Table 1 Detailed distribution of Bosniak-2019 classification and pathology results in the training cohort and external validation cohort

Training cohort

Bosniak I (n = 59)

Simple renal cysts (n = 59)

(n = 0)

Bosniak II (n = 23)

Simple renal cysts (n = 21)

Papillary renal cell carcinoma (n = 1) tubulocystic renal cell carcinoma (n = 1)

Bosniak

Simple renal cysts (n = 9)

Tubulocystic renal cell carcinoma (n = 2)

IIF

Cystic nephroma (n = 1)

Papillary renal cell carcinoma (n = 1) clear cell renal cell carcinoma (n = 3)

(n = 22)

Renal angiomyolipoma (n = 2)

Multilocular cystic renal neoplasm of low malignant potential (n = 4)

Bosniak

Simple renal cysts (n = 5)

clear cell renal cell carcinoma (n = 6) papillary renal cell carcinoma (n = 1)

III

Cystic nephroma (n = 1)

Chromophobe renal cell carcinoma (n = 1) tubulocystic renal cell carcinoma (n = 1)

(n = 18)

Renal angiomyolipoma (n = 1)

Multilocular cystic renal neoplasm of low malignant potential (n = 2)

Bosniak

Renal angiomyolipoma (n = 2)

Unclassified renal cell carcinoma (n = 5) clear cell renal cell carcinoma (n = 19)

IV

Papillary renal cell carcinoma (n = 5) chromophobe renal cell carcinoma (n = 2)

(n = 37)

Cystic nephroma (n = 2)

Multilocular cystic renal neoplasm of low malignant potential (n = 2)

Testing cohort

Bosniak I (n = 19)

Simple renal cysts (n = 19)

(n = 0)

Bosniak II (n = 11)

Simple renal cysts (n = 11)

(n = 0)

Bosniak IIF

Simple renal cysts (n = 16)

Clear cell renal cell carcinoma (2)

(n = 20)

Mixed epithelial and stromal tumor (1)

Multilocular cystic renal neoplasm of low malignant potential (1)

Bosniak III (n = 6)

Simple renal cysts (n = 5)

Clear cell renal cell carcinoma (1)

Bosniak IV (n = 7)

Cystic nephroma (1)

Clear cell renal cell carcinoma (5)

Multilocular cystic renal neoplasm of low malignant potential (1)