CASE A 79-year-old Hispanic man with a greater than 30-pack year smoking history presents to the pulmonary clinic for evaluation
of a right upper lobe (RUL) lung nodule. The patient reports minimal dyspnea on exertion for the last 2 years and no other
complaints.
What's your diagnosis? (IMAGE: GILDA DIAZ-FUENTES, MD)
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The physical exam was unremarkable. Pulmonary function test results are consistent with mild obstructive airway disease. Chest
radiography demonstrates RUL haziness, and chest CT reveals an apparent nodule in the RUL (see the CT scan). Positron emission
tomography (PET) demonstrates no uptake in the nodule.
Given the high likelihood for malignancy, surgery is recommended, but the patient is reluctant to undergo surgery in light
of the negative PET scan. Further consultation and review of the initial CT findings with the surgeon and radiologist yield
the suspicion that the nodule is a bony structure. A second chest CT scan is obtained.
- What is the likely diagnosis?
- What is the next step in management?
COMMENT Both CT scans demonstrated a RUL pseudonodule caused by a hypertrophic first costochondral junction. Pseudonodules are round
or oval opacities identified on lung window CT surrounded by aerated lung that typically originate from the first or second
costochondral junctions or the sternoclavicular junction. These entities can mimic intrapulmonary lesions on frontal radiographs.
Costal cartilage ossification is frequently seen, with the first costal cartilage calcified more often and more extensively
than the others. The inferior portion of the hypertrophic costochondral junction is surrounded by lung. CT through the inferior
aspect of the costochondral junction produces a pseudonodule which is due to partial volume averaging as occurred in our patient.
CT images obtained 7 to 10 mm cephalad demonstrate the costochondral junction, which should be vertically aligned with the
pseudonodule. Exuberant ossification of the costochondral junction can hide significant pathology posterior to the junction.
Pseudonodules can be caused by ECG pads or other devices on the patient's skin as well as percutaneous lesions that protrude
from beneath the skin. Other lesions that may mimic a nodule include sclerotic bone lesions, such as bone islands, healing
rib fractures, and spinal osteophytes. Likewise, mediastinal and pleural lesions that are pedunculated and project into the
lung can appear as nodules when viewed from the front.
Pseudonodules due to ossification of the costochondral junction are not uncommon, and they are likely to be seen more often
as our population ages. To avoid unnecessary studies and surgical intervention, clinicians should be aware of this common
condition and avoid misinterpreting findings and diagnosing a lung pseudonodule as a true pulmonary nodule.
The patient was informed of the benign findings. Chest films were repeated at 6 months and demonstrated no changes. He agreed
to participate in a smoking cessation program and is doing well.
Contributed by LAKSHMI VARADARAJALU, MD, SATISH KHANEJA, MD, ERNESTO SY, MD, and GILDA DIAZ-FUENTES, MD, Bronx-Lebanon Hospital Center, Bronx, NY.
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