Calvarial Lesions in a Cadaver with Metastatic Osteosarcoma: A Case Study and Differential Diagnoses

Introduction

This case study aims to investigate suspicious bony lesions on the calvarium of a 22-year-old cadaver whose cause of death was reported to be respiratory failure/metastatic osteosarcoma. Respiratory failure, left total femur replacement, and evidence of metastasis to the lungs raise suspicion for widespread metastatic disease. This case study aims to investigate the observed lesions and review potential differential diagnoses for the bony skull-based lesions observed in this cadaver.

Methods

A right-sided frontotemporal protrusion was identified on examination of the cadaver’s face and head during gross anatomy lab. Further dissection revealed erythematous, thickened bony lesions localized to the right frontal and temporal bones of the calvarium. These lesions were located epidurally and traversed the full thickness of the calvarium, appearing on both the outside and inside of the skull on the bilateral temporal bones and on the right side of the frontal bone. X-ray imaging was performed on the calvarium to evaluate for radiologic findings of cranial bone metastasis.

Results

X-ray imaging of the calvarium demonstrated lytic, hypodense lesions within the bilateral temporal bones with slight extension of the lesions into the frontal bone. This morphology is not consistent with the classical radiologic findings of osteosarcoma, which is commonly described as a “sunburst appearance.” However, skull-based tumors are less likely to present with this classic appearance. This non-characteristic appearance on imaging prompted a deeper investigation into differential diagnoses for skull-based lesions in this cadaver.

Outside of metastasis, other potential causes of lytic bone lesions of the skull include multiple myeloma, Langerhans cell histiocytosis, and trauma. Less likely of these choices would be multiple myeloma, as the patient profile and imaging findings are not consistent with that of this cadaver. Langerhans cell histiocytosis presents most commonly in pediatric patients. The epidural location of the findings could suggest an epidural hematoma; however, the full-thickness nature of the lesions, lack of extension to suture lines, and intact calvarium without fracture make trauma less likely. The most likely of these differentials would be metastases, which is greatly supported by the already present multiple metastases to the lungs.

Discussion

This case highlights a potential instance of osteosarcoma metastasis to the calvarium, which has been found to occur in only about 6% of cases. It also highlights the importance of considering a list of differential diagnoses in patients with ongoing metastatic disease. Osteosarcoma metastasizes hematogenously, and calvarial metastasis could occur via pulmonary shedding or retrograde flow through Batson’s Vertebral Venous Plexus. For further assessment and confirmation, a biopsy of the lesions with histopathology should be considered.