuberculosis, lymphoma ...). Our hypothesis is that mri may be useful in the differentiation of pathological mediastinal lymph nodes from non-pathological lymph nodes with a sensitivity and specificity superior to that of other methods commonly used in clinical practice. The aim of our study was to check the usefulness of pet and the dwi-mri sequence compared to conventional tests (ct and / or pet) in the study of mediastinic adenopathies. We will carry out an observational study of patients older than 18 years with radiological finding of mediastinal lymph nodes greater than 1 cm and / or pathological characteristics (smaller size but with necrosis or pathological distribution data). They will be studied according to the usual clinical practice, which is commonly accepted. The protocol will be modified to perform an mri (dwi sequence), upon request of informed consent. All procedures required for the study will be conducted in c.H.U. Santiago de compostela according to the available diagnostic and therapeutic methods. Patients younger than 18 years, those who do not sign consent, those who present a contraindication to mri, or a diagnosis of stage iv neoplasia, will be excluded. In all cases the etiology of the lymph nodes will be confirmed by histological study to establish a certainty diagnosis.