Subcutaneous Lanreotide Depot: A Diagnostic Pitfall in Neuroendocrine Tumor Imaging

Lanreotide depot, a long-acting somatostatin analog, improves progression-free survival in neuroendocrine tumor (NET) patients. However, persistent subcutaneous depots can appear as metastatic lesions on imaging, potentially leading to misdiagnosis. We report the case of a 70-year-old man with grade 2 NET (Ki-67: 5.9%) undergoing six years of lanreotide treatment. Follow-up imaging revealed stable primary disease. However, nodular lesions in the buttock were identified on the CT scan performed eight months after the start of treatment. A retrospective review of a CT scan taken two months after treatment initiation revealed that these nodules were already present and had gradually increased in number, allowing for their correct identification as persistent lanreotide depots. This case underscores the need for heightened diagnostic awareness to prevent unnecessary interventions and ensure accurate management.