CASE 12823 Published on 13.08.2015

Solitary fibrous tumour of the kidney


Uroradiology & genital male imaging

Case Type

Clinical Cases


Marta E. Hernández García, Begoña Diaz Barroso, Carolina Sainz Azara, Gabriel Olmedilla Arregui, Óscar Rueda Elias, Mª Ángeles Cruz Diaz

Alcalá de Henares

67 years, female

Area of Interest Abdomen, Kidney ; Imaging Technique Experimental, Percutaneous, CT-High Resolution, CT, Image manipulation / Reconstruction
Clinical History
A 67-year-old woman was referred to the digestive health specialist for study of chronic abdominal pain.
Imaging Findings
On CT we observed a well-defined 7 cm solid mass arising from the middle region of the left kidney, with heterogeneous attenuation higher in the periphery. It had small calcifications in the wall. This lesion contacted the left renal artery and vein, which were permeable.
There were small retroperitoneal left-paraaortic lymph nodes, under 5 mm.

At gross pathologic analysis the tumour appeared as a well-defined, firm mass with a grey-white shade measuring 6 x 8 x 7 cm, composed of a proliferation of highly cellular spindle cells with mild atypia. They were arranged in a storiform pattern in some areas and between thick bundles of collagen in other areas.
No significant necrosis, haemorrhage or cellular pleomorphism was seen.
The tumour strongly expressed CD34, vimentin and showed a weak immunohistochemical reaction for Cd99, Bcl2 and HHF-35. There were no reactions for Desmin, EMA, CkAe1-Ae3, melan-a, S-100 or Hmb-45.


Solitary fibrous tumours (SFT) are rare mesenchymal neoplasms. They frequently arise from the serosal surface, most commonly seen in the pleural cavity. Extrapleural SFTs are very uncommon, and to our knowledge, there are less than 50 published cases of SFTs located in the kidney [1]. SFT diagnosis is more frequent during the fifth and sixth decades of life, without significant sex predilection [2].

Histologically, SFTs are distinctive mesenchymal tumours characterized by a well-defined mass composed of a proliferation of spindle cells embedded in a collagenous stroma, with an increase in vascularization with thin-walled blood vessels showing a typical staghorn pattern [3].

The diagnosis is confirmed by characteristic positive immunohistochemical staining for CD34 and negative staining for S-100 [1, 4].
Extrapleural SFTs typically manifest as large, slow-growing soft-tissue neoplasms [4].

Although most extrapleural SFTs have a benign clinical course, up to 15% of these tumours demonstrate aggressive behaviour in the form of recurrence or malignancy [4]
Malignancy probability increases with the size of the tumour [5]

SFT are often incidentally found at CT studies, although their appearance is nonspecific and prompts further investigations [2]
Clinically, most patients are asymptomatic or have pain secondary to a mass effect due to the size of the tumour [6, 7].
The tumour can involve the renal cortex, peripelvis, renal capsule, or extrarenal soft tissue [6]
The radiologic findings of renal solitary fibrous tumour are [2, 6]:
- On ultrasound renal solitary fibrous tumours appear as hypo or heterogeneous echoic masses, and as hypoechoic masses with intratumoural vascularity on Doppler ultrasound.
- Contrast-enhanced CT may reveal a well-circumscribed smooth lobulated solid enhancing mass that contains areas of cystic degeneration.
- MRI usually demonstrates a signal intensity on T1- weighted images and inhomogeneous high or low intensity on T2-weighted images.
In differential diagnosis, the most useful tool is diffuse CD34 positivity to distinguish it from other spindle cell tumours of the kidney [7].
Complete excision and follow-up for recurrence are recommended for both benign and malignant SFT [2, 8].
Differential Diagnosis List
Solitary fibrous tumour of the kidney
Renal cell carcinoma (subtype clear cell)
Mesenchymal tumours
Final Diagnosis
Solitary fibrous tumour of the kidney
Case information
DOI: 10.1594/EURORAD/CASE.12823
ISSN: 1563-4086