Renal Cysts – What is new with Bosniak Classification?

• 10 Feb 2021 10:43:52 AM
• |Onco Urology

Dear All,

Classification of Renal Cysts have been based on what Bosniak introduced in 1986 based on CT evaluation but has undergone Changes periodically. The first major change from Bosniak 1986 was introduction of Grade 2F in 2005 but gained prominence in 2012 with the article from Bosniak ‘Bosniak classification revisited 25 yrs later’ in 2012. What is still undefined, however, is for how long surveillance needs to continue. The incidence of malignancy in Bosniak 2F cysts that do not change character is only 1%. Conversely, a Bosniak 2F cyst that advanced to be a Bosniak 3 or 4 lesions during radiographic surveillance (which occurred in 12% of cases) was associated with a high rate of malignancy of 85%.

There is still no consensus as how long these category cysts should be followed up. Many consider a period of 3 to 5 years is satisfactory.

As regards Grades 1, 2F and 4, there are hardly any controversies as regards their policies for treatment. However, recently considerable controversy has emanated as regards Grade 3. Schoots et al (2017) studying Renal Cysts came to the conclusion that many of the grade 3 cysts were being overtreated.

There are some studies indicating that smaller size Grade 3 Cysts harbour malignant nature than larger cysts of same category. Cameron Jonathan Lam, Anil Kapoor (2018) studying the risk of malignancy in Grade 3 Renal Cysts stated that the malignancy risk of Bosniak III renal lesions was 60% in their study. All Bosniak 3 lesions were of low Fuhrman grade with no evidence of progression. No patient in this study developed metastatic disease within the three-year followup period.

Of late CT and MRI are used for classifying Renal Cysts. Though both classifications are similar, there are few small changes in description. Repeated use of CT induces considerable radiation effect and the same with MRI becomes expensive.

The use of ultrasound (US) in the Bosniak classification has never been unquestionably accepted, as the detection of neovascularization in malignant lesions, indicated by contrast enhancement of solid components, septa or walls, is a fundamental part of the classification. BB McGuire, JM Fitzpatrick (2010) suggested that simple (Bosniak I) and minimally complex (Bosniak II) cysts may be followed with US only. The same was reiterated by Valdair F Muglia and Antonio Carlos Westphalen (2014). They mentioned an advantage of US is its capacity of defining the cystic or solid nature of the lesion. The characterization of remarkably hypovascular lesions may be difficult on CT. The papillary renal cell carcinoma is an example of such tumours and its diagnosis may be difficult if the change in density between pre- and post-contrast phases approaches pseudo-enhancement values (10 HU for 16 Channel MDCT and 20 HU for 64 Channel MDCT). In addition to their hypovascular nature, papillary tumors present cystic degeneration with a frequency similar to the clear cell variant.

Ginil Kumar presented the Utility of CA9 Assay for detection of malignant Cystic Renal Lesions as a poster for AUA (which I remember received a poster award) and his team with Himesh Gandhi presented this work for CKP Menon award at USICON 2015.

https://www.amrita.edu/sites/default/files/poster.pdf

I am providing two links addressing the current concepts on Classification of Renal Cysts and also a PDF article. These read together will enhance our knowledge on Renal Cysts

https://pubs.rsna.org/doi/pdf/10.1148/radiol.2019182646

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5994987/pdf/cuaj-6-e276.pdf

With warm regards,

Venu 

 

 

 

View Document