Malignant Sarcomatous Degeneration of Craniofacial Fibrous Dysplasia

Background: Fibrous dysplasia (FD) is an uncommon bone disease characterized by replacement of normal bone architecture with abnormal fibro-osseous connective tissue. Here, we present a unique case of craniofacial FD, with malignant sarcomatous degeneration—a rare and morbid complication of the disease.

Case History: A 36-year-old male previously diagnosed with McCune-Albright Syndrome with a history of multiple craniofacial surgeries at an outside institution presented with a 6-month history of severe left-sided headaches, periorbital pain, nasal obstruction, and midface hypoesthesia. Imaging revealed a heterogenous and expansile lesion with erosive changes in the left nasal cavity and infratemporal fossa ([Fig. 1]).

Initial diagnosis was attributed to aneurysmal bone cyst formation; however, sarcomatous degeneration was considered given the rapid progression of symptoms and growth. Preliminary image-guided core needle biopsy revealed findings consistent with fibrous dysplasia. A strong clinical suspicion for malignancy persisted and the patient underwent an expanded endonasal approach (EEA) for further biopsy and partial debulking.

Pathology demonstrated an atypical fibromyxoid proliferation with osteoid production that did not meet diagnostic criteria for sarcoma though could not rule out low grade sarcoma. Specimens were reviewed at multiple academic institutions for second opinion with similar conclusions. The case was reviewed at a multi-disciplinary tumor conference with consensus recommendations to manage as malignancy in light of the clinical picture. Given the extensive involvement of the skull base, the tumor was deemed unresectable. After molecular diagnostic analysis of the tumor, the patient began neoadjuvant chemotherapy though passed away soon after starting treatment.

Clinical Relevance: Malignant sarcomatous transformation is an extremely rare and challenging complication of craniofacial fibrous dysplasia. Indolent onset, advanced spread at the 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 often be equivocal and may mimic nonmalignant processes, such as locally aggressive fibrous dysplasia. Overall, much remains to be learned about the disease and further studies are needed to better understand the underlying pathophysiology and to develop robust diagnostic criteria.

Fig. 1 T1-weighted MRI demonstrating extent of sarcomatous degeneration in patient with McCune-Albright syndrome.