• Allo-HCT recipients undergoing a bronchoscopy at MDACC who consent to undergoing study airway brushings in addition to clinically indicated bronchoscopic procedures (e.g. bronchoalveolar lavage)

‣ 5 patients with advanced BOS - forced expiratory volume in one second (FEV1) =\< 75% predicted and meeting other National Institutes of Health (NIH) criteria (FEV1/forced vital capacity \[FVC\] ratio 0.7, presence of air trapping or graft versus host disease \[GVHD\] of another organ)

⁃ 5 patient with early BOS - at least 10% decline in FEV1 from baseline values, with FEV1 \>= 75% predicted, and 1 high-risk feature:

• Active systemic chronic GVHD with new early airflow obstruction OR

∙ Respiratory viral infection in last three months with resolution of viral symptoms but new airflow obstruction

⁃ 3 patients with no pulmonary impairment (FEV1 within 5% of baseline values)

• Lung allograft recipients undergoing a bronchoscopy at Houston Methodist who consent to undergoing study airway brushing sin addition to clinically indicated bronchoscopy procedures

‣ 5 patients with BOS Stage 2 or higher (\>= 35% decline in FEV1 from baseline values)

⁃ 5 patient with BOS Stage 0p or 1 (10-35% decline in FEV1 from baseline values)

⁃ 3 patients undergoing screening bronchoscopy without decline in FEV1

⁃ patients with undiagnosed lung cancer and chronic obstructive pulmonary disease diagnosed by pulmonary function testing (FEV1/FVC less than the lower limit of normal with \>20 pack-year history of smoking)