Malignant Sarcomatous Degeneration of Craniofacial Fibrous Dysplasia.

BACKGROUND: Fibrous dysplasia (FD) is an uncommon bone disease characterized by the replacement of normal bone architecture with abnormal fibro-osseous connective tissue. Here, we discuss 2 cases of craniofacial FD, with malignant sarcomatous degeneration - a rare and morbid complication of the disease. CASE HISTORY: Two cases of craniofacial FD with malignant degeneration are presented. In the first, a 68-year-old male with a history of FD presented with acutely worsening left-sided facial pain and V2 and V3 hypoesthesia. Imaging findings suggested a large infratemporal fossa mass with biopsy demonstrating sarcomatous degeneration. Radical craniofacial resection achieved a gross total resection with likely microscopic disease. The patient was unable to tolerate adjuvant chemotherapy or radiation and succumbed to his disease 13 months following surgery.In the second case, a 36-year-old male with McCune-Albright Syndrome and craniofacial FD presented with acutely worsening left-sided headaches and midface hypoesthesia. Imaging revealed a heterogenous and expansile lesion with erosive changes in the left nasal cavity and infratemporal fossa. Pathology was suggestive of low grade sarcomatous degeneration. Given the extensive involvement of the skull base, the tumor was deemed unresectable, and the patient soon died following initiation of chemotherapy. CLINICAL RELEVANCE: Malignant sarcomatous transformation is a rare and challenging complication of craniofacial FD. Indolent onset, advanced spread at time of presentation, and close relationship with vital neurovascular structures are all hurdles for the treating clinician. The entity poses a diagnostic dilemma, as pathological analysis can be equivocal and may mimic nonmalignant processes, such as locally aggressive FD.