Diagnostic ultrasound ( PDFDrive )

CHAPTER 21 The Breast 775
FIG. 21.20 Simple Cysts. Simple cysts are anechoic and have
enhanced sound transmission, well-circumscribed borders, thin-edge
shadows, and thin, echogenic walls. They are benign (Breast Imaging
Reporting and Data System [BI-RADS] 2) and require no aspiration or
follow-up. See also Video 21.3.
Complicated Cysts
Complicated cysts are cysts that contain debris. his manifests
as echogenic luid, luid-debris levels, or fat-luid levels without
a solid vascular component. Cellular debris, epithelial cells, blood,
proteinaceous material, and pus can all contribute to the appearance
of low-level echoes within a complicated cyst. Complicated
cysts are generally benign as part of the broad spectrum of benign
ibrocystic change, but have a low risk of containing papillomas
or carcinomas 46 and are therefore oten classiied as BI-RADS
3, for which follow-up is recommended.
here are some instances in which complicated cysts can be
characterized as BI-RADS 2. his is the case when the complicated
cyst can conidently be characterized as a speciic benign lesion
such as a galactocele (which is a cyst that contains milk and
oten demonstrates a fat-luid level on ultrasound) or a cyst of
skin origin such as an epidermal inclusion cyst.
Cysts can contain particles suspended in luid that are so light
that they can be moved by the energy of the B-mode imaging
or color or power Doppler ultrasound beam. Such particles are
subcellular in size and are oten seen with uncomplicated FCC.
In general, high-transmit power settings are necessary to cause
such particles to move during real-time B-mode imaging.
However, the energy of the color or power Doppler ultrasound
beam is high enough to cause these particles to move at even
default low-power settings, creating what has been termed “color
streaking.” Particles are forced posteriorly by the energy of the
Doppler ultrasound beam, creating vertically oriented color
streaks within the cyst as they move (Fig. 21.21). he particles
that cause color streaking have been shown to be cholesterol
crystals, which can be seen on cytologic evaluation as birefractive
crystals when viewed with polarized light.
Milk of calcium is a BI-RADS 2 mammographic inding that
has been directly applied to sonography. Milk of calcium is a
collection of tiny calculi within the lumen of a cyst. Such calculi
are very common in benign FCC and can be demonstrated
deinitively on horizontal beam mammographic ilms. Sonography
can prove the presence of milk of calcium by demonstrating that
the calciications move within the cyst to new dependent positions
created by lateral decubitus or upright positioning of the patient
(Fig. 21.22). Although mammography can generally show smaller
and more numerous calciications, sonography has one advantage
over mammography in demonstrating milk of calcium. Mammography
requires dozens of small calciications before the classic
“teacup” appearance can be shown on horizontal beam ilms,
whereas sonography can deinitively demonstrate a single mobile
calculus in a cyst (Fig. 21.23). hus, although less sensitive than
mammography for calciications, sonography can be more speciic
than mammography for milk of calcium. his is particularly
true when mammography shows a nonspeciic cluster of punctate
microcalciications that might require biopsy, but sonography
shows benign clustered microcysts, each containing one or more
tiny calculi (Fig. 21.24).
Fat-luid levels within cysts are deinitively benign mammographic
indings that have been directly applied to ultrasound.
Fat-luid levels are rarely demonstrated on mammography, and
usually only within classic galactoceles, but are much more
frequently demonstrated by sonography. he lipid layer appears
echogenic compared with cyst luid and loats on the luid in
the nondependent portion of the cyst. he lipid layer moves
within the cyst to a new nondependent position with change in
the patient’s position from supine to lateral decubitus or upright
(Fig. 21.25). As with tumefactive sludge, lipid layers tend to shit
very slowly within a cyst when the patient’s position is changed,
requiring up to 5 minutes to document the shit of a fat-luid
level. During the shit in position, the shape of the interface
between the lipid and luid layers changes and is usually obliquely
oriented with respect to the tabletop and has a sigmoid shape.
he oblique orientation of the interface in combination with the
sigmoid shape is characteristic of a fat-luid level in the process
of equilibrating to a new position and may represent a shortcut
to waiting 5 minutes for the fat-luid level to shit. Power Doppler
ultrasound fremitus can also be used to distinguish a mural
nodule from a fat-luid level. 47 he lipid layer is not attached to
the cyst wall, so the fremitus artifact will not pass through it.
On the other hand, true papillary lesions that are attached to
the cyst wall will vibrate and transmit the fremitus artifact on
power Doppler; having the patient hum in a deep voice creates
an orange artifact on power Doppler ultrasound (Fig. 21.26).
Lipid cysts or oil cysts are deinitively benign mammographic
indings. Unfortunately, lipid cysts usually appear more deinitively
benign on mammography than sonography. Most lipid cysts
lack enhanced sound transmission and may actually have posterior
shadowing due to calciied walls. Most have some additional
suspicious features on sonography, such as (1) mural nodules;
(2) thick septations; (3) thick walls; and (4) luid debris levels
(Fig. 21.27). his should not be surprising because most lipid