renal arteriography.

ultrasonography.

intravenous pyelography.

CT with and without contrast enhancement.

MRI.

Bosniak III cyst.

Bosniak II cyst.

Bosniak IV cyst.

probable angiomyolipoma.

probable malignancy.

Renal oncocytoma

Renal adenoma

Renal angiomyolipoma

Renal metastasis

Renal cell carcinoma

They are best imaged using ultrasound to allow classification using the Bosniak criteria.

They are the most common benign renal lesions found in the kidney.

They rarely require treatment.

They are best characterized using the Bosniak criteria to assess risk of harboring a malignancy.

They can harbor internal septa, calcifications, and internal debris and still be considered benign according to the Bosniak classification.

They can be high grade or low grade, as long as they are less than 3 cm.

Recent studies suggest that renal adenoma may be a premalignant precursor of papillary renal cell carcinoma (RCC).

They are most common in young females.

They are usually of clear cell histology but can also be found with chromophobe and papillary cells as well.

There is uniform agreement regarding the clinical and pathologic classification of renal adenoma.

can be made primarily on the basis of histologic criteria.

requires specific immunohistochemical staining.

is commonly made at autopsy.

can be rendered only if tumor size is less than 1.0 cm.

can be confirmed by electron microscopy.

Renal exploration with biopsy and intraoperative frozen section analysis determining radical versus partial nephrectomy

Partial nephrectomy

A radical nephrectomy without adrenalectomy

A radical nephrectomy with adrenalectomy

Renal exploration, partial nephrectomy with intraoperative frozen section analysis of histology (if malignant, a radical nephrectomy)

laparoscopic exposure and renal cryoablation.

partial nephrectomy.

observation.

radical nephrectomy.

selective embolization.

They are more common in men than in women.

They are complex cystic lesions that are typically classified as Bosniak II.

They are malignant 2% to 5% of the time.

They are characterized by bimodal age distribution.

They are readily differentiated from RCC on the basis of appropriate imaging studies.

female predominance.

specific pattern on immunostain marker panel.

peak incidence in the fifth decade of life.

characteristic appearance on MRI.

benign clinical course.

Small area of less than −20 HU on nonenhanced CT

Enhancement of more than 30 Hounsfield units (HU) on CT

Aneurysmal changes on renal arteriogram

Hyperechoic pattern on ultrasonography

Positive signal on T2-weighted images of MRI

Papillary architecture

Nonconventional histology

Low to moderate grade

Noncentral location

Tumor size less than 3 cm

A 3.0-cm tumor with fat associated with calcification

A 5.0-cm cyst with thin, curvilinear calcification

An 11-cm cyst with water density and a homogeneous nature

A 2.5-cm hyperechoic complex cyst, with no enhancement after intravenous administration of a contrast agent

A 6.0-cm complex cyst with four thin septa

hypervascular pattern.

central, stellate scar on CT.

a spoke-wheel pattern on renal angiography.

trisomy of chromosomes 7 and 17.

multiple mitochondria on electron microscopy.

positive staining for HMB-45.

multiple microsomes on electron microscopy.

a unique cytokeratin expression pattern.

occasional aneuploidy.

positive staining for vimentin.