A Case of Myxoid Adrenocortical Neoplasm: Computed Tomography and Magnetic Resonance Imaging Characteristics
A 70-year-old man was found to have an adrenal mass on non-enhanced computed tomography (CT) scanning, performed as part of a detailed examination for liver dysfunction by the attending physician. He was referred to our hospital for further examination and treatment. Examination on admission revealed that the patient was moderately overweight (weight, 71.5 kg; height, 167.8 cm; BMI, 25.6) and hypertensive (133/75 mmHg); hypertension was treated with nifedipine. Laboratory findings were within normal ranges except for γ-guanosine triphosphate, which was 51 IU/L (normal range 10-47 IU/L). He also underwent endocrine evaluation, which showed no functional abnormalities. CT scanning demonstrated a solid, homogeneous mass (24×38×34 mm) with well-defined edges in the left adrenal gland. Attenuation measurements were 22 Hounsfield units (HU) on the precontrast image, 111 HU on the arterial phase image, and 29 HU on the delayed phase image (). Magnetic resonance imaging (MRI) showed no loss of signal intensity in T1-weighted out-of-phase images but high signal intensity on T2-weighted and diffusionweighted images (DWI) (). A temporal enhancement effect was seen on dynamic MRI. Left open adrenalectomy was performed.\nThe mass was macroscopically visualized as a well-circumscribed, golden yellow tumor (), histologically characterized by an incomplete capsule and focally infiltrative margin. The tumor cells were arranged in glandlike structures and the background of the tumor was myxoid. In some areas, a trabecular pattern was also recognized. Tumor cells contained scant cytoplasm, although clear cells with relatively abundant cytoplasm were focally observed (, ). Hematoxylin and Eosin staining revealed that tumor cells were present outside the capsule and had infiltrated the fatty tissue without disruption of the reticulin network (, ). Mitotic figures were rare (<1/20 under high-power field). Tumor cells immunohistochemically stained positive for melan-A, α-inhibin, synaptophysin, and vimentin, and negative for p53; the MIB-1 index was 2%. The tumor fulfilled 2 of the Weiss criteria (paucity of clear cells, high nuclear grade only focally) (). Hough score and van Slooten index were 1.21 (diffuse growth pattern, pleomorphism) and 7.4 (regressive changes, structural changes, nucleoli), respectively. Mitotane was not used as an adjuvant therapy. Neither recurrence nor metastasis was detected during the 10 months of follow-up. Long-term follow-up with imaging and adrenocortical hormonal measurement was implemented because two cases of recurrence have previously been reported.