Intralobar pulmonary sequestration associated with marked elevation of serum carbohydrate antigen 19-9

This report describes a 62-year-old man who experienced elevated serum carbohydrate antigen 19-9 (CA19-9) levels (>500 U/mL) for 4 years, and was finally diagnosed with right intralobar pulmonary sequestration. Surgery confirmed the presence an aberrant artery arising from the descending thoracic aorta and entering the right lower lobe basal segment. Immunohistochemistry demonstrated markedly positive staining of CA19-9 in the ciliated cylindrical epithelia, alveoli, and mucus in the cysts. After pulmonary resection, CA19-9 levels decreased to within a normal range. Therefore, the cause of the elevated serum CA19-9 levels in this case was almost certainly due to intralobar pulmonary sequestration.