Breast calcifications

Breast calcifications are are deposits of calcium salts in the breast, which are radio-opaque on mammography. The majority are benign, but they can be associated with cancer. The ability to diagnose and appropriately manage the significant microcalcifications and differentiate them from innocuous findings is part of the art and science of breast imaging.

Epidemiology

Calcifications are extremely common, present in ~85% of mammograms ⁸. Their frequency increases with age. 

In a screening mammography program, the rate of recall because of calcifications was 1.7% and of these, 19% resulted in a cancer diagnosis ¹³. In the digital mammography era, about one-sixth of all recalls are for calcifications ¹⁵.

Calcification-specific cancer detection rates in the era of digital mammography range from 1.9 to 3.2 in 1000 screened ^13,14. A third of breast cancers show calcifications as the only mammographically suspicious feature ¹³. Up to 50% of breast cancers can be associated with calcification while 15-30% of calcifications biopsied for various reasons tend to be malignant in asymptomatic patients ¹⁰.

Pathology

Etiology

Of the breast cancers detected on mammography due to calcifications, about two-thirds represent ductal carcinoma in situ and the remainder are invasive ductal carcinoma ^13,14. In contrast, the causes of benign calcifications are broad and covered in detail in other sections (Radiographic features and Differential diagnosis).

Microscopic appearance

Calcifications typically represent calcium phosphate or calcium oxalate salt deposition. The former appear purple on hematoxylin and eosin stain, while the latter requires the use of polarized light to assess birefringence.

Radiographic features

The BI-RADS lexicon lexicon prescribes descriptors for typically benign calcifications as well as suspicious morphologic terms and descriptors of calcification distribution¹⁷. See also the separate article on breast calcifications: an approach.

Typically benign calcifications

• skin: they have a very fine lucent centre; they are seen incentered, usually tightly grouped, and can be localized on tangential views if the skin line onappearance is atypical; formed within the edge of the breast and are very small punctate calcifications in the skin poresdermis/epidermis
• vascular: when extensive they are easy to pick up parallel tram tracks or discontinuous linear appearance at the margins of a tubular structure; when they are just isolatedformed in oneblood vessel they can potentially be confused with DCIS; the vessel has two walls and in most cases a tram line can be visualised if both walls are calcified
• coarse or "popcorn-like": large (>2-3 mm), sometimes confluent or associated with a circumscribed mass; formed in involuting fibroadenomas
• large rod-like: large tubules in a radiating and sometimes branching distribution oriented towards the nipple; with the largest in a breast measuring mean 4 mm long and 0.6 mm wide, usually bilateral, usually intraductal but sometimes periductal, usually in older women (>60 years) ¹⁸; formed within ductal ectasia
• round, including punctate: circular in morphology, small (usually <1 mm) or punctate (<0.5 mm if punctate) in size; frequently formed in acini of terminal ductal lobular unit
• rim: "eggshell", lucent centered; formed in the walls of oil cysts (fat necrosis) or simple cysts
• dystrophic: irregular, usually >1 mm; formed after radiation, trauma, or surgery
• milk of calcium: the classic "tea cups" that show acurvilinear or linear level on the mediolateral90° lateral (ML/LM) view but a smudge on the CC view view; formed as sediment within cysts
• suture: linear or tubular calcifications; formed on loops and knots of surgical sutures

Suspicious morphology of calcifications

• amorphous
• coarse heterogeneous: irregular, generally 0.5-1 mm
• amorphous: indistinct and/or small, such that another specific shape cannot be determined
• fine pleomorphic: variable shape like "shards of glass", generally <0.5 mm
• fine linear or fine-linear branching: thin (<0.5 mm), linear, branching or irregularly arranged

See also the separate article on suspicious breast calcifications. These descriptors and their associated probability of malignancy can be further modified by their distribution.

Distribution

• diffuse: may be scattered calcifications or multiple similar appearing clusters of calcifications scattered randomly throughout the breast; almost always benign
• regional: scattered in a larger volume (>2 cc) of breast tissue and not in the expected ductal distribution
• grouped: at cluster of at least 5 calcifications within 1 cm from each other, in an area at most 2 cm in greatest dimension
• linear: calcifications arrayed in a line suggestive of deposition along ducts; suspicious if there is not a characteristically benign appearance such as vascular or large rod-like calcifications)
• segmental: calcium deposits in ducts and branches of a segment or lobe; suspicious if not characteristically benign such as large rod-like

Radiology report

Calcifications that are definitely benign do not need to be reported, so that the referrer or patient reading the report would not be confused reading the report, but they may be reported if there is concern that other observers might not interpret them as benign ¹⁷.

Round calcifications are benign (BI-RADS 2) if diffuse or stable for several years. Grouped round calcifications in isolation are probably benign (BI-RADS 3). Round calcifications that are new, increase, or linear or segmental in distribution are suspicious (BI-RADS 4).

Amorphous calcifications are suspicious (BI-RADS 4) unless they are bilateral and diffuse and/or stable for many years.

Differential diagnosis

There are many etiologies of breast calcifications.

Ductal calcifications may represent either the calcifications of DCIS or casting calcifications in a duct

• fat necrosis
• malignancy
  • intraductal calcification
  • psammomatous calcification from mucin producing tumourstumors
• fibrocystic change
  • liponecrosis microcystica
  • from an oil cyst
• secretary calcification:plasma cell mastitis
• degenerating fibroadenoma
• underlying metabolic abnormality
  • tumoral calcification within breast
  • dystrophic calcification within the breast
• parasitic infestations
  • loaisis of the breast
  • trichinosis of the breast

See also

• breast calcifications: an approach
• suspicious breast calcifications