A 43-year-old woman had a pulmonary tumor detected by a computed tomographic (CT) scan during follow-up for breast cancer 15 years previously. The tumor showed a solid mass measuring 42 × 32 × 12 mm in extensive contact with the pleura of the apex of the left upper lobe. The edge of the tumor was relatively well-defined with an irregular shape, and a bubblelike area was seen within it. The longitudinal slice high-resolution CT findings showed a flat and thick mass, and its inferior border was distinct and horizontal. The pathological findings by a thoracoscopic lung biopsy showed a localized pulmonary fibrosis of the apex, a so-called pulmonary apical cap (PAC). With the recent advances in CT scan technology, the detection of PACs is very likely to increase, and they must be differentiated from superior sulcus tumors.