Diagnostic ultrasound ( PDFDrive )

342 PART II Abdominal and Pelvic Sonography
A B C
D
E
F
G H I
FIG. 9.47 Sonographic Appearances of Renal Cell Carcinoma on Sagittal Sonograms. (A) Tiny incidental hypoechoic tumor. (B) Exophytic
echogenic upper-pole tumor with peripheral cystic spaces and larger uniform echogenic lower-pole tumor in same patient. (C) Small echogenic
nodule simulating an angiomyolipoma. (D) Exophytic echogenic midpole renal mass. (E) Exophytic hypoechoic upper-pole renal mass. (F) Large
central renal sinus mass with no associated caliectasis. (G) Large solid heterogeneous mass in the lower pole of the kidney compressing the renal
pelvis with upper-pole caliectasis. (H) Large iniltrative renal mass with maintenance of reniform shape. (I) Large upper-pole cystic mass showing
numerous thick internal septations. See also Video 9.2.
renal parenchyma; Forman et al. 149 found that 77% of smaller
RCCs were echogenic, and Yamashita et al. 150,151 reported 61%
as echogenic.
he small, echogenic RCC may be diicult to diferentiate
from a benign angiomyolipoma (AML) at ultrasound. Yamashita
et al. 151 emphasized the overlap in RCC/AML imaging appearance.
A thin, hypoechoic rim, thought to be a pseudocapsule at histology,
was reported in 84% of RCCs and no AMLs. Weak shadowing
posterior to AMLs and hypoechoic halos or cystic spaces in
RCCs were also thought to be characteristic features. 152 Nonetheless,
although increased echogenicity of a solid renal lesion has
high sensitivity for AML (99%), it is not speciic. If a lesion is
of a size that would lead to a change in management, echogenic
renal lesions should be further assessed with either MRI or CT. 153
he exact pathologic basis for the hyperechoic appearance
of RCC is not understood, but increased echogenicity has
been reported in RCCs with papillary, tubular, or microcystic
architecture and in tumors with minute calciication, necrosis,
cystic degeneration, or ibrosis. 131 Macroscopic calciication
are identiied in 8% to 18% of RCCs. his calciication may be
punctate, curvilinear, difuse (rare), central, or peripheral. 154-158
Daniel et al. 157 showed that central calciication was associated with
a malignant tumor in 87% of cases. When posterior rim shadowing
or difuse calciication make it impossible to characterize a
renal lesion by ultrasound, CT is needed to identify additional
features of malignancy (e.g., enhancement of associated sot
tissue mass). 159
Papillary tumors account for 15% of all RCCs. 129,160 he
papillary type is characterized by slower growth, a lower stage at
presentation, and a better prognosis. 161 Papillary tumors also tend
to be hypoechoic or isoechoic, although no consistent sonographic
pattern exists, because some may also be hyperechoic. 160