Definition
Circumscribed breast mass composed of benign stromal and epithelial cells
Alternate/Historical Names
Adult type fibroadenoma
Adenofibroma
Diagnostic Criteria
Circumscribed
Biphasic stromal and epithelial process
Intracanalicular pattern
Stroma compresses ducts into slit-like spaces
Pericanalicular pattern
Stroma surrounds round ducts
Bland, largely fibroblastic stroma
Myoepithelial cells and myofibroblasts not prominent
Hypocellular to variably hypercellular
Frequently myxoid
May be hyalinized, especially in older patients
May calcify
Rare stromal changes
Heterologous differentiation
Smooth muscle
Fat
Cartilage
Bone
Multinucleated giant cells
Ducts lined by epithelial and myoepithelial cells
Fibrocystic changes may be present
May be seen at least focally in half of cases
Areas typical of tubular adenoma may be present
Densely packed uniform round tubules
Termed "adenomatous transformation"
"Complex fibroadenoma" has been applied if any of the following are present
Cysts >3 mm diameter
Sclerosing adenosis
Epithelial calcifications
Papillary apocrine change
Atypical ductal or lobular hyperplasia may be present Carcinoma, in situ or invasive, may be present
May be lobular or ductal
Identify using standard criteria
Invasive carcinoma is present in adjacent breast in half of patients with in situ carcinoma in a fibroadenoma
Mean age of cases with carcinoma is in 40's
Necrosis may be seen rarely
More frequent in pregnancy
Giant fibroadenoma
Tumors >500 g or disproportionally large compared to rest of breast
More frequent in young and black patients
We consider the term merely descriptive
May be either adult or juvenile type
Richard L Kempson MD
Original posting:: May 27, 2006
Supplemental studies
Immunohistology
Stromal cells
CD34, Factor XIIIa positive
Smooth muscle actin typically negative to focal/weak
Differential Diagnosis
Fibroadenoma Low Grade Phyllodes Tumor
Lacks significant stromal hypercellularity
Hypercellular stroma is prominent
No stromal overgrowth
May have stromal overgrowth
No leaf-like architecture
Prominent leaf-like architecture
No condensation around ducts
Stromal condensation around ducts
Does not infiltrate
May infiltrate surrounding breast
The histologic border between these two is not always sharp
Fibroadenoma High Grade Phyllodes Tumor
Lacks significant stromal hypercellularity
Hypercellular stroma
No stromal overgrowth
Stromal overgrowth
No stromal atypia
Pleomorphic stromal cells
Stromal mitotic rate < 3/hpf
Elevated stromal mitotic rate, usually >4-5 per 10 hpf, abnormal forms may be found
Does not infiltrate
May infiltrate surrounding breast
Stromal overgrowth defined as at least one low power field (40x total magnification) composed entirely of stroma
Adenomatous Transformation of Fibroadenoma
Tubular Adenoma
Areas of typical fibroadenoma stroma
Scant stroma
Variable tubules
Uniform tubules
Areas typical of tubular adenoma may be found within fibroadenomas
Fibroadenoma Fibrocystic Disease
Discrete, circumscribed lesion
May contain poorly circumscribed areas of fibrocystic change
Fibroadenoma Mammary Hamartoma
Lobules infrequent
Lobules typically present (may be atrophic)
Frequent intracanalicular or tubular glandular proliferation
Morphologically normal ducts and lobules
Intralesional fat rare
Fat integral to lesion
Clinical
Peak age in twenties
Uncommon after menopause
Frequently smaller and hyalinized
Multiple in 25% of patients
Relative risk for development of invasive breast carcinoma
No increased risk
Non-proliferative fibrocystic change
Fibroadenoma
Solitary papilloma
Slightly increased risk (1.5 to 2 times)
Proliferative fibrocystic change
Usual ductal hyperplasia
Sclerosing adenosis (florid)
Radial scar
Complex fibroadenoma (approximately 3 times risk)
Moderately increased risk (4 to 5 times)
Atypical ductal hyperplasia (no family history)
Atypical lobular hyperplasia
High risk (8 to 10 times)
Ductal carcinoma in situ, low grade
Lobular carcinoma in situ
Atypical ductal hyperplasia, if history of carcinoma in primary relatives
Very high risk (precise level not known)
Ductal carcinoma in situ, high grade
Grading / Staging / Report
Grading / Staging
Lists
Biphasic lesions of the breast
Bibliography
Rosen PP, Oberman HA. Tumors of the Mammary Gland, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 7, 1993
Lerwill MF. Biphasic lesions of the breast. Semin Diagn Pathol. 2004 Feb;21(1):48-56.
Dehner LP, Hill DA, Deschryver K. Pathology of the breast in children, adolescents, and young adults. Semin Diagn Pathol. 1999 Aug;16(3):235-47.
Powell CM, Cranor ML, Rosen PP. Multinucleated stromal giant cells in mammary fibroepithelial neoplasms. A study of 11 patients. Arch Pathol Lab Med. 1994 Sep;118(9):912-6.
Musio F, Mozingo D, Otchy DP. Multiple, giant fibroadenoma. Am Surg. 1991 Jul;57(7):438-41.
Raganoonan C, Fairbairn JK, Williams S, Hughes LE. Giant breast tumours of adolescence. Aust N Z J Surg. 1987 Apr;57(4):243-7.
Dupont WD, Page DL, Parl FF, Vnencak-Jones CL, Plummer WD Jr, Rados MS, Schuyler PA. Long-term risk of breast cancer in women with fibroadenoma. N Engl J Med. 1994 Jul 7;331(1):10-5.
Silverman JS, Tamsen A. Mammary fibroadenoma and some phyllodes tumour stroma are composed of CD34+ fibroblasts and factor XIIIa+ dendrophages. Histopathology. 1996 Nov;29(5):411-9.
