MICROSCOPIC DESCRIPTION: The core biopsy contains lymphoid proliferation. There are scattered atypical lymphoid cells forming sheets and nodules, surrounded by fibrous tissue. The atypical lymphocytes are large in size. They have enlarged clefted and hyperchromatic nuclei, prominent nucleoli and scanty cytoplasm. The background contains small mature lymphocytes and histiocytes. No granulomas are noted. The tumour cells are CD20, CD30 (weak, focal), CD45, PAX-5, OCT-2, BOB-1, bcl-2 (focal), bcl-6 (focal), p53 and MUM1 positive. The Ki-67 index is about 95% (counting only the large cells). c-Myc stains about 30% of the large cells. They are CD3, CD10, CD15, TdT, ALK-1 and EBER-CISH negative. The features are those of diffuse large B-cell lymphoma, with activated B-cell-like phenotype. It is not possible to determine whether this is primary mediastinal large B-cell lymphoma or from systemic lymphoma on histology and immune profile alone.
DIAGNOSIS: Anterior mediastinal mass biopsy: Diffuse large B-cell lymphoma.
Report courtesy of the Royal Melbourne Hospital radiology department.