Intrapulmonary lymph nodes masquerading as pleural metastasi
The differentiation between pleural dissemination and intrapulmonary lymph nodes is important if pleural nodules are present in a patient with lung cancer. It is imperative to make comparisons with previous images whenever possible, and surgery should be performed for accurate staging unless obvious distant metastases are observed.

A 71-year-old man with a 50 pack-year history of smoking presented with an abnormal shadow on chest radiography. Chest computed tomography (CT) revealed a 45-mm-sized lesion in the right lower pulmonary lobe and two pleural nodules. Transbronchial biopsy revealed squamous cell carcinoma. Single-slice chest CT performed 13 years ago revealed a very small pleural nodule. Thoracoscopy revealed a black nodule in the pleura, and histopathological examination revealed that the two pleural nodules were intrapulmonary lymph nodes (IPLNs).

The present case described herein provides two important clinical suggestions. First, IPLNs can grow without malignant findings. A previous study of 794 IPLNs revealed that 123 (15.5%) grew slowly and 66 (8.3%) enlarged like malignant nodule, suggesting the possibility of growing IPLNs.1

Second, comparisons with previous imaging examinations are useful, even if they are of comparatively poor quality. The presence of one pleural nodule and absence of lung cancer on CT images obtained more than 10 years ago led us to consider the possibility of IPLNs and proceed with surgery. Furthermore, linear densities extending from the nodules, pathologically ectatic lymphoid channels and a characteristic of IPLNs, were seen in this patient.