British Journal of Radiology (2004) 77, 782-783
© 2004 British Institute of Radiology
doi: 10.1259/bjr/33776173
Renal angiomyolipoma with calcification: CT–pathology correlation
S Merran, MD
1
A Vieillefond, MD
2
M Peyromaure, MD
3 and
C Dupuy, MD
4
1 FMP Département d'Imagerie Médicale, 24 rue saint Victor, 75005 Paris, Hôpital Cochin Service, 2 d'Anatomopathologie, 3 d'Urologie, 35 rue du faubourg St Jacques, 75014 Paris and 4 FMP Consultation de Médecine générale, 24 rue saint Victor, 75005 Paris, France
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Abstract
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Fat containing renal tumours are usually considered as angiomyolipomas on imaging modalities. Some cases of renal cell carcinoma have been reported. Although it has been previously reported, angiomyolipomas containing calcifications are very rare. We report a case of a fatty renal tumour with calcification which was an angiomyolipoma. The calcification within the tumour was secondary to osseous metaplasia.
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Case report
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Fat containing renal tumours on CT examination are considered to be angiomyolipomas (AMLs). Several cases of renal cell carcinomas containing macroscopic fat have also been reported [1–6]. Only a very few cases of AML with macroscopic calcification have been reported [7–9]. We report a new case of an isolated AML with calcification visible on CT.
A 64-year-old female, presented with gross haematuria. Ultrasound showed a hyperechoic mass of the posterior aspect of the midpole of left kidney. An unenhanced CT scan showed a fat-containing left renal mass with a solid nodule and a focus of calcification (Figure 1
).
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Figure 1. CT of the angiomyolipoma of the left kidney without contrast medium injection: (a) fatty component (arrow); (b) solid nodule (double arrow); (c, d) calcification (arrowhead).
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Although the amount of fat was considered compatible with a diagnosis of an AML, according to previous reports [1–6] the diagnosis of renal cell carcinoma was raised and the patient underwent partial nephrectomy to exclude this. Tumourectomy was performed and peroperative pathology diagnosed a typical AML. After resection of the entire lesion, histopathology examination oriented by the CT features enabled the identification of the calcification within the AML (Figure 2).
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Figure 2. Histology ( x 40 haematoxylin anal eosin stain) at the level of the calcification visible on CT detail of the angiomyolipoma with the muscular and adipose components engulfed by focal fibrosis and a "scar" of osseous metaplasia.
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Discussion
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AML are benign renal tumours occurring either in isolation (80% of cases) or as multiple lesions associated with tuberous sclerosis (20% of cases) [10]. AMLs contain a variable amount of fat allowing the diagnosis to be made from CT examinations. Some other solid renal tumours contain fat including renal cell carcinomas [1–6]. All reported cases of renal cell carcinomas containing fat also contained calcification. In a review article previously published [4] we concluded that fat and calcification within the same tumour are highly suggestive of renal cell carcinoma. Only three papers report AML containing areas of calcification [7–9].
Multiple mechanisms have been advocated to explain calcification and fat within a renal mass [4]. In our case osseous metaplasia associated with a fibrous scar explains the calcification in the AML.
A review of the different reported cases of renal tumours containing fat and calcification allowed us to suggest that when the fat component is pre-eminent the diagnosis of AML is more likely, on the other hand when the fatty component is subtle and the calcifications bigger than the fatty part the diagnosis of renal cell carcinoma is more likely.
Received for publication February 21, 2003.
Revision received August 15, 2003.
Accepted for publication December 18, 2003.
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References
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Abstract
Case report
