Primary Presacral Neuroendocrine Tumor Presenting as Multiple Liver Metastasis: A Case Report

BACKGROUND Various neoplasms, including neuroendocrine neoplasms (NENs), can arise from the presacral space. Most presacral lesions are detected due to symptoms arising from tumor growth. However, diagnosing small, asymptomatic presacral tumors is challenging because of their unique location. CASE REPORT A 63-year-old woman with chronic hepatitis C underwent follow-up after achieving a sustained virological response. Abdominal ultrasonography revealed multiple new hyperechoic masses in the liver. Physical and laboratory examinations, including tumor marker analysis, yielded unremarkable results. Computed tomography (CT) and magnetic resonance imaging (MRI) indicated metastatic liver tumors but failed to identify the primary site of these lesions. The hepatic mass was biopsied, leading to a diagnosis of grade 2 neuroendocrine tumor. 111In-pentetreotide somatostatin receptor scintigraphy revealed significant radiotracer accumulation in multiple hepatic masses, several bones, and a small presacral space lesion. Pathological examination of the presacral lesion confirmed a grade 2 neuroendocrine tumor, similar to the hepatic mass. Review of a CT scan performed 4 years earlier indicated a small cyst-like lesion in the presacral space suspected of being a developmental cyst; however, the presence of cystic components was not confirmed pathologically. The patient was diagnosed with a primary presacral neuroendocrine tumor, which might have originated from a developmental cyst, with multiple liver metastases. Chemotherapy with everolimus was initiated, and the clinical course has been uneventful. CONCLUSIONS We report a rare neuroendocrine tumor arising from the presacral space with multiple liver metastases. The presacral space should be examined when a NEN with an unknown primary site is found.