Leukemic infiltration of the lung following allogeneic hematopoietic stem cell transplantation

Pulmonary leukemic infiltration (PLI) is more common than generally recognized, but accurate antemortem diagnosis with pathological proof is rarely achieved. We describe herein the clinical courses of two patients with PLI following hematopoietic stem cell transplantation (HSCT). One case is a male patient with acute biphenotypic leukemia, and the other is a female patient with myelodysplastic syndrome. In both cases, hyperleukocytosis did not proceed to PLI. Moreover, the former case presented PLI as the initial manifestation of relapsed leukemia and the latter was accompanied with the fungal pneumonia. High-resolution computed tomography (HRCT) of the chest at onset of PLI showed diffuse small nodular lesions along peribronchovascular bundle, and diagnosis of leukemic infiltration was made based on pathological findings obtained from transbronchial lung biopsy. Biopsy specimens further revealed leukemic infiltration along the lymphatic surrounding the peribronchial or perivascluar regions, which corresponded well with HRCT findings. Thus, radiological and pathological corroborating assessment was important to reach the correct diagnosis.