Chromophobe renal cell carcinoma (chRCC) is a subtype of renal cell carcinoma originating from intercalated cells of the collecting duct system (cortical portion), accounting for approximately 5-7% of all kidney cancers. Histologically composed of large, pale cells with reticular cytoplasm and prominent cell membranes ('plant cell' appearance). Typically occurs between ages 40-70 with a slight female predominance. Has a significantly better prognosis compared to clear cell RCC, with 5-year survival rates exceeding 80-90%. On imaging, it presents as a homogeneous, well-defined, moderately enhancing solid mass. The most important imaging feature is the 'spoke-wheel' enhancement pattern after contrast administration and a central stellate scar. Differentiation from oncocytoma on imaging is extremely difficult; definitive diagnosis usually requires histopathological examination. Strongly associated with Birt-Hogg-Dubé syndrome. Partial nephrectomy is the preferred treatment; metastatic disease is rare.
Age Range
40-75
Peak Age
58
Gender
Equal
Prevalence
Uncommon
Chromophobe RCC originates from intercalated cells (type B intercalated cells, cortical collecting duct) in the distal portion of the nephron. This origin explains the tumor's different biological behavior compared to clear cell RCC (proximal tubule origin). Genetically, the most common alteration is complete loss of multiple chromosomes (1, 2, 6, 10, 13, 17, 21) — this differs from other RCC subtypes and constitutes the diagnostic genetic signature. TP53 and PTEN mutations are frequent. VEGF (vascular endothelial growth factor) expression is markedly lower compared to clear cell RCC; therefore the tumor is hypovascular or moderately vascular, without prominent hypervascularity. The tumor generally remains well-circumscribed and encapsulated even when reaching large sizes. The central stellate scar reflects fibrous tissue and degeneration in the tumor center. Due to low vascularity, necrosis and hemorrhage are less common compared to clear cell RCC. The shared cellular origin with oncocytoma (both from the distal nephron) makes differentiation difficult on imaging and sometimes even histologically. In Birt-Hogg-Dubé syndrome patients (FLCN gene mutation), chromophobe RCC and oncocytoma hybrid tumors are seen with increased frequency.
Spoke-wheel-like enhancement pattern formed by vascular structures extending radially from the tumor center to the periphery in the arterial phase. This pattern reflects the tumor's organized vascular architecture branching radially from a single central feeding artery. It differs from the chaotic hypervascularity of clear cell RCC and hypovascularity of papillary RCC. Not pathognomonic as a similar pattern can be seen in oncocytoma, but it strongly supports these two diagnoses.
Characteristic 'spoke-wheel' enhancement pattern in the arterial (corticomedullary) phase with radial vascular structures extending from center to periphery. Enhancement is less intense compared to clear cell RCC but more prominent than papillary RCC. The tumor generally shows density close to or slightly below the renal cortex. This pattern reflects the radially distributed vascular network from the central feeding artery of the tumor. Smaller tumors (<4 cm) may show more homogeneous enhancement; the spoke-wheel pattern becomes more apparent in larger tumors.
Report Sentence
Well-defined solid mass in the kidney demonstrating a 'spoke-wheel' enhancement pattern with radial vascular structures extending from center to periphery in the arterial phase; chromophobe renal cell carcinoma or oncocytoma should be considered as leading diagnoses.
In the nephrographic phase, the tumor shows homogeneous, moderate enhancement. Unlike the prominent hypervascular enhancement of clear cell RCC, enhancement in chromophobe RCC is more temperate (typically 40-80 HU increase). Importantly, tumor density in the nephrographic phase remains lower than the renal cortex but higher than papillary RCC. The homogeneity of enhancement reflects the tumor's organized vascular structure and rarity of necrosis/hemorrhage. This phase best evaluates the solid nature of the tumor, and the absence of cystic components is notable.
Report Sentence
Solid mass in the kidney demonstrating homogeneous, moderate enhancement in the nephrographic phase with density lower than renal cortex; the enhancement pattern is compatible with chromophobe RCC or oncocytoma.
On non-contrast CT, a hypodense stellate (star-shaped) scar may be seen in the tumor center. This scar represents the fibrous center of the tumor and is generally more apparent in larger tumors (>5 cm). On non-contrast CT, the scar shows lower density than the tumor parenchyma (fibrous tissue and microcystic degeneration). On contrast-enhanced series, the scar may show mild delayed enhancement (delayed contrast uptake by fibrous tissue). The presence of a central scar can be conceptualized as the renal analogue of FNH (focal nodular hyperplasia — liver); however, in the kidney it can be seen in both oncocytoma and chromophobe RCC.
Report Sentence
Hypodense area in stellate configuration is seen in the center of the solid renal mass; this finding is compatible with a central scar and should be evaluated for chromophobe RCC or oncocytoma.
The segmental enhancement inversion sign is a CT finding proposed to differentiate chromophobe RCC from oncocytoma. In the arterial phase, certain segments of the tumor enhance more intensely than the renal cortex, while in the nephrographic phase, the enhancement intensity of the same segments reverses and remains lower than the cortex. This 'inversion' pattern is less prominent in oncocytoma. The finding reflects the tumor's heterogeneous vascular structure — some segments have richer arterial supply while overall vascular density is lower than normal parenchyma. However, the sensitivity and specificity of this sign alone are not sufficient; histopathological confirmation is required.
Report Sentence
Segmental enhancement inversion is observed in the solid renal mass with segments that enhanced more than cortex in arterial phase dropping below cortex in nephrographic phase; this finding may favor chromophobe RCC.
On T2-weighted images, chromophobe RCC typically shows homogeneous low-to-intermediate signal intensity. This feature differs from the typical T2 hyperintense signal of clear cell RCC. The low T2 signal reflects the tumor's dense cellular structure and low water content. The central stellate scar appears T2 hyperintense and is clearly distinguished from surrounding tumor tissue — this contrast results from the long T2 relaxation time of free water molecules in the fibrous/microcystic structure of the scar. The combination of homogeneous low-to-intermediate T2 signal + central T2 hyperintense scar is quite typical for chromophobe RCC.
Report Sentence
The solid renal mass shows homogeneous low-to-intermediate signal intensity on T2-weighted sequences; a T2 hyperintense area compatible with a stellate scar is seen in the central region. These findings are compatible with chromophobe RCC or oncocytoma.
On T1-weighted images, chromophobe RCC typically shows homogeneous isointense or mildly hypointense signal relative to renal parenchyma. T1 hyperintense areas due to hemorrhagic components frequently seen in clear cell RCC are rare in chromophobe RCC. The central scar is usually T1 hypointense. Homogeneous T1 signal supports the tumor's homogeneous structure and absence of necrosis/hemorrhage. No significant signal drop is expected on opposed-phase sequences — intracellular lipid accumulation in chromophobe RCC is much less than in clear cell RCC.
Report Sentence
The solid renal mass shows homogeneous isointense signal relative to renal parenchyma on T1-weighted sequences; no significant signal drop is observed on opposed-phase sequences.
On diffusion-weighted imaging (DWI), chromophobe RCC shows moderate diffusion restriction — mild-to-moderate hyperintense signal at high b-value (b=800-1000) and moderately low signal on ADC map. ADC values are generally lower than clear cell RCC but higher than papillary RCC (typical ADC: 1.2-1.6 × 10⁻³ mm²/s). This feature reflects the tumor's dense cellular structure. Diffusion restriction is more prominent compared to clear cell RCC because chromophobe RCC cells are larger and more tightly packed. The homogeneous diffusion restriction pattern is consistent with the tumor's homogeneous structure.
Report Sentence
The solid renal mass demonstrates moderate diffusion restriction on diffusion-weighted imaging (ADC values lower than renal cortex).
On B-mode ultrasonography, chromophobe RCC typically appears as a well-defined, homogeneous, iso-to-hypoechoic solid mass. More homogeneous echo texture compared to clear cell RCC is notable. The mass usually slightly protrudes beyond the renal contour. Calcification or cystic components in the internal structure are rare. The central scar may be seen as a hypoechoic area on ultrasound but is generally indistinguishable in small tumors. On Doppler ultrasound, moderate vascularity is observed within the tumor; the spoke-wheel vascular pattern may sometimes be visualized on color Doppler but is not as reliable as CT/MRI.
Report Sentence
A well-defined, homogeneous, iso-to-hypoechoic solid mass is seen in the kidney; moderate vascularity is present on Doppler examination.
Criteria
Most common form (70-80%). Large cells with pale cytoplasm, prominent cell membranes, perinuclear halo (koilocyte-like). Cytoplasm stains positively with Hale's colloidal iron stain.
Distinct Features
On imaging, generally more homogeneous enhancement, regular margins, central scar more prominent. Excellent prognosis — 5-year disease-specific survival above 95%. Metastasis very rare (2-5%).
Criteria
20-30% of all chromophobe RCCs. Dense eosinophilic (granular) cytoplasm, smaller cells, histologically very similar to oncocytoma. CK7 immunohistochemistry and genetic analysis required for differentiation from oncocytoma.
Distinct Features
Differentiation from classic type on imaging is generally not possible. Histological overlap with oncocytoma is most frequent in this subtype. This variant and hybrid tumors are frequently seen in BHD syndrome. Prognosis similar to classic variant.
Criteria
Rare variant (5-8%). Presence of spindle cell (sarcomatoid) component within the tumor. In the WHO classification, this is a high-grade degeneration that can occur in any RCC subtype — not a separate histological subtype but a prognostic indicator.
Distinct Features
On imaging, heterogeneous enhancement, irregular margins, necrotic areas — significant difference from the classic homogeneous chromophobe RCC appearance. Exhibits invasive behavior: perinephric fat invasion, renal vein involvement, local spread. Prognosis is significantly worse — metastatic disease frequency exceeds 50%. Requires surgery + systemic treatment.
Criteria
Tumor carrying features of both oncocytoma and chromophobe RCC, particularly seen in Birt-Hogg-Dubé (BHD) syndrome. More than 50% of renal tumors in BHD patients are hybrid tumors. Associated with FLCN (folliculin) gene mutation.
Distinct Features
Cannot be distinguished from oncocytoma or chromophobe RCC on imaging. BHD syndrome should be considered with bilateral, multifocal renal tumors. Skin fibrofolliculomas and pulmonary cysts may be associated. Good prognosis — considered benign/low malignant potential. Nephron-sparing surgery (partial nephrectomy) preferred.
Distinguishing Feature
Most challenging differential — reliable differentiation on imaging is often not possible. Both tumors may show spoke-wheel enhancement, central scar, and homogeneous moderate enhancement. Segmental enhancement inversion sign has been more frequently described in chromophobe RCC. Oncocytoma tends to show slightly more intense enhancement than chromophobe RCC in the nephrographic phase. Definitive differentiation usually requires biopsy or surgical pathology (CK7 positivity and chromosomal losses support chromophobe RCC).
Distinguishing Feature
Clear cell RCC shows prominent hypervascular enhancement in arterial phase (>100 HU increase) and is usually heterogeneous (necrosis/hemorrhage). Enhancement in chromophobe RCC is more temperate and homogeneous. On MRI, clear cell RCC shows signal drop on opposed-phase (intracellular lipid) and is T2 hyperintense; chromophobe RCC lacks opposed-phase signal drop and shows low-to-intermediate T2 signal. Clear cell RCC more commonly demonstrates renal vein thrombosis.
Distinguishing Feature
Papillary RCC is typically hypovascular — minimal enhancement in arterial phase with progressive (increasing) enhancement pattern. Chromophobe RCC shows more enhancement. On MRI, papillary RCC is markedly T2 hypointense (lower signal than chromophobe RCC) and may be T1 hyperintense due to hemorrhagic component. Papillary RCC is typically detected at smaller size, may be bilateral/multifocal, and has a homogeneous encapsulated appearance.
Distinguishing Feature
Fat-poor angiomyolipoma (AML) can present as a homogeneous, solid, hypoechoic/hypodense mass and may mimic chromophobe RCC. MRI is important for differentiation: fat-poor AML shows markedly T2 hypointense signal (lower than chromophobe RCC — due to smooth muscle component within the tumor). Minimal microscopic fat may be detected on chemical shift sequences in fat-poor AML. On CT, fat-poor AML may show homogeneous, intense enhancement. Size is typically <3 cm. Definitive differentiation may require biopsy.
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
6-monthChromophobe RCC has one of the best prognoses among RCC subtypes. 5-year disease-specific survival exceeds 90% and metastasis rate is low (2-5% in classic type). Nephron-sparing surgery (partial nephrectomy) is preferred for treatment; partial nephrectomy is the standard approach especially in T1a-T1b stage tumors <7 cm. Since reliable differentiation from oncocytoma on imaging is not possible, renal mass biopsy (fine needle aspiration or core biopsy) can clarify the diagnosis in suspicious cases — if definitive oncocytoma diagnosis is made, active surveillance becomes an option. FLCN gene testing is recommended when Birt-Hogg-Dubé syndrome is suspected (bilateral/multifocal tumors, family history, skin lesions, pulmonary cysts). Post-operative follow-up with abdominal CT or MRI every 6 months for the first 2 years, then annually is recommended. Prognosis worsens significantly with sarcomatoid transformation and adjuvant therapy should be considered.
Chromophobe RCC has better prognosis than other RCC subtypes (5-year survival >90%). Metastasis rate is low. Surgical resection (partial nephrectomy) is curative. May be associated with Birt-Hogg-Dube syndrome.