A biopsy is naturally the gold standard in diagnosing extra pulmonary TB in most cases. IGRA as correctly mentioned above may provide supportive evidence of TB. I would, however, be skeptical even if IGRA is positive. There are many diseases that can lead to a false positive IGRA, especially non-tuberculosis mycobacteriums (kansasii, marinum, bovis). Hence, I suggest you focus on what the results of the biopsy reveals and use IGRA as supportive evidence.