Spontaneous hemothorax is a subcategory of hemothorax that involves the accumulation of blood within the pleural space in the absence of trauma or other causes (
2). Only a few reported cases of primary lung malignancy induced spontaneous hemothorax have been described (
3,
4). Lung cancer is a very rare cause of hemothorax, even in the setting of pleural extension (
1). Furthermore, bronchial carcinoid tumor-related spontaneous hemothorax has never been reported in the English literature to our knowledge, although there are reported cases of bronchial carcinoid associated spontaneous pneumothorax (
10,
11). Bronchial carcinoids belong to a broad spectrum of neuroendocrine tumors including typical carcinoid (TC) and atypical carcinoid (AC) tumors, large-cell neuroendocrine tumors and small-cell lung cancer (
12). TCs and ACs are low- and intermediate-grade, respectively (
12), and have similar gross pathologic and radiologic features that are largely dependent on tumor location. ACs are more aggressive than TCs (
13). Bronchial obstruction-related symptoms, such as recurrent obstructive pneumonitis/atelectasis and chest pain, are the most common symptoms of carcinoid tumors, followed by cough and hemoptysis with evidence of a bronchial obstructing lesion in the majority of patients (
13,
14). Pulmonary neoplasms associated with spontaneous pneumothorax sometimes cause spontaneous hemothorax due to torn adhesions. However, lung tumor-related spontaneous hemothorax without pneumothorax is extremely rare (
9). The mechanisms of tumor-related hemothorax without pneumothorax are explained as the compression and ischemic necrosis of pleural and pulmonary tissue, invasion of the pulmonary vessels by the tumor, or tumor rupture into the pleural cavity (
9).
A bronchial carcinoid tumor associated with hemothorax has never been reported, even though its hypervascular nature with hemoptysis is a common symptom (
13). Radiologically, a bronchial carcinoid tumor usually presents as a centrally located, well-defined hypervascular tumor with a typical iceberg sign (a small endobronchial portion and a large exobronchial portion) that appears on enhanced chest CT. These typical chest CT findings help in the imaging diagnosis of bronchial carcinoid tumors (
13). Although it has a hypervascular nature and commonly causes hemoptysis, we can assume that a centrally located tumor with well-defined margins, indicating a less invasive nature, would only rarely cause spontaneous hemothorax. Seldom do peripherally located carcinoid tumors present as solitary pulmonary nodules. Furthermore, ACs have certain features suggesting a more aggressive nature (
13). Therefore, a peripherally located AC has the potential to present a spontaneous hemothorax, not act as an obstructing symptom, as in our case.
The mechanism of AC-related spontaneous hemothorax was not determined in the present case through pathologic features including visible ischemic necrosis or pulmonary vascular invasion. However, observations of copious aggregation of red blood cells around the tumor margin abutting the visceral pleura on the pathologic specimen and high attenuation of the peripheral nodule on the unenhanced CT suggested intra-tumoral hemorrhage. Furthermore, the CT findings of the subfissural location of the tumor abutting the right major fissure, persistent loculated hemothorax along the right major fissure, and continuous low attenuation from visceral pleural space to the peripheral enhancing nodule suggest that the spontaneous hemothorax associated with peripheral AC in our case involved a rupture of this hypervascular tumor into the adjacent visceral pleural space.
These rare findings for bronchial carcinoid tumors make radiological diagnosis difficult. Furthermore, the adjacent loculated hemothorax along the right major fissure obscured the highly attenuated pulmonary tumor on the unenhanced CT images due to intratumoral hemorrhage, and enhanced surrounding atelectatic lung also obscured the hyper-enhanced pulmonary tumor on the enhanced CT images of the initial chest CT. However, on the follow-up chest CT scan after tube drainage of the hemothorax, a hypervascular SPN was clearly demonstrated in the peripheral lung of the right lower lobe. Therefore, a second-look chest CT after drainage of the hemothorax with improvement of atelectasis may facilitate imaging diagnosis of peripheral SPN as a cause of spontaneous hemothorax.
The prognosis for malignancy-associated hemothorax remains poor (
1). However, patients with bronchial carcinoid tumors have a high life expectancy. Lobectomy is the most common procedure for the treatment of bronchial carcinoid tumors due to their metastatic potential, regardless of their size or location (
12).
Our case highlights the possibility of delayed diagnosis of pulmonary neoplasm, especially when it has hypervascularity or is small in size and/or is found in a peripheral location, as a cause of spontaneous hemothorax due to the possible obscuration of SPN by hemothorax and/or atelectatic lung, as well as the tendency to overlook this rare condition.
In conclusion, lung cancer-related spontaneous hemothorax is a very rare disease entity. Furthermore, spontaneous hemothorax caused by the rupture of an atypical bronchial carcinoid tumor has never been reported in the literature. Therefore, a second-look chest CT scan after drainage of spontaneous hemothorax is mandatory, especially when there is no detectable cause of the spontaneous hemothorax found when examining the initial image, in order to consider peripheral small pulmonary neoplasm as a possible cause of spontaneous hemothorax. This strategy could improve prognosis of this rare condition through prompt and accurate diagnosis, and consequently optimize the surgical treatment of pulmonary neoplasm.
