Retroperitoneal hamartoma mimicking angiomyolipoma: a case report and review of literature

Background Hamartoma refers to the excessive focal growth of cells and tissues in organs, which is between malformation and benign tumor. Hamartomas are commonly seen in the lung, but rare in the retroperitoneum. Main text Angiomyolipoma was also called hamartoma in the early years. Hamartoma was not separated from the concept of angiomyolipoma until perivascular epithelioid cells were found in angiomyolipoma. We reported a case of retroperitoneal hamartoma, which was suspected to be angiomyolipoma in the initial imaging findings and pathological frozen section, but the paraffin section was finally diagnosed as hamartoma. Due to the fusion of the tumor with the right psoas major muscle, it may need to be cut off for complete resection of tumor, which may damage the sacrococcygeal nerve and affect the postoperative activity function, so the tumor was just partially removed. After 6 and 22 months of follow-up, the patient was in good condition. CT re-examinations showed that the epibiotic right retroperitoneal mass size was 40 × 42 × 72 mm 3 (6 months, length × width × height) and 40 × 45 × 81 mm 3 (22 months, length × width × height). We describe this case and review the literature. Conclusions In conclusion, retroperitoneal hamartoma is rare and difficult to differentiate from angiomyolipoma, in which perivascular epithelial cells could be found on pathological paraffin sections.