Pituitary oncocytoma presenting as Cushing's disease
A 19-year-old girl presented with complaints of weight gain, hypertrichosis, menstrual irregularities of 2 years and hypertension of 4 months duration. She also gave history of easy bruisability, broad voilaceous striae over abdomen and thighs, recurrent vaginal candidiasis. Her height was 154 cm, weight 77 kg, BMI of 32 kg/m2, and waist hip ratio 0.95 on examination. She was normotensive on antihypertensive medications. There was thinning of scalp hairs, mooning of face, facial plethora, hypertrichosis over face, increased supraclavicular and dorsocervical fat pad thickness, voilaceous abdominal striae, thinning of skin over dorsum of hands, and proximal muscle weakness. There was no neurological deficit including visual fields. OGTT detected IFG (fasting plasma glucose 102 mg/dl) and IGT (postglucose load 156 mg/ dl). Her bone mineral density estimation by DXA revealed osteopenia. Her hormonal evaluation revealed normal basal ACTH levels (38.7 pg/ml) in the presence of basal cortisol levels of 21.3 μg/dl (8 am) and evening cortisol of 23 μg/ dl (4 pm). Serum cortisol levels remained unsuppressed following overnight (18.6 μg/dl) and low dose (15.7 μg/dl) dexamethasone suppression test. However, it decreased by 73% on high dose dexamethasone suppression test (5.8 μg/ dl). MRI brain did not reveal any pituitary abnormality. Since neurosurgeons were reluctant to operate without localization and also to find source of ACTH, bilateral inferior petrosal sinus sampling (BIPSS) was planned with vasopressin stimulation due to nonavailability of CRH and desmopressin. The central to peripheral ACTH ratio on the right side was 28/1 and 32/1 in basal and postvasopressin respectively (normal <2 and <3 respectively). The interpetrosal sinus gradient was also significant (right IPS/left IPS = 13; normal <1.5) suggesting pituitary microadenoma on the right side of adenohypophysis. The patient was diagnosed as having Cushing's disease caused by an ACTH-secreting pituitary adenoma, which was extirpated (adenomectomy) by transphenoidal surgery. The sixth postoperative day basal Cortisol level was 0.33 μg/dl, suggestive of possible remission of disease. She was discharged on replacement doses of hydrocortisone with advice on stress dosing and she is planned for gradual tapering of hydrocortisone doses.\nHistopathological examination on light microscopy showed more than 95% of cells arranged in a large sheet of polyhedral cells with eccentric nuclei and moderate amount of bright eosinophilic, granular cytoplasm consistent with oncocytes, which confirmed the diagnosis of oncocytoma []. These cells were arranged in diffuse, solid, and sinusoidal pattern []. These cells were strongly positive for ACTH []; prolactin; GH; S100; neuron specific enolase; chromatogranin A; and synaptophysin on immunohistochemical staining and displayed a bright brown positivity universally. Phosphotungstic acid hematoxylin (PTAH) staining revealed dark blue oncocytic cytoplasm [].