Spontaneous Pneumothorax as an Initial Manifestation of Metastatic Papillary Thyroid Carcinoma

Spontaneous pneumothorax occurs in a variety of lung diseases. Primary or metastatic lung cancers are rare, but important causes of pneumothorax. We report here on a case of pulmonary metastasis of thyroid papillary carcinoma that initially presented as spontaneous pneumothorax. A 32-year-old male with no history of thyroid disease underwent wedge resection of the lung due to recurrent pneumothorax. Histologically, the pleura and subpleural lung parenchyma revealed several micronodular lesions and randomly scattered glandular structures with mild cytological atypia. The cells were characterized by their overlapped hypochromatic nuclei with longitudinal grooves and inconspicuous nucleoli. On the additional sections, we found a few intranuclear inclusions and colloid-like material in the follicular structures. The glandular cells were immunoreactive for thyroglobulin, TTF-1, CK 7 and HMW-CK and they were focally immunoreactive for EMA, but they were negative for S100, chromogranin and CEA. The Ki-67 labelling index was 4%. Neck ultrasonography revealed an ill-defined hypoechoic nodule in the left lobe of the thyroid. The diagnosis of conventional, classical papillary carcinoma was made by both the cytology and the total thyroidectomy specimen. Pathologists should conduct a through histologic examination for the patients with recurrent spontaneous pneumothorax to search for the underlying causes.