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Primary Mediastinal Lymphoma: Characteristic Features of the Various Histological Subtypes on CT

Objective: To assess the characteristic features of the primary mediastinal lymphoma (PML) on CT and to test the relationship between CT findings and the likelihood of the 3 most common subtypes (Hodgkin lymphoma [HL], mediastinal diffuse large B-cell lymphoma [Med-DLBCL], and precursor T-cell lymphoblastic lymphoma [T-LBL]). Methods: Sixty-six consecutive patients with pathologically proven PML including 29 patients with HL, 21 with Med-DLBCL, and 16 with T-LBL underwent CT prior to therapy. CT scans were independently reviewed by 2 radiologists who were blinded to the pathologic diagnosis for the following considerations: pattern of involvement (i.e., morphologic features, mass size, and contrast enhancement pattern), and ancillary findings at other sites including neck, abdomen, and pelvis. Interobserver agreement was measured by Kappa statistics, and independent predictors were calculated using multiple logistic regression analysis for determining the likelihood of the subtypes based on CT. Results: Characteristic features of HL included irregular contour of the anterior mediastinal mass (20 of 29, 69%) and high prevalence of associated mediastinal lymphadenopathy (28 of 29, 97%). Characteristic features of Med-DLBCL included regular contour (14 of 21, 67%) and absence of cervical and abdominal lymphadenopathy (0 of 21). Characteristic features of T-LBL included regular contour (12 of 16, 75%) and high prevalence of cervical (9 of 16, 56%) and abdominal (6 of 16, 38%) lymphadenopathy and splenomegaly (11 of 16, 69%). CT findings independently associated with increased likelihood of HL were surface lobulation (P < 0.01), the absence of vascular involvement (P < 0.01), or pleural effusion (P < 0.05). The presence of vascular involvement was associated with increased likelihood of Med-DLBCL (P < 0.001). Furthermore, CT findings including the presence of cervical lymph nodes or inguinal lymph nodes (P < 0.001), the presence of pericardial effusion (P < 0.05), and the absence of surface lobulation (P < 0.05) were significantly associated with the likelihood of T-LBL. Conclusion: The various histologic subtypes of PML have characteristic manifestations in the neck, chest, and abdomen, which allow their distinction on CT.