Nodal status of malignant lymphoma in pelvic and retroperitoneal lymphatic pathways: PET/CT.

Nodal involvement of abdominal lymphatic pathways occurs in a number of histologic subtypes of malignant lymphoma. The histologic diagnosis of abnormal uptake in abdominal lymphatic pathways includes mainly non-Hodgkin lymphoma with B-cell lineage and Hodgkin lymphoma. Initial involvement of pelvic and retroperitoneal lymphatic pathways can result from a variety of underlying non-Hodgkin's lymphoma: follicular lymphoma, diffuse large B-cell lymphoma, marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type, and mantle cell lymphoma. The diagnosis of these clinical entities requires various imaging techniques, including fluorine-18-fluorodeoxyglucose ((18)FDG) positron emission tomography/computed tomography (PET/CT), computed tomography, (67)Gallium scintigraphy, and magnetic resonance imaging (MRI). Specific symptoms of these diseases are often lacking, but intense (18)FDG accumulation on PET/CT may be a marker of disease activity. Interpretation of the presence of and the specific pattern of (18)FDG uptake may obviate the need for invasive biopsy. However, distinction of abnormal uptake is often difficult to determine because focal accumulation of (18)FDG in the urinary tract or intestine mimics nodal involvement in the pelvic and retroperitoneal lymphatic pathways. In this review, specific conditions causing nodal involvement of pelvic and retroperitoneal lymphatic pathways in patients with malignant lymphoma that may impact diagnostic and treatment decisions are highlighted.