An atypical imaging characteristic of calvarial metastasis of neuroblastoma as multiple multi-loculated cystic masses with internal blood-fluid levels: a case report

BACKGROUND: As the third most common malignancy of childhood, Neuroblastoma has a great propensity to metastasize to multiple organs. The most common site of metastasis is the bone and bone marrow. Concerning the central nervous system, neuroblastoma usually involves the calvarium and the external dural surface. The skull metastases may show different appearances, including: multiple lytic bone lesions, bone thickening, hair-on-end periosteal reaction, irregular suture widening and/or plaque like epidural deposits. Here we present a case of metastatic neuroblastoma, appearing as multiple multi-loculated cystic epidural masses with internal blood-fluid levels as a rare imaging manifestation of calvarial metastasis. CASE PRESENTATION: An 8-year-old boy with known history of autism, presented to the emergency department with a 3-month history of intermittent fever, malaise and myalgia and headache along with significant weight loss. Laboratory examination revealed elevated ESR and CRP and anemia. On Abdomino-Pelvic imaging a well-defined, 45*30*24 mm, solid-cystic mass was observed, replacing the normal left adrenal gland. On brain MRI, multiple multi-loculated cystic, lentiform masses were observed on the external surface of cerebral hemispheric dura. Multiple fluid–fluid levels were noted in the locules in some of which the dependent fluid was hyperintense on T1w and FLAIR and hypointense on T2w sequences, compatible with blood, representing blood-fluid level. The wall and septa of the masses, enhanced after contrast administration. Associated abnormal marrow signal and aggressive type periosteal reactions were identified in the overlying bone. All of the lesions had increased uptake in MIBG scan. Bone marrow biopsy revealed small round cells, diagnostic for neuroblastoma. The patient underwent chemotherapy treatment. All calvarial/epidural metastatic lesions resolved after chemotherapy and residual adrenal tumor was resected. CONCLUSION: Cystic epidural lesions, especially when associated with adjacent abnormal bone marrow signal, or periosteal reaction and containing blood-fluid level should raise the suspicion of a calvarial metastasis.