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Fibroadenoma

Fibroadenomas (Fig. 8.8) are mixed fibroepithelialtumors. Depending on the endotumoral distribution ofthe stromal and epithelial components, they areclassified as intracanalicular and pericanalicular fi-broadenomas. This differentiation is of no clinical im-portance. In younger women, fibroadenomas typicallyhave a high proportion of epithelial tissue.With increas-ing age, and especially in postmenopausal women, thefibrotic component of these tumors predominates andmay exhibit progressive hyalinization and calcification(Figs. 8.14−15, and 8.18).

General information

Incidence: Most common benign breast tumor (�10% of all women).Age peak: All ages, peak between 20 and 50 years.Risk of malignanttransformation: Very low (factor 1.3−1.9).Multifocality: 10−15%.

Findings

Clinical: Well-circumscribed, movable, painless mass.Mammography: Well-circumscribed, homogeneously dense lesion (round, oval, or lobulated),

possible halo sign.Endotumoral popcorn macrocalcifications (�2mm).Cave: Endotumoral or peritumoral pleomorphic microcalcifications (differentialdiagnosis: carcinoma).

Ultrasonography: Well-circumscribed, oval lesion with homogeneous internal echo texture.Moderate to strong posterior acoustic enhancement, possible bilateral acousticshadowing.Macrocalcifications may cause complete posterior acoustic extinction.Compressibility of lesion: slight to good, depending on histologicalcomposition.

Clinical significance

Fibroadenomas must be differentiated from well-defined malignant tumors, especially in older women. Ifthere is uncertainty about the histology, further diagnostic procedures are indicated to rule out malignancy(e.g., percutaneous biopsy).

8 Benign Changes

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Fig. 8.8 Fibroadenoma.Ultrasound shows well-circumscribed, oval lesion with homo-geneous internal echo texture and narrow bilateral posteriorshadowing.

Fig. 8.9 Fibroadenoma within parenchyma.Difficult detection of fibroadenoma due to only slightly lowersignal intensity of lesion (arrows) compared to surroundingparenchyma in T1-weighted precontrast image.

Fig. 8.10 Fibroadenoma within fatty tissue.Clear demarcation of oval fibroadenoma within surroundingsignal-intense fatty tissue in T1-weighted precontrast image.

MR mammography: Fibroadenoma

T1-weighted sequence (precontrast)Well-circumscribed round, oval, or lobulated le-sion. Isointense or slightly hypointense signal incomparison to breast parenchyma. If locatedwithin parenchymal body, therefore, it is difficultor impossible to detect (Fig. 8.9). If located withinfatty tissue, lesion appears more obvious(Fig. 8.10). In rare cases, endotumoral signal lossdue to macrocalcifications (Fig. 5.1c).

Fibroadenoma

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MR mammography: Fibroadenoma

T2-weighted sequenceSignal behavior is dependent upon the histologi-cal composition of the fibroadenoma:When a high proportion of epithelial tissue is pre-sent (more often in younger women), signal inten-sity is often high, making the differentiation froma cyst difficult (Fig. 8.11). Occasionally endo-

tumoral septations, correlating to fibrotic tumorcomponents, are seen (Note: The selection of awide window is important!).When a high proportion of the tumor is fibrotic(more often seen in older women), the fibroade-noma is usually not detectable because of theisointensity or slight hypointensity of the signal incomparison to the surrounding parenchyma(Fig. 8.12).

Fig. 8.11a, b Fibroadenoma with high epithelial com-ponent.a Subtraction image demonstrating hypervascularized lesion.

b T2-weighted image showing high signal intensity of lesion.Histology: Myxoid fibroadenoma.

Fig. 8.12a, b Fibroadenoma with high fibrotic component.a Subtraction image demonstrating hypovascularized lesion

(arrows).

b T2-weighted image showing predominantly hypointense le-sion.Unchanged over several years in ultrasonography.

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Fig. 8.13a, b Hypovascularized fibroadenoma.a Oval lesion within fatty tissue in the upper outer quadrant of

the right breast. Very slow CM uptake within the lesionduring dynamic examination. Dynamic images before and 1,3, and 5 minutes after CM administration.

b The signal curve analysis shows slight initial contrast en-hancement (�50%) and continuous postinitial signal in-crease (in several ROIs).

Histology: Fibroadenoma.

a

b

MR mammography: Fibroadenoma

T1-weighted sequence (contrast-nhanced)The signal behavior of a fibroadenoma after con-trast administration is dependent upon the histo-logical composition of the tumor:

Tumors with a high proportion of epithelial tissue(more frequent in younger women) show pro-nounced contrast enhancement. The strong initialcontrast enhancement (up to several hundredpercent of precontrast value) occasionally reachesvalues higher than those found inmanymalignanttumors. The postinitial signal usually displays acontinuous increase or plateau. A wash-out phe-nomenon is extremely rare (�1% in our collec-tive). Endotumoral septations with slight CM up-take represent linearly distributed fibrotic tumorportions (see Fig. 8.17). In rare cases, a nonen-hancing peripheral border is seen as the expres-sion of a pseudocapsular demarcation (MR equiv-alent of halo sign) (see Fig. 8.16).

Tumors with high proportion of fibrotic tissue(more often in older women) (Fig. 8.13) showno or slight CM uptake. There is correspondinglyno or slight contrast enhancement after contrastadministration with no or continuous postinitialsignal increase during the examination. Differen-tiation from carcinoma is usually unproblematic.

Fibroadenoma

Fischer. Practical MR Mammography (ISBN 3131320311) © 2003 Georg Thieme Verlag