Mediastinal teratoma presenting with hemoptysis and pleuritis misdiagnosed as tuberculosis (empyema)

Mediastinal teratoma is unusual in children. It is often difficult to diagnose because of its few early symptoms. Rarely, a cystic teratoma may rupture into adjacent structures, such as the pleural space, pericardium, lung parenchyma or tracheobronchial tree [1‐6], however tumor shape of the previous reported cases was more relatively typical than our present cases.

Here, we report a series of three children with recurrent hemoptysis and pleuritis attributed to mediastinal teratoma containing pancreatic tissue (all three patients) and calcification (patients 1 and 2). All these patients were initially suspected to have pneumonia, tuberculosis or empyema, and underwent relevant treatment, but without improvement. The main rarity of these cases was the dynamic imaging findings similar to the developmental process of tuberculosis in patients 1 and 2, the pachypleuritis in the patients 2 and 3, the extremely elevated inflammatory markers in serum and pleural effusion similar to empyema in patient 3, and the extremely atypical tumor shape on chest imaging in all patients especially in patient 2.

Mediastinal teratoma is mostly seen in young adults, and thymic teratoma is very rare regardless of age; however, patients 1 and 3 had definitive diagnosis of thymic teratoma. A teratoma is not easy to detect when small or not eroding other organs. Mediastinal teratoma with pulmonary and pleural involvement is rare, but the most common symptoms are dyspnea, continuous cough and chest pain [7, 8]. Hemoptysis is a very rare symptom of mediastinal teratoma, and is usually caused by recurrent infection due to lung compression or tumor rupture into the lung [3‐5]. In each of these cases, the teratoma had invaded adjacent tissue, especially the lung. In patients 2 and 3, the tumor had also invaded the pleural space, and had caused sudden dyspnea in patient 3. Patients 1 and 2 presented mainly with hemoptysis, but without obvious evidence of infection (especially in patient 1); patients 2 and 3 presented with chest pain.

The classic CT finding of mediastinal teratoma is a round or ovoid, cystic or cystic-solid mass with a clear, smooth outline. The density inside the teratoma is heterogeneous, like water, sebaceous fluid or soft tissue with or without calcified nodules [8]. In patient 1’s early clinical course, the small irregular teratoma lacked clear signs of extension into the lung tissue, and was mistaken for an enlarged hilar lymph node or pulmonary consolidation. However later did lung CT reveal calcification, cavitation and a low-density focus in the irregular mass. In patient 2, chest imaging initially revealed a large lobe consolidation in the right lung and right-sided pleuritis. Only subsequently was calcification identified in the right lower lobe and the thickened pleura, and irregular soft tissue in the right inferior mediastinum. However calcification, cavitation and pachypleuritis were the important features of tuberculosis. Therefore the clinical courses and dynamic imaging findings of patients 1 and 2 were similar to the developmental process of tuberculosis, and to the best of our knowledge there have been no previous reports of mediastinal teratoma presenting in these ways. Patient 3 initially presented with pulmonary consolidation and a massive pleural effusion. In the context of extremely elevated inflammatory markers in serum and pleural effusion, a diagnosis of empyema was reasonable. Even though the mass was only recognized later, it was still easily misdiagnosed as an encapsulated effusion or abscess that had not been completely absorbed. Therefore, mediastinal teratoma can be very difficult to diagnose.

In a few cases, calcification and cavitation are found in teratomas accompanied by lung erosion, resulting in a misdiagnosis of tuberculosis [3, 8], especially in developing countries with a high tuberculosis burden such as China. A case of mediastinal teratoma misdiagnosed as empyema in the early stages has also been reported before, and pleural effusion appeared to be purulent [9]. The tumor shape on chest imaging was extremely atypical in all our patients especially patient 2.

Pancreatic tissue has been identified within mediastinal teratomas before [10, 11]. Sommerlad et al. [6, 12] reported a fistula adjacent to the mediastinum secondary to non-purulent inflammation caused by digestive enzymes, however inflammatory markers were extremely high and the pleural effusion appeared to be turbid in patient 3, which increased the difficulty in diagnosis. It is presumed that pancreatic digestive enzymes are the main cause of tumor rupture and perforation of surrounding structures. In patients 1 and 2, hemoptysis was the chief complaint; the lung tissue adherent to the teratoma was partially eroded in patient 1, and severely eroded, necrotic in patient 2. These findings suggest that the hemoptysis was caused by erosion of small pulmonary vessels by digestive enzymes released by the teratoma. Only a few cases of teratoma rupture into the pleural space have been reported; in addition, these tumors may be associated with atelectasis, and post-obstructive pneumonia [13‐17]. Patient 2 presented with atelectasis and secondary collapse of the right lung. Patient 3 had a sudden-onset massive pleural effusion, suggesting that a teratoma rich in sebaceous fluid had ruptured into the pleural space; however, chest imaging at the time also suggested atelectasis or obstructive pneumonia. Pleural biopsies had been performed in patients 2 and 3; the fibrous tissue identified was suggestive of pachypleuritis. Although this was not recognized at the time, this was likely due to pancreatic tissue within the teratoma eroding surrounding structures and causing chronic non-purulent pleural inflammation.

Surgical resection is the only effective way to treat teratoma, especially for mature tumors. All our patients have remained well during follow-up.

We describe 3 rare cases of mediastinal teratoma misdiagnosed as tuberculosis or empyema. Mediastinal teratoma should be considered as a differential diagnosis in patients with hemoptysis, lung lesions and pleuritis of unknown origin. Calcification and pachypleuritis on chest imaging especially in patients without fever should be highly suspected of mediastinal teratoma. Pleural biopsy sometimes fails to assist in making a definitive diagnosis. Prompt recognition, diagnosis and treatment may reverse not only lung damage, but may prevent other complications.