Primary splenic angiosarcoma presenting with multiple bone destruction as the initial manifestation: a case report and narrative review.

Background: Primary splenic angiosarcoma (PSA) is an extremely rare and highly aggressive malignant vascular tumor. Its clinical presentation is often nonspecific, and the diagnosis is frequently delayed. Osseous metastasis as the initial clinical manifestation is particularly uncommon, posing significant diagnostic challenges. A critical yet underappreciated phenomenon is the discordance between histological differentiation and biological behavior in angiosarcoma: well-differentiated tumors can exhibit highly aggressive clinical courses. Furthermore, biopsy of vascular tumors carries a substantial risk of intractable hemorrhage, a complication that is often underestimated. Case introduction: We report the case of a 56-year-old female who presented with a 20-day history of lower back and right hip pain. Imaging revealed multiple osteolytic lesions involving the thoracolumbar vertebrae, pelvis, and sacrum, as well as multiple nodular lesions in the spleen. The initial clinical suspicion favored metastatic disease of unknown primary. Ultrasound-guided needle biopsy of the right iliac lesion yielded abundant hemorrhage but no definitive malignant tissue on initial pathology. Subsequent open biopsy of the L2 spinous process and right iliac bone resulted in life-threatening hemorrhage, necessitating emergency digital subtraction angiography (DSA) and super-selective embolization. Histopathological examination of the surgical specimens revealed a mixed-type vascular neoplasm with partially well-differentiated angiosarcomatous changes, with immunohistochemical positivity for CD31, CD34, ERG, and Fli-1. Remarkably, follow-up pelvic MRI performed only 21 days after the initial scan demonstrated interval enlargement of multiple bone lesions, indicating extraordinarily rapid disease progression despite the high-grade histological appearance. Conclusion: This case highlights several critical clinical considerations for angiosarcoma: (1) When both splenic and skeletal lesions coexist, suspected primary splenic angiosarcoma with bone metastases should be strongly considered; (2) The histological grade may be discordant with biological behavior-high-grade tumors can exhibit highly aggressive courses; (3) Imaging features can mimic benign vascular tumors such as hemangioma; (4) Biopsy of vascular tumors carries a substantial risk of intractable hemorrhage, and pre-procedural angiographic assessment should be considered. This case underscores the importance of integrating clinical, imaging, and pathological findings for accurate diagnosis and management of this rare malignancy.