Background. Xp11.2 translocation renal cell carcinoma, a rare malignancy, is more common in children than in adults. It manifests with an aggressive course in adults and relatively indolent in children. Prognostic studies for adult patients are scare for the rarity of the disease; and the prognostic value of preoperative plasma fibrinogen awaits further illumination.Methods. This retrospective single-center study enrolled 24 consecutive newly diagnosed Xp11.2 translocation RCC adult patients. Clinical presentations, baseline laboratory results and follow-up data were collected. Possible risk factors for progression free survival and overall survival were first scanned with chi-square tests and t-tests to compare patients who suffered from progression or death and who did not. Multivariate Cox regression was further utilized to identify independent risk factors.Results. Twenty-four adult patients (median age 32, range 16-73), with a male-to-female ratio of 1:1, was included from 2010.4 to 2020.3. After a mean follow-up of 35.7months, seven patients died. With univariate analysis, higher C-reactive protein-to-albumin ratio (p=0.028), higher baseline fibrinogen (p=0.006), and presence of distant metastasis (p=0.007) were associated with progression of disease; higher preoperative fibrinogen (p=0.014) and distant metastasis (p=0.020) were associated with death. With multivariate Cox regression, only baseline fibrinogen level (p=0.001) was identified as an independent risk factor for progression free survival; meanwhile, fibrinogen level (p=0.048) and distant metastasis (p=0.043) were identified as independent risk factors for survival.Conclusions. Preoperative plasma fibrinogen, a routinely tested parameter before surgery, is a promising tool for risk stratification in adult patients with Xp11.2 translocation renal cell carcinoma.JIE et al: Preoperative plasma fibrinogen predicts outcome in Xp11.2 translocation RCC