A Case of Paraneoplastic Cushing’s Syndrome in Recurrent Squamous Cell Carcinoma

Abstract

Abstract Background: Ectopic production of ACTH causing Cushing’s syndrome (CS) is rare but has been well described in association with bronchial carcinoids, thymomas, pancreatic malignancies, and small cell lung carcinomas. We report a rare case of CS caused by ACTH-producing non-small cell carcinoma. Clinical Case: A 71 year-old man with a history of squamous cell carcinoma of the lung (T2bN1M0) 10 years prior who underwent lobectomy and adjunctive chemotherapy, presented with a new cough, weight loss, and bilateral lower extremity edema. He was also noted to have significant fatigue, hypertension, symptomatic hyperglycemia, and hypokalemia. CT chest revealed a large right perihilar mass with mediastinal adenopathy and numerous hepatic lesions. A biopsy of the liver lesions revealed a poorly differentiated carcinoma with neuroendocrine features strongly positive for AE1/3 with focal p40+, CK7, synaptophysin, chromogranin, and TTF1. It was negative for p63, CK5/6, CDX2, CK20, and GATA3. The morphology and immunohistochemical staining favored a squamous primary. Unfortunately, there was insufficient tissue sample to stain for ACTH. Biochemical evaluation revealed: post-1 mg dexamethasone serum cortisol 74.8 µg/dL (N < 1.8 µg/dL), 24 hr urine free cortisol 2987 µg/g creatinine (normal: < 32 µg/g creatinine), and ACTH 170 pg/mL (N < 47 pg/mL). Other notable findings at presentation were potassium 2.8 mmol/L (N: 3.7-5.1 mmol/L) and glucose 371 mg/dL (N: 74-99 mg/dL). MRI brain revealed focal pituitary infundibular thickening up to 6 mm in diameter and an enlargement of the pituitary gland concerning for metastasis. The patient’s clinical course was complicated by persistent hypokalemia and hyperglycemia which were treated with spironolactone 100 mg twice a day and insulin therapy, respectively. Ketoconazole 100 mg twice a day was initiated for the hypercortisolemia; etoposide, carboplatin, and atezolizumab were started for the neuroendocrine tumor. The patient expired due to sepsis one month after the diagnosis of Cushing’s syndrome. Conclusion: We report a rare case of paraneoplastic Cushing’s syndrome due to poorly differentiated neuroendocrine tumor with a squamous cell carcinoma primary. ACTH producing non-small cell carcinomas have been seldom reported in the literature. Although we were unable to provide ACTH staining on pathology, the existence of an obvious neuroendocrine tumor, marked elevation in ACTH, and an MRI which was negative for a pituitary adenoma, strongly suggests paraneoplastic Cushing’s syndrome.