Objective: Giant cell tumor of bone (GCTB) is a rarely metastasizing, locally aggressive tumor. Recurrence and metastasis in GCTB are thought to be driven by the biological behavior of the neoplastic stromal mononuclear cells. Several pathophysiological mechanisms, including expressions of p63, RANK, RANKL, and VEGF, have been proposed to influence this aggressive potential. This study aimed to identify histomorphological and immunohistochemical parameters that may predict recurrence and metastasis in patients with GCTB.

Material and Methods: This retrospective study included 32 GCTB patients. Clinical, radiological, and pathological data were reviewed. Histomorphological features, including surgical margins, bone cortex invasion, soft tissue invasion, mitotic count, vascular invasion, percentage of spindle cell areas, and presence of tumor-associated lymphocytes (TALs), along with tumor size and demographic features, were evaluated. Tissue sections were stained with p63, RANK, RANKL, and VEGF. The relationship between these parameters and post-surgical recurrence or metastasis was analyzed.

Results: A higher percentage of spindled pattern was significantly associated with a lower frequency of recurrence. A larger tumor diameter at diagnosis was associated with the development of metastasis. Other histomorphological parameters and the expression of p63, RANK, RANKL, and VEGF were not significantly associated with recurrence or metastasis.

Conclusion: Percentage of spindled pattern and primary tumor diameter are potential prognostic factors for recurrence and metastasis, respectively, in GCTB.