Differential Diagnosis for Mammography in Malignancy vs Fat Necrosis

When differentiating between malignancy and fat necrosis on mammography, several features and diagnoses must be considered. The following categorization helps in organizing the thought process:

• Single Most Likely Diagnosis
  • Invasive Ductal Carcinoma: This is the most common type of breast cancer and can present with a variety of mammographic findings, including irregular masses, spiculations, and architectural distortions. The presence of these features, especially if new or changing, would make malignancy a top consideration.
• Other Likely Diagnoses
  • Fat Necrosis: This condition can mimic malignancy on mammography, presenting with irregular masses or calcifications. It often occurs after trauma or surgery and can be confirmed with a history of such events or by the presence of characteristic "eggshell" calcifications around a lucent center.
  • Ductal Carcinoma In Situ (DCIS): DCIS can present with microcalcifications on mammography, which may be clustered, linear, or segmental in distribution. The appearance and distribution of these calcifications can help differentiate DCIS from benign entities.
• Do Not Miss Diagnoses
  • Inflammatory Breast Cancer: Although less common, inflammatory breast cancer is aggressive and can present with skin thickening, edema, and increased density on mammography, mimicking fat necrosis or other benign conditions. Its rapid progression and poor prognosis make it a "do not miss" diagnosis.
  • Lymphoma: Primary breast lymphoma is rare but can present with a rapidly growing mass. On mammography, it may appear as a large, dense mass, potentially mimicking other malignancies or fat necrosis.
• Rare Diagnoses
  • Pseudoangiomatous Stromal Hyperplasia (PASH): A rare benign condition that can mimic malignancy on imaging due to its ability to form masses. It is more commonly seen in younger women.
  • Hamartoma: A benign tumor of the breast that can contain both fatty and dense tissue, sometimes mimicking fat necrosis or malignancy on mammography due to its variable appearance.

Each diagnosis is considered based on the specific mammographic features, clinical history, and the potential consequences of missing a diagnosis. The use of additional imaging modalities, such as ultrasound or MRI, and biopsy may be necessary to confirm the diagnosis.