Unusual Histopathological Challenges in Diagnosis of Giant Cell Tumor Cases Treated with Neoadjuvant Denosumab...

Giant cell tumor of bone (GCTB) is a rare yet locally aggressive neoplasm primarily affecting young adults. Its hallmark features include multinucleated osteoclast-type giant cells and mononuclear tumor cells. Treatment with denosumab, an anti-RANK ligand antibody, has shown efficacy, but it alters histomorphology, posing diagnostic challenges. Co-occurrence with achondroplasia, though rare, warrants consideration in bone lesion evaluations.

A 30-year-old male with achondroplasia presented with a proximal femur GCT, a rare association. Neoadjuvant denosumab was administered due to thin tumor cortex and cortical breech. Surgical excision with bone cement filling and Philo's plate supplementation was performed. Histopathological examination post-treatment revealed the absence of osteoclast-type giant cells, extensive necrosis, hyalinization, and mononuclear infiltrates.

Denosumab induces a reduction in osteoclast numbers, causing tumor shrinkage and sclerosis, while altering typical GCT histology. Similar findings were noted in the literature, including stromal changes like spindle-shaped cells, inflammation, vascular proliferation, and hemosiderin-laden foamy macrophages. Recognition of these alterations is crucial for accurate diagnosis.

GCT, though rare, presents distinct histopathological features aiding diagnosis. Denosumab treatment modifies tumor morphology, necessitating thorough clinical evaluation for accurate diagnosis post-treatment. Understanding, these challenges is essential for optimal management of GCT cases.