Phyllodes Tumours
Clinical basics
- Uncommon, generally well circumscribed lumps belonging to the fibroadenoma 'family'
- Account for 2.5% of all fibroepithelial lesions of the breast
- Patient usually older than 40 years
- In Asian countries occur at an earlier age (average 25-30 yrs)
- Lesion usually larger than 4 cm
- May be a history of recent growth
- Principal clinical concern is the risk of local recurrence after excision, also....
- ....very rarely, malignant transformation with metastatic potential
- Malignant lesions more common in Latino whites, particularly those born in Central & South America
Classification and behaviour of Phyllodes Tumours (PTs)
Classification
- Benign
- Borderline or low grade malignant
- Malignant
Behaviour
| |
Benign
| Borderline
| Malignant
|
| Local Recurrence (%)
| 15 |
25 |
30 |
| Distant Metastases (%)
| 0 |
5 |
20 |
Note:
- First recurrences of benign PTs invariably benign
- Benign PTs tend to recur later than borderline PTs
- Borderline PTs tend to recur later than malignant PTs
- Recurrences of borderline & malignant PTs often show grade deterioration
Pathological problems
Excisions:
- Separating cellular fibroadenomas from benign PTs
- Separating benign PTs from borderline PTs
- Separating borderline PTs from malignant PTs
Cores:
- All of the above but even harder - see proposed approach below...
- Sampling - the lesion can be quite heterogeneous in an excision and the core may miss the 'bad' bit
Excisions and cores:
- Taking into account allowable variation for a patient's age - particularly younger patients (< 35 years old)
- Sampling
Pre-operative diagnosis of PTs
Main points to be considered:
- Stromal/epithelial balance
- Stromal cellularity, atypia & mitotic activity
- Margins - pushing or infiltrating - cannot usually be assessed on a core
The following three illustrations from a core biopsy of a FIBROADENOMA sets the scene for discussion about
assessing core biopsies in suspected PTs
Core biopsy of a fibroadenoma showing even distribution of epithelial and stromal components and low/moderate stromal cellularity
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The green line shows the demarcation between specialised stroma (red arrows) around glands (note orientation of stromal fibroblasts) and the non-specialised stroma (A)
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The following sequence of four images are from a core from a 5cm mass in a young woman (< 30 yrs) with a history
of a previous lesion at the site.
The biopsies were reported as supicious of phyllodes tumour for discussion at a
multidisciplinary meeting (MDM) to guide further management.
At the MDM it was decided to excise the lump with a narrow margin of normal breast tissue
- the alternatives were to "shell out" or carry out a formal wide excision.
The red arrows indicate areas of hypercellular stroma while the blue arrow shows less cellular stroma. Note also the relatively poor representation of specialised
stroma in these biopsies
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The left hand image shows a focus of increased stromal cellularity (top left of picture).
The right hand image shows a solitary stromal mitosis (black arrow) within specialised stroma adjacent to glandular epithelium (red arrow).
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Low power view of another area of this biopsy showing variable stromal cellularity: (A) hypercellular; (B) normocellular.
The distinction between specialised and non-specialised stroma is partly lost.
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Core biopsy of a subsequently confirmed PT:
The central area of this core shows the leaf like 'intra-canalicular' pattern typical of PTs. Note also the variability of stromal
cellularity in different areas of this biopsy and in particular the hypercellularity of the stroma in the central section.
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The left hand image shows a focus of increased stromal cellularity.
The right hand image shows three stromal mitoses (arrows) within specialised stroma adjacent to glandular epithelium - also see insert.
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Diagnosis on excisions
- Be suspicious about a 'fibroadenoma' if it is large (> 35mm) and from an older woman (> 35 yrs)
- The surgeon may alert you to a history of recent growth
- Serially section the specimen and look carefully for more abnormal areas
- Block generously and consider putting the whole specimen through if practicable ...
- ... the WHO Guide (ref) recommends one block for every cm of maximum lesion dimension
The following table gives pointers to help distinguish histologically the various 'grades' of PT. It is emphasised that these criteria should NOT be taken as absolute but as a guide.
It should be noted also that there are considerable variations in the literature as to what constitutes a 'cut off' point for a particular criterion.
| |
Benign
| Borderline
| Malignant
|
| Pushing boundary
| Yes |
Usually |
Not usually |
| Stromal/epithelial balance
| Even |
Even |
Uneven |
| Stromal cellularity
| High |
High |
High |
| Variability of stromal cellularity
| Yes |
Yes |
Yes ++ |
| Stromal mitoses /10 hpf
| < 5 |
5 - 10 |
>10 |
Benign PTs
The following sequence of images are from a benign PT:
Low power view of a PT. At this power all that can be stated is that it is a fibroadenomatoid lesion with an intracanalicular pattern.
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The left hand image demonstrates well the leaf-like contours of the exaggerated intracanalicular growth pattern.
The right hand image shows increased (and variable) stromal cellularity.
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High power view of benign phyllodes tumour showing a stromal mitosis.
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The following sequence of images are from a borderline PT:
Macro view of a borderline PT. The cut surface shows exaggerated lobulation.
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The left hand image demonstrates well the leaf-like contours of the exaggerated intracanalicular growth pattern.
The right hand image shows increased (and variable) stromal cellularity.
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Medium power view of a borderline PT with involvement of an excision margin.
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Malignant PTs
Macro of a malignant PT (wide local excision specimen) - black arrow indicates poorly demarcated but pushing edge of lesion; red arrow indicates degenerate central area
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This low power image demonstrates well the loss of stromal - epithelial balance in a malignant PT.
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The left hand image demonstrates well the infiltrating interface of the tumour with surrounding fatty breast tissue.
The right hand image shows stromal overgrowth.
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Selected views of phyllodes tumour with hpercellular stroma and infiltration of fat
Click on images for further detail
Malignant Phyllodes Tumour:
The left hand image shows a focus of stromal osseous metaplasia.
It should be noted that heterologous stromal metaplasia such as this
may occur in any of the 'grades' of PT but is more common in borderline and malignant lesions.
The right hand image shows a leaf-like structure with increased stromal cellularity and mitoses (arrows).
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