Thoracic SMARCA4-deficient undifferentiated tumour: Diagnostic challenges and potential for misdiagnosis in small tissue samples.

We report a diagnostically challenging case of a SMARCA4-deficient undifferentiated tumour to emphasize its potential to mimic other malignant tumours on histology, especially in small biopsies and where rhabdoid morphology is lacking. A 48-year-old man, who was known for chronic obstructive pulmonary disease and polysubstance use, presented with dyspnoea and an anterior mediastinal mass that had grown rapidly over a seven-month period. The rapid growth and location in the anterior mediastinum raised clinical suspicion for lymphoma or a germ cell tumour. Microscopic examination of a transthoracic, ultrasound-guided, core needle biopsy revealed relatively uniform, malignant epithelioid cells with clear cytoplasm, but lacking any rhabdoid features. Tumour necrosis was prominent. The immunohistochemistry panel was negative for lymphoma markers, but positive for SALL4 (a marker typically associated with germ cell tumours), CD34, EMA, and HepPar1, while expression of SMARCA4 and claudin-4 was entirely lost. Only focal cytokeratin expression was demonstrated. SMARCB1 (INI1) expression was retained. The diagnosis of SMARCA4-DUT was made based on these findings. Unfortunately, the tumour was already at an advanced stage at diagnosis (stage IVA) and the patient had a poor performance status. He was treated with palliative radiotherapy with no significant improvement in performance status and passed away 3 months after diagnosis. The case highlights the importance of considering SMARCA4-DUT in the differential diagnosis of an undifferentiated, rapidly growing thoracic tumour and the potential for misdiagnosis on a small tissue sample, particularly as rhabdoid morphology may be absent.

Syncope due to tracheal adenoid cystic carcinoma.

We present a case of a 34-year-old male who presented with syncope secondary to a large adenoid cystic carcinoma (ACC) of the distal trachea. A computed tomography and flexible bronchoscopy showed almost complete occlusion of the distal trachea. Resection with curative intent was performed, but resection margins were unfortunately not clear. The patient was subsequently offered adjuvant radiotherapy. Tracheal tumours comprise a small proportion of respiratory tract neoplasm, accounting for only about 2% of airway malignancies. Squamous cell carcinoma is the most common tracheal tumour, followed by ACC. Symptoms are usually attributable to the intraluminal component of the tumour causing an obstruction of the airway, resulting in stridor, dyspnoea, wheezing, haemoptysis, and cough. Syncope as a presenting symptom is exceedingly rare.

Fatal tumour pulmonary embolism.

A 30-year-old female with no significant past medical history was referred to our facility with sudden onset of shortness of breath. She had a low clinical probability for pulmonary thromboembolism and a computed tomography angiogram showed enlarged pulmonary arteries but no in situ thrombi. She developed recurrent episodes of hypotension and hypoxia, and was transferred to the intensive care unit where she died despite active resuscitation. An autopsy revealed extensive lymphatic and pulmonary vascular tumour emboli as the immediate cause of death. Pulmonary tumour embolism is a very rare cause of death, but can occur in patients who have an occult neoplasm.