Fibroepithelial and Spindle
Cell Lesions of the Breast
Fouad Boulos, MD
Fibroepithelial Lesions
• Very common
• Wide histologic spectrum
• Vast majority benign
Fibroadenoma
• Hyperplasia of the lobular unit
• Most common palpable lesion in young
women
• Peak incidence in third decade
• May present as calcifications
Fibroadenoma
• Microscopically well-defined
• Stroma with low cellularity
• Intracanalicular and pericanalicular
patterns
FA and Epithelial
Proliferations
• Kuijper et al: 396 FAs
– Hyperplasia 32%
– DCIS 1.26% (5)
– LCIS 0.76% (3)
– 3 cases of CIS involved adjacent tissue
– No invasive carcinoma
FA with…
• Carcinoma: re-excise especially if
unclear about margins and FA shelled
out
• Atypical Hyperplasia: worry? Excise?
FA with…
• Carter et al: 1,834 women with FA 195068
– 0.81% had ADH or ALH
– NO increased risk
Special FAs
• Juvenile FA
– Large
– Rapid growth (hormone sensitive)
– Gynecomastoid hyperplasia
– Increased stromal cellularity
– Differential: Phyllodes vs virginal hypertrophy
Special FAs
• Complex FA
– Apocrine change
– Calcification
– Cyst formation
– Adenosis
• Tubular adenoma
• Lactational adenoma
Fibroadenomatosis
• Multiple
• Ill-defined
• Likely to “recur”
Phyllodes Tumor
• Biphasic with epithelial and stromal
proliferation
• Stroma more cellular than FA, and has
propensity for malignant degeneration
• Local recurrence common though
majority benign
Phyllodes Tumor
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0.6% of all “malignant” breast tumors
40 and above
5 cm average size
Well-circumscribed with leaf-like pattern
Phyllodes Tumor
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Epithelial cells polyclonal
Stromal cells clonal
FA: both polyclonal
Phyllodes can arise from FA
Benign PT
• Pushing margins
• Minimal cellular atypia
• Low mitotic rate (<4 per 10 hpf)
Malignant PT
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Stromal overgrowth (4X without epithelium)
Infiltrative border
Stromal cellular atypia
High mitotic rate (10 per 10 hpf)
Borderline PT
• As the name implies
• Stromal cells cytologically similar to
benign PT
• Higher tendency for local recurrence
because of infiltration and stromal
overgrowth
Malignant PT
• Malignant heterologous elements are
definitive clues to histologically
malignant PT
– Liposarcoma
– Osteosarcoma
– Fibrosarcoma
Phyllodes Tumors
• 45 cases from Memorial Sloan-Kettering
aged 10-24 years
– 34 benign
– 11 malignant
– 6/36 with f/u showed local recurrence
– 1/36 metastasized (rhabdo)
Phyllodes Tumors
• 101 patients from MD Anderson
– 58 benign, 12 borderline, and 30 malignant
– 8 with distant mets
– 13% 10-year rate
– Stromal overgrowth is the only
independent risk factor.
Phyllodes Tumors Outcome
Benign
(Compiled from 7 studies)
#
150
Rec
17%
Mets
0
Death
0
Phyllodes Tumors Outcome
Borderline
(Compiled from 7 studies)
#
36
Rec
33%
Mets
6
Death
6
Phyllodes Tumors Outcome
Malignant
(Compiled from 7 studies)
#
131
Rec
15%
Mets
8
Death
8
SEER Data (1983-2002)
• 821 malignant PT cases
– 91% survival at 5 years
– 89% survival at 15 years
– Wide excision equivalent to mastectomy
Few Pointers
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Fibroadenoma with phyllodal features
CD10
Epithelium can be very proliferative
Metaplastic carcinoma within phyllodes
Always look hard for the epithelial
component (PT much more common
than primary sarcomas in the breast)
Summary
• Wide excision very important
• The more it looks like a soft tissue
sarcoma, the more likely it is to behave
like one
• Rarely an aggressive tumor with fatal
outcome
Spindle Cell Lesions
• All spindle cell lesions occurring in the
soft tissues can happen in the breast
• Overlapping morphologies for drastically
different lesions
• Important to maintain a wide differential
Spindle Cell Lesions
• Myofibroblastoma
• Fibromatosis
• Nodular fasciitis
AND
Their differentials…
Myofibroblastoma
• Originally thought to be a neoplasm of
the male breast
• Wide age range
• Average size of 2.5 cm
• Usually well-circumscribed
Myofibroblastoma
• Wide range of morphologies
– Bland spindled to epithelioid cells with
amphophilic cytoplasm in fascicles, singly,
or in small clusters
– Well-defined or infiltrating
– Collagen or myxoid stroma
– Pleomorphism (pleomorphic lipoma-like)
Myofibroblastoma
• Immunohistochemically
– Desmin (large majority)
– CD34
– SMA
– Hormone Receptors
Pitfalls of Myofibroblastoma
• Infiltrative: Metaplastic carcinoma
• Single epithelioid cells: Invasive lobular
• Pleomorphic: Sarcoma
Pitfalls of Myofibroblastoma
• Infiltrative spindle: Metaplastic carcinoma
– CK/p63/desmin/CD34
• Single epithelioid cells: Invasive lobular
– CK/desmin
• Pleomorphic: Soft tissue sarcoma
– Overall features: no mitoses, small size,
giant cells (floret) with smudged chromatin
+/- IHC.
Fibromatosis
• As in non-mammary soft tissues,
fibromatosis is a locally aggressive
infiltrative benign mesenchymal
neoplasm
• Chest wall or primary, former more
aggressive (desmoid type)
• Frequently positive margins and local
recurrence
Fibromatosis
• 30-60 years old
• Palpable mass or suspicious
mammographic lesion
• Can cause skin changes if extends into
dermis
• Most sporadic but may occur as part of a
genetic syndrome (APC/beta catenin)
Fibromatosis
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Average size 2.5 to 3 cm
Entraps fat and epithelial structures
Variably low cellularity
Variably scant mitoses
Bland tapering nuclei and little pink
cytoplasm
• Very long fascicles
Fibromatosis
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Thick bands of collagen
Centrifugal cellularity
Thin-walled venules
Lymphoid infiltrates perivascular and
peripheral
Fibromatosis
• IHC:
– Only helpful ruling out other entities
– Nuclear beta catenin
Differential of Fibromatosis
• Scar
– The re-excision problem
• Nodular fasciitis
• Metaplastic carcinoma (fibromatosis-like)
Nodular Fasciitis
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Young adults
Small (<5 cm) and subcutaneous
Rapid preclinical phase
Can be associated with pain
Often spontaneously regresses
Often a clinical mimicker of malignancy
Nodular Fasciitis
• Histology:
– Well-defined not encapsulated
– Space occupying though can be infiltrative
– Can be quite cellular with mitoses
– Plump stellate myofibroblasts in small
whorls or fascicles and in loose matrix
– Tissue culture appearance
– No real atypia or necrosis
Nodular Fasciitis
• Histology:
– Other features:
• Thin walled vessels
• Spattering of lymphoid cells (peripheral
aggregates)
• Red cell extravasation
• Rarely osteocalst-like giant cells
– Older lesions are variably cellular, myxoid
or collagenized, with hypo/acellular center
• IHC: Actin, rarely desmin
Nodular Fasciitis
• Differential diagnosis:
– Malignant spindle cell lesions (metaplastic
carcinoma, sarcoma)
– Fibromatosis
The main and most important
differential is
METAPLASTIC CARCINOMA
A Few Words…
• In our experience, a majority of spindle
cell carcinomas are monophasic spindled
• Low-grade fibromatosis-like to high grade
pleomorphic
• Often associated with DCIS or sclerosing
lesions (low-grade)
A Few Words…
• Usually positive for 34ßE12 and p63
• Metaplastic carcinomas have a wide
variety of appearances- low threshold
for immunostaining:
– Aggressive
– Resistant to chemo
– Hematogenous spread
Take Home Messages
• Exercise extreme caution when dealing with a
core biopsy
• Benign spindle cell lesions can look malignant
and malignant ones can look benign
• When in doubt, recommend excision without
committing
• IHC very helpful but can bring you down
– Focal positivity missed
– Non-specific staining (Giant cells)
• Clinical and radiographic info should be sought