Dramatic response of aneurysmal bone cyst to denosumab: Case report and literature review

Botulinum toxin: a new differential diagnosis for a lytic bone lesion

BACKGROUND

Botulinum toxin, produced by the Gram-positive anaerobe Clostridium botulinum, is composed of seven antigenic subtypes (A, B, C, D, E, F, and G). Currently, only Botulinum toxin type A, commonly referred to as "Botox," is approved for clinical use, given its relatively safe clinical profile. Botulinum toxin type A has a wide range of therapeutic indications, including treatment for dystonia, migraine headache, neurogenic bladder, and large muscle spastic disorders. However, the toxin is most widely known for its cosmetic effects in treating wrinkles and facial lines.

CASE PRESENTATION

This article describes a 62-year-old Caucasian female who presented for investigation and workup of an isolated lytic lesion of her frontal bone a few weeks after administration of botulinum toxin injection into the corresponding site in the frontalis muscle. This presented as a large, palpable, painless forehead lump causing significant psychological distress. After no neoplastic cause for the lesion was found and histopathology was performed, our researchers concluded that the most likely explanation was that the bony lytic lesion resulted from inadvertent injection of the "Botox" neurotoxin through the intended target muscle and into the cortex of the underlying bone.

CONCLUSIONS

Our search of the literature failed to identify any previous cases of this occurring. However, as the popularity of this cosmetic procedure only increases, we believe that this represents an important possible differential for isolated lytic lesion after administration of "Botox" injection.

The role of neoadjuvant denosumab in the treatment of aneurysmal bone cysts: a case series and review of the literature

OBJECTIVE

Aneurysmal bone cysts (ABCs) are benign cystic lesions most commonly occurring in the long bones of pediatric patients. Spinal ABCs may be difficult to resect given their invasive, locally destructive nature, proximity to critical structures such as the spinal cord, and their intrinsic hypervascularity, for which complete embolization is often constrained by radiculomedullary segmental feeders. Denosumab, a monoclonal antibody that binds the receptor activator of nuclear factor kappa B (NF-κB) ligand, has been utilized in the treatment of ABCs most often as a rescue therapy for recurrent disease. Here, the authors present 3 cases of neoadjuvant denosumab use in surgically unresectable tumors to calcify and devascularize the lesions, allowing for safer, more complete resection.

METHODS

This is a single-center, retrospective case series treated at a tertiary care cancer center. The authors present 3 cases of spinal ABC treated with neoadjuvant denosumab.

RESULTS

All 3 patients experienced calcification, size reduction, and a significant decrease in the vascularity of their ABCs on denosumab therapy. None of the patients developed new neurological deficits while on denosumab. Subsequently, all underwent resection. One patient continued denosumab during the immediate postoperative period because a subtotal resection had been performed, with stabilization of the residual disease. No complications were associated with denosumab administration.

CONCLUSIONS

The use of denosumab in unresectable ABCs can cause calcification and devascularization, making safe resection more likely.