The process seen here is representative of post-transplant lymphoproliferative disorder (PTLD), which is caused by Epstein-Barr virus infection that infects B lymphocytes. A proliferation of B lymphocytes is normally controlled by T lymphocytes, but immunosuppressed persons following transplantation have reduced T cell function and subsequent uncontrolled B cell proliferation. This B cell proliferation ranges from benign lymphoid hyperplasia, polymorphous or monomorphous proliferation, and non-Hodgkin lymphoma. PTLD can occur in 1 to 10% of organ transplant recipients, depending on the organ transplanted, the recipient’s age, and the immunosuppressive regimen. PTLD can involve multple organs, most commonly the tonsils, cervical lymph nodes, gastrointestinal tract, and lungs.
The process shown here could also represent intravascular lymphomatosis with an intraluminal proliferation of large mononuclear lymphoid cells in small pulmonary arteries, veins and alveolar capillaries. Most cases are of B cell origin. Most frequently involve the CNS and skin. Primary pulmonary intravascular lymphomatosis is extremely rare, though at autopsy most cases of intravascular lymphomatosis have pulmonary involvement. Most cases occur in older patients. The typical signs and symptoms include dyspnea, cough, and fever. Chest X-ray and CT scans show reticulonodular infiltrates. Pulmonary function tests show decreased diffusing capacity from vascular obstruction by the neoplastic cells. Excluding one case showing pulmonary hypertension, the clinical features suggested interstitial lung disease and required open lung biopsy for diagnosis.