An 8-year-old girl presented to our hospital with painful swelling of the left thigh and soft-tissue swelling in the right chest wall. The patient’s history revealed that the swelling had been present since birth but had grown slowly. She had no history of relevant trauma. Her blood pressure was 145/95 mmHg (normal value, <115/76 mmHg), and her heart rate was 105 beats per minute (normal value, 75–118 beats per minute). The patient’s electrocardiogram displayed sinus tachycardia. Physical examination revealed soft-tissue hypertrophy in the left thigh and right lower chest wall. A painful soft and flexible mass measuring approximately 5 × 6 × 15 cm (in the anteroposterior, transverse, and craniocaudal directions, respectively) was detected at the left thigh. Moreover, a painless soft mass measuring approximately 3 × 8 × 10 cm (in the anteroposterior, transverse, and craniocaudal directions, respectively) was detected in the right lower chest wall, and the overlying skin was intact. Pink macules with a 3-cm diameter on the anterior left superior thigh and a 2.5-cm diameter in the left inguinal region were detected. Examination of other systems, including the cardiovascular system, revealed normal findings. Laboratory test results were within normal limits. Abdominal US showed perirenal vascular collaterals, and musculoskeletal US of the left thigh revealed vascular collaterals (images not shown). Therefore, thoracoabdominal CT angiography (Fig 1a–1c) and contrast material–enhanced MRI of the bilateral thigh (Fig 2a–2c) were performed.Thoracoabdominal CT angiography with sagittal reconstruction showed a fatty right chest wall mass without any cystic or solid component representing fatty tissue overgrowth and extensive abdominal and left paravertebral varicose vascular structures (Fig 1a). Thoracoabdominal CT angiography with coronal reconstruction revealed hypoplasia in the left kidney, thoracoabdominal scoliosis, and fatty infiltration in the left psoas muscle (Fig 1b). Axial abdominal CT angiography (Fig 1c) showed fatty infiltration and reduction in muscle mass in the left psoas, quadratus lumborum, multifidus, and erector spinae muscles and extensive vascular malformations. Moreover, CT shows paravertebral vascular collaterals are associated with dural veins. Axial T1-weighted MRI of the bilateral thigh (Fig 2a) revealed fatty replacement of the left quadriceps femoris muscle, including vascular malformations, and disrupted the normal fibrillary pattern of striated muscle. Coronal T1-weighted unenhanced MRI of the bilateral thigh (Fig 2b) revealed fatty replacement and disrupted the normal fibrillary pattern of the left quadriceps femoris muscle and vascular collaterals extending to the left groin. Axial fatsaturated contrast-enhanced T1-weighted MRI (Fig 2c) revealed enhancing low-flow vascular malformations in the left thigh. Time-resolved MR angiography was performed to screen for a high-flow component, and there was no high-flow vascular component in the left thigh. However, there was a high-flow vascular component in the pelvis (not shown). Excisional muscle biopsy was performed from the left thigh. In the cross-sectional macroscopic examination of the specimen, the dense fibrofatty tissue consisted of a variable mixture of vascular clusters and thin-walled blood-filled venous channels that separate skeletal muscle bundles. Abnormal lymphatic vascular components also were present. Genetic analysis of tissue biopsy revealed the PIK3CA gene mutation, and Sanger sequencing revealed the mutant allele frequency was 27.8%. The diagnosis of PIK3CA-related overgrowth spectrum (PROS) was suggested according to clinical, radiologic, and pathologic findings. Because of the congenital truncal lipomatous overgrowth, vascular malformations, epidermal nevi, scoliosis (CLOVES), and left renal hypoplasia, a diagnosis of CLOVES syndrome was made. Moreover, the diagnosis of the fibroadipose vascular anomaly (FAVA) was made according to clinical, radiologic, and pathologic analysis findings comprising fibrofatty infiltration of muscle and atrophy of the affected muscles, unusual lymphatic and venous dilatations (phlebectasia) with pain, and lipomatous overgrowth of the affected extremity. What is your diagnosis?