Introduction and importance: Pseudomyogenic hemangioendothelioma (PMHE) is a rarely metastasizing intermediate endothelial neoplasm. It typically presents as multiple, discontinuous nodules in the lower extremities of young adult males. Most cases present skin or soft-tissue tumors, but intraosseous lesions without soft-tissue involvement are extremely rare. We report a case of PMHE of the tibia, diagnosed with FOSB staining. Presentation of case: A 36-year-old man presented with pain in the lower left leg after exercise and at night. X-ray, SPECT/CT, and MRI revealed two discontinuous lytic lesions within the cortical bone of the left tibia. A curettage procedure was performed for biopsy, but a diagnosis could not be made for a long time. After further consultation, FOSB staining was positive in the nucleus, leading to a definitive diagnosis of PMHE. No recurrence or metastasis was observed 2 years after surgery. Clinical discussion: PMHE is a rare endothelial tumor, and cases limited to bone without soft tissue involvement are exceptional. Diagnosis is difficult because of overlap with myogenic and epithelioid tumors, but nuclear FOSB staining is a reliable marker. Although local recurrence is frequent, metastasis is rare, underscoring the importance of accurate diagnosis and long-term follow-up. Conclusion: This case highlights the importance of considering PMHE in the differential diagnosis of bone tumors, the utility of FOSB immunostaining in confirming the diagnosis, and the need for long-term follow-up given the high risk of local recurrence.
Takada et al. (Mon,) studied this question.