Title : The role of EBUS TBNA (endobronchial ultrasound transbronchial needle aspiration) in the diagnosis of small cell lung carcinoma (SCLC) secreting ectopic ACTH (adrenocorticotropic hormone)
Introduction: SCLC (Small cell lung carcinoma) is the most common cancer associated with paraneoplastic syndromes. In many cases of suspected ectopic secretion of ACTH (adrenocorticotropic hormone), it is difficult to confirm the diagnosis histologically or cytochemically, especially when the tumor is located in the mediastinum
Case presentation: We report a case of 50-year-old male patient presenting with a mediastinal SCLC with clinical and biochemical characteristics suggestive of ectopic secretion of ACTH. Patient initially presented with severe hypertension, severe and persistent hypokalemia resistant to standard treatment, metabolic alkalosis, new-onset diabetes mellitus and altered mental status as the first clinical manifestations of ectopic ACTH-secretion. Computed tomographic scan of the thorax revealed left mediastinal mass within the aortopulmonary window with signs of vascular invasion, enlargement of the mediastinal lymph nodes in 4L, 10L and ipsilateral small pleural effusion (figure 1). The diagnosis of SCLC was made with EBUS-TBNA biopsy of the mediastinal tumor. Histologic analysis of the samples confirmed the diagnosis of small cell lung carcinoma and immunocytochemical staining of the samples confirmed the secretion of ACTH by tumor cells (figure 2 and 3). The patient was treated with combination of spironolactone and ketoconazole to decrease levels of ectopic ACTH prior to chemotherapy
Conclusion: The diagnosis of the source of ectopic secretion of ACTH can be very difficult when the tumor is located in mediastinum. EBUS-TBNA is an effective, safe and accurate tool for diagnosing mediastinal tumors and providing sufficient tissue samples for histological and immunocytochemical analysis.