Breast masses

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Invasive Lobular Carcinoma (ILC)

  • Infiltrated breast like spiderweb causing thickening without central mass
  • More difficult to detect
  • 6-9% of breast cancer
  • Shrinking breast appearance on mammogram due to loss of elasticity
  • Differential includes radial sclerosis (radial scar)
  • Ultimately need surgical excision, but core biopsy may aid in sugical planning

Invasive ductal carcinoma Not Otherwise Specified (IDC NOS)

  • IDC NOS and Ductal carcinoma in situ (DCIS) account for 85% of breast cancers
  • IDC NOS presents as a spiculated or irregular mass or as a new focal asymmetry

Well Differentiated Subtypes of IDC

  • Overall better prognosis than IDC NOS
  • Mucinous
    • Low density oval, circumscribed mass containing mucin
    • High T2 signal on MRI
  • Medullary
    • Round mass with ill defined boarders
    • Well circumscribed carcinoma composed of poorly differentiated cells with scant stroma and prominent lymphoid infiltration
  • Tubular
    • Appears spiculated
    • Excellent prognosis (tubular = cool)
    • Can be slow growing
  • Papillary
    • Round intraductal or intracystic mass
    • Often present with nipple discharge
    • Cannot differentiate papilloma from papillary carcinoma on imaging alone

Peanut M&Ms - Papillary, Medullary and Mucinous are all round on Mammo/US

Cancers of Stromal Origin

  • Phyllodes
    • Mimics fibroadenoma, except on US with ill defined margins
    • Large in size (>3cm)
    • Middle-aged and older women
  • Angiosarcoma
    • Ill defined vascular mass
    • Can be secondary to radiation therapy
  • Osteosarcoma - calcified mass
  • Adenoid Cystic Carcinoma - arises from secretory glands


  • Most common are: lymphoma, melanoma, rhabdomyosarcoma, lung, ovarian, renal cell, cervical

Unusual Breast Cancers: Useful Clues to Expanding the Differential Diagnosis