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Case number:	140
Age:	43
Clinical presentation:	Premenopausal woman with average risk of breast cancer presented with a lump in the left breast of recent onset. Examination revealed a left upper quadrant lump. She has had a stable right breast lump for many years, which is proven fibroadenoma on tissue diagnosis.

Mammography:

Breast composition:	ACR category d (the breasts are extremely dense, which lowers the sensitivity of mammography)
Mammography features:
‣ Location of the lesion:	Left breast, upper inner quadrant at 10–11 o’clock, middle third
‣ Mass:
• Number:	1
• Size:	4.2 × 4.0 cm
• Shape:	Oval
• Margins:	Circumscribed
• Density:	Equal
‣ Calcifications:
• Typically benign:	None
• Suspicious:	None
• Distribution:	None
‣ Architectural distortion:	None
‣ Asymmetry:	None
‣ Intramammary node:	None
‣ Skin lesion:	None
‣ Solitary dilated duct:	None
‣ Associated features:	None

Breast composition:	ACR category d (the breasts are extremely dense, which lowers the sensitivity of mammography)
Mammography features:
‣ Location of the lesion:	Right breast, upper inner quadrant at 1 o’clock, middle third
‣ Mass:
• Number:	1
• Size:	No
• Shape:	None
• Margins:	None
• Density:	None
‣ Calcifications:
• Typically benign:	Coarse, popcorn-like
• Suspicious:	None
• Distribution:	None
‣ Architectural distortion:	None
‣ Asymmetry:	None
‣ Intramammary node:	None
‣ Skin lesion:	None
‣ Solitary dilated duct:	None
‣ Associated features:	None

Ultrasound:

Ultrasound features: Left breast, upper inner quadrant at 11 o’clock
‣ Mass
• Location:	Left breast, upper inner quadrant at 11 o’clock
• Number:	1
• Size:	3.5 × 2.5 cm
• Shape:	Oval
• Orientation:	Parallel
• Margins:	Circumscribed
• Echo pattern:	Anechoic
• Posterior features:	Posterior shadowing
‣ Calcifications:	None
‣ Associated features:	None
‣ Special cases:	Simple cyst

Ultrasound features: Right breast, upper inner quadrant at 1 o’clock
‣ Mass
• Location:	Right breast, upper inner quadrant at 1 o’clock
• Number:	1
• Size:	1.4 × 1.2 cm
• Shape:	Oval
• Orientation:	Parallel
• Margins:	Circumscribed
• Echo pattern:	Hypoechoic
• Posterior features:	No posterior features
‣ Calcifications:	Macrocalcifications in mass
‣ Associated features:	Poor vascularity
‣ Special cases:	None

BI-RADS:

BI-RADS Category: 2 (benign)

Further assessment:

Further assessment advised: Referral for cytology

Cytology:

Cytology features:
‣ Type of sample:	FNAC
‣ Site of biopsy:
• Laterality:	Right
• Quadrant:	Lower outer
• Localization technique:	Palpation
• Nature of aspirate:	Whitish
‣ Cytological description:	Highly cellular aspirate, showing many cohesive groups of ductal cells with sharply demarcated borders with branching glove-like or “antler-horn” shapes. Many stripped or bare nuclei are seen in the background
‣ Reporting category:	Benign
‣ Diagnosis:	Fibroadenoma
‣ Comments:	None

Cytology features:
‣ Type of sample:	FNAC
‣ Site of biopsy:
• Laterality:	Left
• Quadrant:	Upper inner
• Localization technique:	Palpation
• Nature of aspirate:	0.5 mL of brownish fluid
‣ Cytological description:	Smears show foamy histiocytes on a thick proteinaceous background. Very a few ductal cells are seen
‣ Reporting category:	Benign
‣ Diagnosis:	Fibrocystic change, non-proliferative
‣ Comments:	None

Case summary:

Premenopausal woman presented with left breast lump. Diagnosed as simple cyst, BI-RADS 2 on imaging and as non-proliferative fibrocystic change on cytology. Incidentally noted right breast involuting fibroadenoma, BI-RADS 2 on imaging.

Learning points:

Cyst is the most common type of breast mass with peak incidence in women aged 30–50 years. A circumscribed mass of low or equal density on mammography and anechoic on ultrasound is diagnosed as simple cyst on imaging, BI-RADS category 2. Its natural history is to develop and regress, but occasionally it may increase in size.