الفهرس 
Anatomy of the thoraxOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
Lymphomas are the most common primary hematopoietic malignancy. They are heterogeneous group of lymphoid malignancies, which can be broadly divided into non-Hodgkin Lymphomas (NHL) and Hodgkin lymphoma (HL) that display different patterns of biological behavior and response to treatment.
The non-Hodgkin Lymphomas (NHL) is divided into : Diffuse Large B-cell Lymphoma (DLBCL), Follicular lymphoma, Lymphoblastic lymphoma, Mucosa-associated Lymphoid Tissue (MALT), Burkitt Lymphoma, B-cell lymphoma unclassifiable, intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma (Gray zone). The NHL has a great tendency to spread extra nodal. The 5-year relative survival rate of patients with NHL is approximately 63%. The survival rate has steadily improved over the last 2 decades, thanks to improvements in medical care, novel therapeutic strategies, validation of biomarkers of response, and the implementation of tailored treatment.
The Hodgkin lymphoma (HL) is divided into : Nodular lymphocyte predominant HL (NLPHL), Classic HL (CHL), Nodular sclerosis classical HL (NSCHL) grades 1 and 2, Lymphocyte-rich classic HL (LRCHL), Mixed cellularity HL (MCCHL) , Lymphocyte-depleted HL (LDCHL). EBV infection increases the risk of CHL by 3-4 fold & HIV-infected individuals have an up to 10-fold increase in incidence of CHL.
Thoracic lymphomas are characterized by enlargement of mediastinal lymph nodes. Spread to chest wall, Pleura , lung parenchyma & pericardium may occur.
CT is the most commonly used imaging modality for staging malignant lymphoma because of its widespread availability and relatively low cost. CT fails to detect lesions in normal- sized lymph nodes & is not reliable in the detection of bone marrow disease, which if present, indicates stage IV disease.
The FDG-PET can detect metabolic changes in areas involved with lymphoma before structural changes become visible. Also, it can detect focal bone marrow involvement that would be missed by bone marrow biopsy or CT.
Once intracellular, glucose and FDG are phosphorylated by hexokinase as the first step toward glycolysis. Normally, phosphorylated glucose continues along the glycolytic pathway for energy production. FDG however cannot enter glycolysis and becomes effectively trapped intracellularly as FDG-6-Phosphate. Lymphoma cells are highly metabolically active (high mitotic rates), and favor the more inefficient anaerobic pathway adding to the already increased glucose demands. These combined mechanisms allow for lymphoma cells to uptake and retain higher levels of FDG when compared to normal tissues. The distribution of fluorine 18 fluorodeoxyglucose (FDG), an analogue of glucose accumulates in tumor cells in a greater amount than it does in normal tissue.
It also is considered mandatory to perform a pretreatment FDG-PET scan in these variably FDG avid NHLs; comparison of a post-treatment FDG-PET scan to a pretreatment FDG-PET scan will lead to more accurate restaging.
18F-fludeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) plays an important role in diagnosing, staging, restaging , planning appropriate treatment strategies, monitoring therapy, and detecting recurrence of lymphoma. It also used to detect nodal & extra-nodal lymphoma.
FDG PET/CT has been found to be superior to CT and PET in initial staging of both nodal and extra nodal lymphoma. It is also superior to CT and PET in monitoring response to treatment and assessment of residual masses. FDG-PET has the ability to detect metabolic changes in areas involved with lymphoma before structural changes become visible. FDG-PET/CT fusion allows more accurate localization of foci with increased FDG uptake than PET alone. PET-CT is useful in assessing the response to treatment. In addition, it can detect disease relapse in normal size lymph nodes or within an unexpected extra-nodal site.
To conclude, FDG-PET/CT fusion is superior to CT alone and FDG-PET alone in initial staging and restaging of malignant lymphoma, as PET-CT provides the needed information about both the metabolic activity as well as the anatomical location of the neoplasm combining the advantages of both conventional methods CT and PET. Also it has an important role in detecting the response to treatment & follow up.
The Hodgkin lymphoma (HL) is divided into : Nodular