Malignant transformation of a highgrade osteoblastoma of the petrous apex with subcutaneous metastasis

Abstract

We describe the clinical presentation, management, and pathologic findings in a case of osteosarcoma of the petrous apex with an atypical metastasis to the lower abdominal wall. We retrospectively reviewed the record of a 49-year-old man who was diagnosed with a rightpetrous apex lesion, which biopsy identified as a high-grade osteoblastoma. After two attempts at en bloc resection were not curative, radiation and chemotherapy wererecommended. TIle patient subsequently developed a cutaneous lowerabdominal mass that was diagnosed asan osteosarcoma. Meanwhile, the petrousapex tumor continuedtogrowdespite treatmentuntil thepatientdied from theburden ofdisease. Temporal boneosteoblastomas and osteosarcomas are both extremely rare, and they can be difficult to differentiate histologically. Our case illustrates this difficulty and demonstrates the possibility of a high-grade osteoblastoma's malignantconversion to an osteosarcoma.