Adenocarcinomas of unknown primary (ACUP) of the mediastinum mimicking lymphoma: CT findings at diagnosis and follow-up

ObjectiveTo describe the computed tomography (CT) features at diagnosis and after treatment of adenocarcinoma of unknown primary (ACUP) mimicking lymphoma of the mediastinum.MethodsFifteen patients with pathologically proven ACUP and with primarily mediastinal involvement were initially referred to the Hematologic Department of our institution with a suspected diagnosis of lymphoma, and accounted for our study population. Presenting symptoms and baseline biological values were analyzed. All thoraco-abdominal CT studies were reviewed for the location and size of the mediastinal involvement and associated findings. Follow-up chest CT was performed in 14 patients after radiotherapy, chemotherapy or surgical treatment.ResultsThe most frequent CT feature was a large anterior and middle mediastinal mass (67%), with no calcification. Associated findings included the presence of lung nodules (40%), compression of large mediastinal vessels (33%) and pleural effusion (27%). Follow-up CT, performed in 14 cases, suggested partial or complete responses in 7 patients (50%) 4 weeks after the treatment onset.ConclusionsMediastinal ACUP is a differential diagnosis of large mediastinal masses and is frequently associated with lung nodules and mediastinal vascular compression.