A 55-year-old gentleman was referred to surgeons for screening colonoscopy in view of family history of bowel cancer. His mother, maternal aunt and two cousins had history of bowel cancer. When seen by the surgeons, he gave 4-month history of intermittent abdominal bloating and rectal bleeding. His past medical history included a recent diagnosis of hypertension, a chronic history of facial neuralgia and history of excision of numerous facial skin tags. He was on amlodipine 5 mg daily and Sumatriptan.
On examination he had, high blood pressure, subcutaneous lumps on both thighs and accessory skin tags. His routine blood investigations were unremarkable and he underwent a colonoscopy, which revealed a pedunculated splenic flexure lesion which could not be resected endocsopically. He subsequently underwent a laparoscopic descending colon colectomy. As part of the work up, he had a CT Scan of abdomen prior to surgery, which revealed an incidental 3.4 cm right adrenal lesion for which he was referred to endocrinologist. He had inadequately suppressed cortisol level after an overnight dexamethasone test and after a standard low dose dexamethasone test with an unsuppressed ACTH done at baseline. The 24 h urinary catecholamines and aldosterone/renin ratio were normal. The histopathology report from colon had appearances of a submucosal neurofibroma suggestive of gastro intestinal stromal tumour (GIST).
We present a case of large intestine neurofibroma and subclinical Cushings syndrome from a functional adrenal adenoma with a likely diagnosis of neurofibromatosis 1 (NF-1).
GISTs have been reported to occasionally occur in patients with NF-1. NF-1 gene is a tumour suppressor gene and recent studies have demonstrated loss of neurofibromin in tumours from NF 1and non- NF-1 patients. The co-existence of GIST and a neuroendocrine tumour (functional adrenal adenoma) is a rare one and question arises if this is due to tumour predisposition or coincidence.