Follow-up for Bosniak Category 2F Cystic Renal Lesions

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Based on our study findings, 10.9% (17 of 156) Bosniak category 2F cystic lesions progressed to malignancy; therefore, the recommended length of follow-up for the majority of Bosniak category 2F lesions is 4 years.


To determine percentage of Bosniak category 2F complex cystic renal masses that progress to malignancy based on serial follow-up studies,and to determine if there are demographic and/or imaging features associated with progression.

Materials and Methods

This retrospective study was institutional review board–approved with waiver of informed consent. Hospital database system was searched from January 1, 1996, to May 1, 2011, for category 2F cysts studied with contrast agent–enhanced computed tomography or magnetic resonance imaging and followed with serial contrast-enhanced imaging. Demographics of patients and imaging features of lesions that progressed were compared with those that did not. The relationship of these features to progression or stability was assessed by using χ2, Fisher exact, or Cochran Armitage trend tests.


Identified in 144 patients (98 men, 46 women; age range, 31–83 years; average, 63 years) were 156 category 2F lesions. Follow-up studies were from 6 months to 13 years (median, 3.6 years; average, 4.2 years). Nineteen of 156 lesions progressed to category 3 or 4 in 6 months to 3.2 years; 17 lesions (89.5% of those that progressed and 10.9% of initial 2F lesions) were malignant and two were benign. To date, no patients had recurrent or metastatic disease. Men had significant risk for progression to malignancy (P = .003). Of 17 category 2F lesions that progressed to malignancy, 12 were endophytic (P = .02). Category 2F lesions with minimally irregular septa (nine of 17; P= .001) or wall (seven of 17; P = .016), and lesions with indistinct parenchymal interface (nine of 17; P < .001) were associated with progression to cancer. A multilobulated border was not associated with progression (P = .999).


Based on this study, 10.9% (17 of 156) Bosniak category 2F cystic lesions progress to malignancy, and progression occurs within 6 months to 3.2 years.

© RSNA, 2014

Online supplemental material is available for this article.


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Article History

Received December 31, 2012; revision requested February 12, 2013; revision received August 11; accepted September 19; final version accepted March 6, 2014.
Published online: Apr 25 2014
Published in print: Sept 2014