Soft tissue sarcomas (STS) require accurate biopsy for diagnosis, grading, and management decisions. Although tru-cut biopsy is widely used, the optimal needle gauge remains uncertain. This study aimed to compare diagnostic accuracy and biopsy concordance rates of 14 G, 16 G, and 18 G tru-cut biopsy needles for extremity STS.

1. Is there any difference between the diagnostic accuracy measurements of 14G, 16G and 18G tru-cut biopsy needles for diagnosis of soft tissue sarcomas in extremities?
2. Do tumor size, tumor depth, tumor subtype and histological grade of the tumor affect the "matching score"s of biopsies?
3. Do tumor size, tumor depth, tumor subtype and histological grade of the tumor affect the biopsy result concordance and/or diagnostic accuracy measurements?
4. Does needle gauge effect successful tumoral tissue sampling or prediction of histological grade of soft tissue sarcomas?

In 2018, the National Comprehensive Cancer Network (NCCN) endorsed core-needle (tru-cut) biopsy as the preferred diagnostic modality for STSs [14]. They recommend obtaining at least three tissue core blocks through a single stab incision on the skin, with a 14-gauge needle, directing the needle along different trajectories. In clinical practice, both 14 G and 16 G cores are commonly used Although multiple tru-cut needle gauges are used in practice, to our knowledge, an ideal and safe biopsy needle that does not sacrife diagnostic performance has not been defined. This is a randomized prospective disagnostic accuracy study. Therefore we prospectively compared numerous variables (tumor size, tumor depth, subtype, histological grade etc.) with biopsy result concordance and diagnostic accuracy of 14 G, 16 G, and 18 G tru-cut needles in samples obtained from the same tumor for each patient with suspected extremity STS, to determine whether an optimal needle gauge exists.

Inclusion Criteria:

• Patients presenting to the Orthopedic Oncology outpatient clinic at Ankara Bilkent City Hospital with suspected or preliminary findings on physical examination suggesting soft tissue sarcoma.

Patients presenting to the Orthopedic Oncology outpatient clinic at Ankara Bilkent City Hospital with suspected or preliminary findings on radiological imaging suggesting soft tissue sarcoma.

Patients with soft tissue masses in extremities which require pathological examination

Exclusion Criteria:

• Patients with a prior diagnosis of the existing mass, coagulation disorders, active infection at the tumor site, a history of previous surgery or radiotherapy to the tumor region, medical conditions contraindicating tru-cut biopsy, or those who did not consent to participate after detailed explanation of the study, were excluded.

IPD will no affect the study results or analysis.