Angiomyolipoma being surgically excised for presumed kidney carcinoma.
OBJECTIVE
To explore the important factors involved in angiomyolipoma (AML) being preoperatively misclassified and surgically removed for presumed kidney carcinoma.


METHODS
From 2008 to 2014, AML was pathologically confirmed in 38 patients who underwent radical or partial nephrectomy for presumed malignant renal tumor. Control group 1 were patients with renal cell carcinoma (RCC) matched for age and tumor size; control group 2 were patients with typical AML matched for age and sex. Pertinent data of the studied group and its matched control groups were recorded and analyzed.


RESULTS
The mean age of the patients in study group was 48.11 ± 12.92 years, and the mean tumor size was 3.12 ± 1.68 cm (range 0.9-9.4). More than 84 % of the misclassified AMLs measured ≤4 cm, and over 21 % patients underwent radical nephrectomy. The only statistically significant feature between the misdiagnosed AML group and the matched RCC group is mean age (48.11 ± 12.92 vs. 56.92 ± 10.28, P = 0.002). Compared with the matched typical AML group, the misdiagnosed AML group has smaller mean tumor size (3.12 ± 1.68 vs. 5.85 ± 3.33, P < 0.001), but more patients undergoing radical nephrectomy (21.05 vs. 0 %, P = 0.003). Two main imaging features, which are hypoechoic on ultrasonography and fat density on computed tomography (CT), were statistically different between the two groups. The misdiagnosis of AML was significantly associated with no fat density on CT (OR 5.528, P = 0.004) and hypoechoic on ultrasonography (OR 3.845, P = 0.017).


CONCLUSIONS
A number of AMLs were misdiagnosed as RCCs, causing a large number of unnecessary surgeries. No fat density on CT and no hyperechoic on ultrasonography resulting from small tumor size were the two most important factors causing AML being excised for presumed kidney carcinoma. Ultrasonography and CT cannot differentiate atypical AML from kidney carcinoma effectively, so improved renal biopsy and noninvasive biomarkers are urgently warranted to prevent us from excising benign renal tumor aggressively.
Department of Urology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 1#, Shuaifuyuan, Dongcheng District, Beijing, 100730, People's Republic of China.
Weibin
W
Hou
He
H
Xiao
Guanghua
G
Liu
Zhigang
Z
Ji
D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000328:Adult; D018207:Angiomyolipoma / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D002292:Carcinoma, Renal Cell / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D002681:China; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy / Q000379:methods / Q000706:statistics & numerical data; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D014463:Ultrasonography; D019564:Unnecessary Procedures / Q000706:statistics & numerical data