Aggressive aneurysmal bone cyst in association with polyostotic fibrous dysplasia: A case report

Fibrous dysplasia imitating malignancy

Fibrous dysplasia is a benign bone disease, presenting as monostotic or polyostotic lesions, or as part of a syndrome (McCune-Albright/Mazabraud). Its clinical course shows a variegated picture and the progression of its growth is unpredictable. In the workup of 39 fibrous dysplasia cases in the cranio-facial area, four cases presented fast growth tendencies, of which two patients with McCune-Albright syndrome showed malignant-like rapid growth. This local aggressive form is extremely rare, and the concept of this issue has not been clearly defined. With regard to the speed of growth a volumetric-time analysis in one of our cases demonstrated a 74 days tumor doubling rate with an exponential growth curve. According to the literature the aggressive form presented extra-cranially mainly at an adult age, whereas its appearance in our cranio-facial patient collective was much younger. Distinguishing nonmalignant and malignant aggressive forms is difficult and highly inconsistent in the literature. We therefore implemented a quantitative growth measure analysis to define aggressive forms based on progression and speed of growth and impartial of type of FD, localization or functional incapacity. Due to our study findings and literature review we state a prevalence of an aggressive form might be possibly about 5 %.

Secondary aneurysmal bone cyst in McCune-Albright syndrome

Polyostotic fibrous dysplasia in combination with caféau-lait macules and hyperfunctioning endocrinopathies consists of a rare clinical condition termed as McCune-Albright syndrome. Aneurysmal bone cysts are tumor-like cystic lesions, composed of blood-filled compartments. They may occur as primary lesions or secondary to other pathologies; most commonly giant cell tumors of bone. However, secondary aneurysmal bone cysts in McCune-Albright syndrome are exceptional. We present a 28-year-old female with McCune-Albright syndrome. She experienced precocious puberty at age 3 months. In childhood, she experienced multiple long bone fractures, facial deformity and progressive visual and hearing impairment. One year ago, she experienced a painful, gradually enlarging bone lesion involving the right ilium, pubic and ischial bone with groundglass appearance, septa, marginal sclerosis, endosteal scalloping and blow-out expansion resulting in localized thinning of the cortex. CT-guided needle biopsy of the pelvic lesion showed aneurysmal bone cyst. Selective arterial embolization was recommended, however, the patient and her relatives did not consent to proceed to treatment, and she remained in close surveillance thereafter.

Diagnosing and discriminating between primary and secondary aneurysmal bone cysts

Aneurysmal bone cysts (ABCs) are benign bony lesions frequently accompanied by multiple cystic lesions and aggressive bone destruction. They are relatively rare lesions, representing only 1% of bone tumors. The pathogenesis of ABCs has yet to be elucidated. In the present study, a series of 22 cases of primary and secondary ABC from patients treated in Department of Orthopedic Surgery, Kagoshima University Hospital (Kagoshima, Japan) from 2001–2015 were retrospectively analyzed. The average age at the time of diagnosis of primary ABC was 17.9 years. Intralesional curettage and artificial bone grafting were performed in the majority of the patients with primary ABC. The local recurrence rate following curettage for primary ABC was 18%, and the cause of local recurrence was considered to be insufficient curettage. Although no adjuvant therapy was administered during the surgeries, it may assist the prevention of local recurrence in certain cases. The cases of secondary ABC were preceded by benign bone tumors, including fibrous dysplasia, giant cell tumors, chondroblastoma and non-ossifying fibroma. The features of the secondary ABC typically reflected those of the preceding bone tumor. In the majority of cases, distinguishing the primary ABC from the secondary ABC was possible based on characteristic features, including age of the patient at diagnosis and the tumor location. In cases that exhibit ambiguous features, including a soft tissue mass or a thick septal enhancement on the preoperative magnetic resonance images, a biopsy must be obtained in order to exclude other types of aggressive bone tumors, including giant cell tumor, osteosarcoma and telangiectatic osteosarcoma.