Adrenal incidentaloma: A case report of Pheochromocytoma (PCC) with atypical radiological features

INTRODUCTION: Adrenal incidentaloma (AI) is an adrenal lesion ≥ 1 cm discovered accidentally during an imaging technique not aimed to assess the adrenal gland (1). Most AIs are benign and nonfunctioning, about 20% are functioning in form of hypercortisolism, hyperaldosteronism, pheochromocytoma (PCC) or sex steroid overproduction (2). Computed Tomography (CT) scan is vital in differentiating adenoma from non-adenoma. Triphasic CT adrenal protocol (TCTAP) with absolute percentage washout (APW) has good sensitivity and specificity in diagnosis of AI. Here we present a case of PCC with atypical CT features. CLINICAL CASE: A 45 years old male patient presented with abdominal pain, abdominal US revealed a right suprarenal mass of 55 mm and referred to endocrinologist for further management. During assessment, the patient had attacks of hypertension, no cushingoid features, BMI was 35 kg/m2 and his blood pressure 180/120 mmHg. Normetanephrine was very high (1016.9 pg/mL), cortisol (10.1 μg/dL), suppressible serum cortisol (1.7 μg/dL), normal DHEA-S (110 μg/dL) and ACTH was 13 pg/mL. Aldosterone, renin, aldosterone/renin ratio (ARR), Metanephrine, K+ are normal. TCTAP showed a homogenous 51×46 mm right adrenal mass of a native Hounsfield units (HU) of 25, portal phase HU of 86, delayed phase (at 15 minute) HU of 36 and APW was 81%, which are features consistent with lipid poor adenoma (LPA) rather than PCC or carcinoma. The patient referred to surgery, right adrenalectomy had been done after good preparation and the diagnosis of PCC had been confirmed by histopathological (HP) and immunohistochemical (IHC) staining. TCTAP used to differentiate adenomatous from non-adenomatous AI with good sensitivity and specificity (3). PCC is an uncommon with variable clinical presentation ranging from severe symptoms to very mild and even sometimes discovered incidentally as AI with about 1.5–14% of all cases of AIs (1). PCC has heterogeneous texture, variable sizes, native HU > 10, avid enhancement and slow washout (4). The present AI was homogenous, has a native HU of 25 and has avid enhancement at portal phase reaching to 86 HU, but the APW was 81% which is atypical for PCC, making lipid poor adenoma at the top list of differential diagnoses. Hormonal assessment revealed the diagnosis of PCC which was confirmed by histopathological (HP) and immunohistochemical (IHC) staining. An American study showed that two of eight PCCs have an APW > 60%, but both of these cases have native HU< 10 and the APW had been calculated at 10 minutes (5). Coincided with our patient and our protocol of 15-minute APW calculation, Yoon et al presented a case of PCC with native HU of 37, portal phase HU of 127 and delayed phase HU of 62 HU with APW of 72% (6). CONCLUSION: PCC is serious condition, could be asymptomatic and may be presented with a typical radiological feature, so biochemical and hormonal assessment is a cornerstone in management of AI. [Figure: see text]