Editing Kidney Cancer: Diagnosis and Evaluation (section)

===== Findings =====

*'''<span style="color:#ff0000">Enhancement'''
** <span style="color:#ff0000">'''Hounsfield units (HU) are a standardized quantitative measurement of x-ray attenuation'''</span>[https://pubmed.ncbi.nlm.nih.gov/29362150/]
**'''If homogenous lesion and HU on non-contrast CT is[https://pubmed.ncbi.nlm.nih.gov/29362150/]'''
***'''<span style="color:#ff0000"><20, then simple cyst'''
***'''>70, then hemorrhagic/proteinaceous cysts'''
***'''20-70, then considered indeterminate and warrants further evaluation'''
**'''<span style="color:#ff0000">On contrast-enhanced CT, if change in HU (compared to non-contrast)</span>[https://pubmed.ncbi.nlm.nih.gov/29362150/]'''
***'''<span style="color:#ff0000">>20, then considered enhancing</span>'''
***'''<10, then no enhancement'''
***'''10-20, then indeterminate enhancement'''
**'''<span style="color:#ff0000">Differential diagnosis of an enhancing renal mass on CT scan[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5258153/]</span>'''
***'''<span style="color:#ff0000">Hyperdense cyst</span>'''
****'''Hyperdense cysts are benign lesions that contain old, degenerated, or clotted blood and have increased CT attenuation (>20 HU)'''
***'''<span style="color:#ff0000">Renal cell carcinoma</span>'''
****'''<span style="color:#ff0000">Any solid renal mass that enhances >15 Hounsfield units and does not exhibit fat density should be considered a renal cell carcinoma (RCC) until proven otherwise</span>'''
***** '''Clear cell enhances more than papillary and chromophobe RCC'''
****** Emerging data suggests that clear cell RCC may be distinguished from the papillary subtype (papillary RCC is often hypo-enhancing). However, both malignant and benign masses can display heterogeneous avid contrast enhancement patterns and no definitive conclusion can be drawn regarding biological potential based on enhancement pattern alone
** '''<span style="color:#ff0000">Solid masses that have substantial areas of negative CT attenuation (<-20 HU) indicative of fat are diagnostic of AML'''
*** '''≈5-10% of AML’s are fat poor'''
*** '''In rare instances RCC may demonstrate fat''' density on imaging and even pathologically, '''but this is the exception rather than the rule'''
* '''Tumors with calcification associated with fat are uncommon but are almost always malignant RCC.'''
** In this setting the fat is thought to be a reactive process related to tumor necrosis.
** Calcification is virtually never seen in association with AML.
*'''Lymphadenopathy'''
** '''Enlarged hilar or retroperitoneal lymph nodes (≥2 cm) on CT almost always harbor malignancy, but this should be confirmed by surgical exploration or percutaneous biopsy if the patient is not a surgical candidate.'''
** '''Many smaller nodes prove to be inflammatory rather than neoplastic and should not preclude surgical therapy'''

*
{| class="wikitable"
|+Left, endophytic, renal mass on contrast-enhanced CT scan in a 45-year old male. Radical nephrectomy pathology demonstrated pT2a, clear cell renal cell carcinoma
![[File:Kidney CT Mass Axial.png|frameless|592x592px]]
![[File:Kidney CT Mass Sagittal.png|none|thumb|655x655px]]
|-
|Axial view
|Sagittal view
|}