Table 1.

Clinical and imaging findings of granulomatous processes of the breast and axilla

	Clinical	Imaging
Infectious	• Aspiration demonstrating bacterial, fungal or parasitic infection	• Mammo: serpiginous calcifications seen with parasitic infection • US/MRI: lymphadenopathy, skin thickening, ill-defined mass, often with sinus tracts and fistulae
Fat necrosis	• History of trauma	• Mammo: lipid cysts or dystrophic calcifications • US/MRI/CT: fat seen within the centre of mass
Suture	• Prior surgery	• Mammo: Suture knots seen on mammography
Silicone	• Breast implants	• Mammo: high-density silicone on mammography • US: snow storm on US • MRI: high-signal on silicone-sensitive sequences • CT: dual-energy CT identifying silicone
Autoimmune	• Rheumatoid: cutaneous rheumatoid nodules, RF, ANA • GPA: ANCA • Sjögren’s syndrome: dry eyes and mouth, Anti-Ro/SSA, Anti-La/SSB	• Mammo: bilateral ill-defined or irregular masses • US: Bilateral irregular hypoechoic masses
Sarcoidosis	• ACE elevated, hypercalcaemia or hypercalciuria • Lungs, skin or lymph nodes, less common eyes, liver, heart & brain	• Mammo/US: bilateral masses, asymmetry or architectural distortion • [18F]-FDG-PET: Increased uptake
IGM	• Pregnant or lactating • Subareolar or entire breast • Affected breast larger, with pain, erythema, swelling or axillary lymphadenopathy • Cultures negative	• Mammo/US: solitary mass, skin thickening and nipple retraction • MRI: marked parenchymal enhancement with sterile micro-abscesses
Lymph nodes	• Similar aetiologies to breast • Infectious vs non-infectious • Cat bite or scratch to arm	• Mammo/US: lymph nodes enlarged and round • Fistula to skin

ANA antinuclear antibody, ANCA antineutrophil cytoplasmic antibody, ACE angiotensin-converting enzyme, FDG-PET fluorodeoxyglucose positron emission tomography, GPA granulomatosis with polyangiitis, IGM idiopathic granulomatous mastitis, Mammo mammography, RF rheumatoid factor, US ultrasound