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Workup of an Asymmetric Density on Mammography
Written by: Ellen
Shaw de Paredes, MD
June 12, 2001
Asymmetry on mammography is a common finding and most often represents
benign glandular tissue. However, one subtle sign of malignancy is
an asymmetric density, and the correct identification of these lesions
is of paramount importance.
The ACR BIRADS™ Lexicon (1) describes four types of non-mass
densities as follows:
- asymmetric breast tissue,
- focal asymmetric density,
- a density seen in one projection,
- architectural distortion.
A focal asymmetric density is seen on two views, but does not have
the prominent margins of a mass. A density seen in one projection
may be a true lesion or may be superimposed tissue, and additional
views are necessary to determine this. Architectural distortion
is focal spiculation without a central tumor density. Without an
explanation for a benign etiology (i.e. a post-surgical scar), architectural
distortion is a worrisome finding that requires biopsy.
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Table 1
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Etiologies of Focal Asymmetric Density
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•Asymmetric glandular tissue |
| •Fibrocystic change, fibrosis, adenosis, sclerosing
adenosis, cyst |
| •Post traumatic change, scar, fat necrosis |
| •Hormone-sensitive parenchyma |
| •Hematoma |
| •Diabetic fibrous mastopathy |
| •Invasive ductal carcinoma |
| •Invasive lobular carcinoma |
| •Lymphoma |
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Table 2
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Etiologies of Architectural Distortion
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•Post surgical scar/fat necrosis |
| •Radial scar |
| •Sclerosing adenosis |
| •Carcinoma (invasive lobular, tubular, invasive ductal) |
Areas of asymmetric density of greatest concern, and for which
biopsy is recommended, include the following:
- developing asymmetric density,
- palpable asymmetry,
- associated microcalcifications,
- associated architectural distortion.
In patients who have been placed on hormone replacement therapy
since the prior mammogram, and in whom there is evidence of a new
focal asymmetric density, discontinuation of the hormones for a
short period (3-4 weeks) followed by repeat mammography may reveal
that the abnormal finding has disappeared. Persistent new asymmetry
after discontinuation of hormones should prompt further investigation
with biopsy.
Clinical examination and ultrasound are important adjuncts in the
evaluation of focal asymmetry. A corresponding palpable mass or
a sonographically suspicious finding such as a solid mass or shadowing
(Figure
1), warrants tissue sampling.
Types of cancers that may present as areas of focal asymmetric
density or architectural distortion (Figure
2) include invasive ductal, or invasive lobular carcinoma and
tubular carcinoma. In particular, invasive lobular cancer can be
very subtle on mammography, appearing as an area of asymmetric density
or distortion.
References:
- Kopans DD, Swann CA, White G, McCarthy KA,
Hall DA, Belmonte SJ, Gallagher W. Asymmetric
breast tissue, Radiology 1989; 171:639-43.
- D’Orsi C, Bassett L, et al. Breast
Imaging Reporting and Data System. 3rd Edition,
American College of Radiology, 1998.
- Helvie MA, Paramagul C, Oberman HA, Adler
DD. Invasive
lobular carcinoma: Imaging features and clinical detection.
Invest Radiol. 1993; 28:202-7.
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