Primary intraosseous papillary intralymphatic angioendothelioma of the distal femoral epiphysis: a case report with literature review

Papillary intralymphatic angioendothelioma (PILA) is an exceptionally rare metastasizing soft tissue tumor. It tends to arise in the subcutaneous tissues of distal extremities in children. Only four intraosseous PILA cases have been reported until now in English language literature.

We present a case of PILA arising in the distal femoral epiphysis of a 50-year-old female patient. It started as a relentless pain in her left knee. A plain radiography revealed a radiolucent area in the left internal femoral condyle. Computerized tomography revealed a 1-cm lytic lesion with a sclerotic rim. Magnetic resonance images showed a significant bone marrow edema signal focused on a 1-cm subchondral lesion suggestive of an intraarticular osteoid osteoma. Histologically, the tumor contained vascular channels covered by a single endothelial layer with intraluminal papillary endothelial structures lined with hobnail cells. Immunohistochemically, the cells were positive for ERG, CD31, and D2-40. The tumor underwent cryoablation and 6 months later, after local recurrence or tumor persistence, a wide tumor resection was referred. After 7 years of follow-up, the patient displayed neither local recurrence nor distant metastases.

Primary intraosseous PILAs are exceedingly rare tumors that should be considered in the differential diagnosis of vascular bone tumors.