Bone Cancer

Diffuse nuclear "TPIT" staining with OTI2G1 in chordoma reflects cross-reactivity driven by conserved T-box structure rather than true TBX19 expression. For the differential diagnosis of sellar lesions, especially poorly differentiated chordoma versus pituitary neuroendocrine tumor, use of more specific clones (eg, CL6251) is recommended.

MT in denosumab-treated GCTB is rare and does not appear more frequent than historical baseline rates, but it predominantly affects a biologically and clinically high-risk subgroup. Vigilant clinical and radiological surveillance, prompt re-biopsy of atypical lesions, and referral to expert sarcoma centers are essential, and prospective registries with integrated molecular profiling are urgently needed.

P2, N=30, Active, not recruiting, Dana-Farber Cancer Institute | N=45 --> 30

These cases reinforce that preoperative CNB with a targeted immunohistochemistry panel - explicitly distinguishing GCTB from ectopic axillary breast carcinoma - should be strongly recommended for any suspicious axillary tail mass; Case 1, in which the patient declined CNB and proceeded directly to surgery, illustrates by counter-example the diagnostic uncertainty that results when this step is omitted. We present these cases in accordance with the CARE reporting guidelines.

The results suggest the potential involvement of CXCR4 in the pathogenesis of giant cell granulomas of the jaws and GCTB. This chemokine receptor may also contribute to differences in the biological behavior of these MGC-containing lesions. The relevance of CXCL12 for the development of the giant cell lesions studied appears to be variable.

P3, N=40, Active, not recruiting, Daiichi Sankyo Co., Ltd. | Trial completion date: Feb 2026 --> Mar 2027

Treatment was well tolerated and associated with durable radiographic response with tumor reduction, partial metabolic response on FDG-PET imaging, and clinically significant improvement in neurological symptoms and quality of life. This case highlights the value of molecular tumor board-guided interpretation of genomic alterations and illustrates the potential role of IDH-targeted therapy in select patients with recurrent chordoma.

This case supports the existence of a shared pathogenic mechanism linking PPGLs and GCTBs, likely mediated by postzygotic H3F3A mutations. Recognition of this association is crucial for early diagnosis, genetic counseling, and management of similar cases.

P1/2, N=120, Active, not recruiting, Deciphera Pharmaceuticals, LLC | Trial primary completion date: Jul 2026 --> Aug 2028

P2, N=9, Completed, Daiichi Sankyo Co., Ltd. | Active, not recruiting --> Completed

CYP26A1 expression was most frequent in giant cell tumors of bone. While also detected in a subset of other bone tumors, expression was limited or absent in most benign and malignant lesions, and entirely absent in normal bone tissue. These findings provide novel descriptive insight into CYP26A1 distribution and support further investigation into its role in retinoid-related pathways in bone tumor biology.

Stromal p63 and CD10 were commonly expressed in GCTB. CD10-high expression was associated with recurrent-case status in univariate analysis, but this exploratory finding should not be interpreted as recurrence prediction.