The diagnosis of primary mediastinal lymphoma is primarily based on biopsy findings, followed by immunophenotype and surfae markers.

Biopsy is the diagnostic study of choice.

• The diagnosis of primary mediastinal large B cell lymphoma relies on the exclusion of adequate tissue, which offers most difficulty due to the location of the tumor, therefore an excisional biopsy is usually not possible.
• Therefore, surgical biopsy is highly preferred.^[1]
• Due to fibrosis, needle aspirates are often paucicellular and fail to provide information about the tissue.
• Small biopsies may be non-diagnostic because the lesion is not sampled adequately or because crush artifact or extensive necrosis, fibrosis, or cystic change obscures the diagnostic lesion.
• Similarly, core biopsies mostly contain fibrotic tissue or tumor cells that are disrupted and not useful.
• To obtain sufficient tissue for biopsy , patients usually undergo either one of the following techniques:^[1]
  • Cervical mediastinoscopy
  • Anterior mediastinotomy
  • Thoracoscopy