Findings necessary for diagnosis, always present

(1) Mixed mononuclear cell infiltrate containing

large and small lymphoid cells, often along

with plasma cells and histiocytes, which replaces

the lung parenchyma and shows vascular

infiltration.

(2) Variable numbers of CD20-positive large B cells,

often with atypia, present in a background of

CD3-positive small lymphocytes.

Supportive findings, usually but not always

present

(1) Necrosis of the cellular infiltrate.

(2) Positive ISH for EBER.

(3) Multiple lung nodules radiologically, or skin or

nervous system involvement.