Adenosquamous carcinoma of the lung diagnosed by cytology?: a diagnostic dilemma

Adenosquamous cell carcinomas of the lung are rare tumours and are associated with a poor prognosis compared to other non-small cell carcinomas. We report a case of a solitary lung carcinoma evaluated by bronchial brush and lavage cytology, bronchial biopsy and pleural fluid cytology. Cytological assessment of the pleural fluid demonstrated non-small cell carcinoma and immunohistochemical staining confirmed a metastatic lung adenocarcinoma. The bronchial brush and lavage specimens, however, demonstrated the cytomorphological features of squamous cell carcinoma, which was confirmed by the bronchial biopsy. The finding of a mixed squamous and glandular component predicts a poor prognosis for this patient. The identification of a squamous component with the non-small cell carcinoma is important as this excludes the patient from anti-VEGF monoclonal antibody treatment due to the increased risk of haemorrhage.