Prospective study of active surveillance, non-randomized, multicentric, in asymptomatic patients over the age of 50 years, not affected by other tumors, with occasional diagnosis of single monolateral solid renal mass equal to or less than 2 cm of diameter. Diagnosis will be performed with chest CT abdomen with contrast and / or MRI abdomen with Gadolinium (Gd); during the first year of active surveillance, the patient's status will be evaluated at 3, 6, 9 and 12 months from the diagnosis and, subsequently, according to the schedule of events shown in the table "Event Planning" At the end of the 5 years of follow up, the patient will be entrusted to his / her own treating physician, with indication to perform abdomen and chest x-ray echography every 6 months and thoracic abdomen TAC with contrast and / or MRI abdomen with (Gd) every 2 years up to 10 years from instrumental radiological diagnosis and registration and communication of the possible date of death and cause The primary caregivers and the patient will be contacted annually by the promoter center of the study at the end of the first 5 years of study follow up and the data will be entered in the database by the promoter center. The indication to surgical treatment or ablative treatment will be considered in the following cases: 1. appearance of metastasis 2. increase of the maximum diameter of the renal mass equal to or greater than 4 cm 3. time of doubling of the tumor mass size less than or equal to 12 months 4. appearance of symptoms associated with renal disease (pain, haematuria) 5. appearance of paraneoplastic syndrome (fever, cachexia, hypercalcemia, polycythemia, ranulocytosis) 6. willingness expressed by the patient to undergo surgery or ablative operation In the presence of at least one of the aforementioned criteria, the attending physician can evaluate the possible execution of renal biopsy. The finding of renal biopsy proved negative for neoplasia may allow the continuation of the active surveillance procedure undertaken, independently indi - ding from the presence of one of the above mentioned criteria. If the renal biopsy is negative, the therapeutic decision (continuation of the follow up within the protocol in question, surgery or exit from the protocol) will be agreed between the patient and the patient. In the case of a positive renal biopsy for renal neoplasia, the patient may be a candidate for renal tumorectomy / radical nephrectomy.

Inclusion Criteria:

1. ability to read, understand and interpret an informed consent;
2. voluntary subscription of the active surveillance protocol through written informed consent; 3) age over 50 years;

4) diagnosis of monolateral, monofocal, and first-rate solid renal mass less than 2 cm; 5) absence of symptoms due to renal tumor pathology.

Exclusion Criteria:

1. patients with a history of previous renal neoplasia;
2. monorenal patients;
3. patients with hereditary renal tumors (such as tuberous sclerosis and Von Hippel Lindau syndrome, etc.);
4. patients with metastasis;
5. patients suffering from immunodepressive diseases;
6. patients on concomitant therapy with chemotherapeutic agents or systemic immunosuppressants;
7. patients with life expectancy of less than 1 year.