Type:
Educational Exhibit
Keywords:
Neoplasia, Cysts, Cancer, Contrast agent-intravenous, Ultrasound, MR, CT, Oncology, Kidney, Abdomen
Authors:
S. Pellegrino, D. Giambelluca, G. Caruana, M. Dimarco, D. Picone, T. V. Bartolotta, G. Salvaggio, G. Lo Re, R. Lagalla; Palermo/IT
DOI:
10.1594/ecr2018/C-0818
Background
The detection rate of renal masses has increased in the last decades owing to the widespread use of imaging techniques.
Therefore,
an accurate characterisation is essential to ensure appropriate case management [1].
The approach to a renal mass first begins with an image analysis to be sure that the finding is indeed a true renal mass.
Conditions that mimic a renal mass should be excluded [2].
Trauma,
infarction,
hemorrhage,
and infection may be incidental; each of these conditions can cause mass-like enlargement of a portion of the kidney and mimic a solid or cystic neoplasm (Fig 1).
Renal masses may be subdivided into cystic and solid masses.
- Cystic renal masses are composed predominantly of spaces filled with fluid.
Bosniak classification,
introduced 20 years ago,
is a practical and useful guide to the diagnosis and management: five categories of cystic renal masses are included,
ordered in increasing probability of malignancy.
Size is not an important feature of the Bosniak classification; small cystic masses may be malignant and large ones may be benign.
However,
small cystic renal masses are more likely benign,
but large ones are not necessarily more likely malignant [2] (Fig 2).
- Solid masses contain little or no fluid components.
With regard to the management of solid renal neoplasms,
it is important to know whether there is a known primary malignancy.
When there is a history of an extrarenal primary tumor,
only 50%–85% of solitary renal masses are metastatic [2].
If multiple renal masses are discovered incidentally in the absence of a known primary malignancy,
metastatic disease is less likely [2] (Fig 3).
In adults,
most solitary solid renal neoplasms found at imaging,
that do not contain fat,
are renal cell carcinoma.
However,
a substantial fraction of solid renal masses are benign.
A useful strategy for the evaluation of renal masses is to divide them on the basis of their growth pattern into balltype or bean-type masses [3].
- Ball-type masses are more common and enlarge by means of additive expansion.
As they grow,
these spherical masses can deform the renal contour,
producing a hump or bulge.
- Bean-type lesions use the tissues of the renal parenchyma as scaffolding for infiltrative growth.
While the process can enlarge the kidney,
its reniform shape typically is maintained [3].
The different imaging modalities,
including computed tomography (CT),
magnetic resonance (MRI) and ultrasound (US) play a crucial role in the evaluation and classification of renal lesions.