A spot compression mammogram (SCM) is a specialized, focused imaging technique used when an initial screening mammogram identifies an area requiring closer investigation. The SCM is a non-invasive diagnostic tool intended to clarify an ambiguous finding, allowing the radiologist to obtain a highly detailed image of a small, targeted region of the breast tissue.
The Shift from Screening to Diagnostic Imaging
The initial screening mammogram is a general overview designed to detect potential abnormalities across the entire breast tissue. This standard screening typically captures two views of each breast. However, this broad imaging means that normal, overlapping breast tissue can sometimes create a false appearance of a mass or density.
When the screening image shows an indistinct area obscured by tissue overlap, the clinical intent shifts from screening to diagnosis. The diagnostic mammogram, which includes the SCM, is a targeted investigation performed under the supervision of a radiologist. The purpose of this immediate follow-up is to determine if the unclear finding represents a true abnormality or simply a summation artifact of normal structures. This targeted approach allows for a definitive assessment.
How Spot Compression Isolates Tissue
The physical procedure of a spot compression mammogram differs significantly from the full-field compression used during a routine screening scan. Instead of the large paddle that compresses the entire breast, the technologist uses a smaller, specialized compression paddle. These spot paddles are typically around 5 centimeters in diameter and are designed to focus pressure on the suspicious area.
Applying this localized pressure serves to improve image quality. The focused force effectively separates and spreads out the surrounding breast tissue, which eliminates the possibility of a “pseudolesion” caused by the superimposition of normal structures. This separation is necessary for a clear view of the area of concern.
Furthermore, the increased compression reduces the thickness of the targeted tissue, which helps immobilize the area and minimizes blurring. The reduced thickness also brings the area of interest closer to the detector plate. This proximity results in a higher-resolution image, often combined with a magnification view, allowing the radiologist to see fine details not visible on the initial screening image.
Clarifying Specific Areas of Concern
The SCM clarifies three main types of ambiguous findings that appear on a screening mammogram, each requiring a precise, high-resolution assessment. For suspected masses or nodules, the SCM helps determine the true nature of the finding by clearly defining its margins. The localized compression allows the radiologist to observe whether borders are smooth and well-defined (suggesting a benign cyst or lymph node), or irregular and spiculated (a more concerning feature).
The procedure is also used to investigate architectural distortion, defined as a disruption of the normal structure of breast tissue without a clear mass. The SCM confirms if the tissue is genuinely pulled or retracted, which can be an early sign of malignancy, or if the initial view was simply an awkward compression of normal fibers. If the apparent distortion disperses under the focused compression, it is likely a benign finding.
The third application is resolving asymmetries or focal densities, where an area appears unusually dense in one breast or one view. In most cases, the SCM’s focused pressure disperses this density, confirming it was merely normal glandular tissue bunched together. If the density persists and remains visible under the localized compression, it is classified as a true focal density requiring further diagnostic workup.
Understanding Your Results and Follow Up
Because the spot compression mammogram is a diagnostic procedure, the images are usually reviewed by the radiologist immediately after they are taken. The radiologist uses the Breast Imaging Reporting and Data System (BI-RADS) to communicate the findings. This system uses categories from 0 to 6 to suggest the appropriate next steps.
The goal of the SCM is to move a finding from a BI-RADS Category 0, which indicates the image is incomplete and needs additional evaluation, to a definitive category. If focused views confirm the finding is benign, such as normal tissue overlap, Category 2 is assigned, meaning no further action is necessary beyond routine screening. Category 3 is used if the finding is likely benign but requires a short-term check, recommending a follow-up scan in six months to ensure stability. If the SCM confirms a persistent, suspicious feature, Category 4 or 5 is assigned, which may lead to a recommendation for further imaging, such as an ultrasound, or a biopsy for definitive tissue sampling.