A 23-year-old woman presented with gradual-onset left chest and back pain. She had at medical history of asthma. She was a never smoker with no significant family history. Her observations and examination were normal. Blood tests performed revealed a raised C reactive protein of 119 mg/L and high white cell count of 12.81×109/L. A chest radiograph showed left hilar consolidation (figure 1A). She was treated with oral clarithromycin and follow-up radiograph showed resolution of the consolidation (figure 1B).

(A) Chest radiograph at presentation showing left hilar consolidation. (B) Chest radiograph showing resolution of left hilar consolidation. (C) CT thorax showing left-sided complex pleural effusion with large bore chest drain in situ and 2.6 cm fluid collection in left hemithorax with surrounding consolidation. (D) Persistent fluid filled density in the left anterior hemithorax with resolution of the surrounding pleural effusion. (E) Postoperative follow-up chest radiograph showing elevated left hemidiaphragm.

One year later, she represented with a 10-day history of dry cough and pleuritic chest pain. A chest radiograph demonstrated a left-sided pleural effusion and blood tests were in keeping with infection. Pleural fluid examination showed an exudative effusion by Light’s criteria (pleural fluid protein 55.8g/L, Lactate dehydrogenase (LDH) 1798U/L, glucose 3.74 mmol/L, serum protein 77 g/L, serum LDH and pleural fluid pH not available) and mixed inflammatory cells on cytology and negative culture. CT thorax postdrainage demonstrated a persistent large, complex loculated effusion with pleural thickening, consolidation and a suspected intraparenchymal collection in the left upper lobe (figure 1C). A large bore chest drain was inserted and her condition improved with a prolonged course of antibiotics.

One month later, she had a recurrence of her symptoms and underwent a video-assisted thoracoscopy for surgical debridement and washout of her pleural cavity. No focal collection was identified intraoperatively. A 6 cm ‘abscess’ was noted at the lingula, it was not suitable for anatomic resection so was punctured and biopsies sent for microbiology and pathology. No pus or colloid material was found. Bronchoscopy performed at the same time revealed extrinsic compression of the left upper lobe bronchus. She was discharged again on a prolonged course of antibiotics.

After cessation of oral antibiotics her symptoms returned and repeat ultrasound demonstrated a 4.9 cm posterior collection. Repeat CT thorax showed resolution of the pleural effusion but a persistent presumed ‘lung abscess’ (figure 1D). She underwent a left thoracotomy upper trisegmentectomy and histology confirmed a 50 mm left upper lobe mature cystic teratoma (figure 2).

(A) Macroscopic appearances of resected intrapulmonary cystic teratoma. (B) Macroscopic appearances of resected intrapulmonary cystic teratoma (bisected). (C) A digital photomicrograph of a H&E-stained large section, showing a mature teratoma in the centre of the image, non-involuted thymic tissue on the right side of the image and inflamed fibrotic lung tissue down the left side edge. The teratoma tissue in this section includes cystic spaces lined by stratified squamous epithelium, salivary gland-like lobules, adipose tissue and cartilage.

Three months after the operation, the patient was symptom free and a chest radiograph showed a raised left hemidiaphragm and resolution of the consolidation and effusion (figure 1E), with no further requirements for antibiotics.

Intrapulmonary cystic teratoma is a rare entity and is usually a benign tumour affecting a young adult population, with no gender preference.1 Malignant transformation has been reported in 1%–2% of cases of gonadal germ cell tumours.2

Extragonadal germ cell tumours are rare with only 3% of germ cell tumours being located outside the gonads. The majority are mature cystic teratomas being most commonly seen in the ovary.3 Teratomas can be composed of tissue from all three germ layers (ectoderm, mesoderm and endoderm). Teratomas of the lung are derived from the third endodermal pouch during formation of the thymus in early embryogenesis.3

Intrapulmonary teratomas are frequently misdiagnosed as aspergilloma, tuberculosis or neoplasm and there is often a delay from presentation to diagnosis.4 Hallmark features such as trichoptysis (expectoration of hair) are reported but are late features as they represent teratoma rupture into the endobronchial tree.5

Without surgical resection complications can arise secondary to local invasion and pressure effects such as massive haemoptysis, local collapse, acute respiratory distress syndrome secondary to tumour rupture into the pleural space or postobstructive pneumonia and bronchiectasis. Complete surgical resection is an effective treatment with excellent prognosis.

In our patient, the teratoma is likely to have caused recurrent postobstructive infection leading to a complicated parapneumonic effusion. A differential for the presumed abscess was considered at the time however no specific radiological features of teratoma were present. Typically, cystic teratomas appear as fat-containing masses on CT scan with dependent elements made up of areas of greater density representing a combination of fat, hair, debris and fluid.6 Dermoid plugs may also be present containing calcification (teeth/bone) and are represented by rounded masses extending into the cyst from the cavity wall.6

Non-resolution of the intrapulmonary cavitating mass led to the decision for resection where the diagnosis of benign intrapulmonary cystic teratoma was confirmed.

Consent obtained directly from patient(s).