Case of the month - December 2006 - discussion

Diagnosis - Phyllodes tumour - borderline /low grade malignant type

This patient had a phyllodes tumour, borderline type, excised 3 years previously. The case was discussed at a multidisciplinary meeting at that time and re-excision of the biopsy site was recommended. This was carried out 6 weeks after the first operation and no residual tumour was identified. The recurrence was at the same site as the original lesion and the core biopsy was reported as showing features of recurrent phylodes tumour. The excised recurrence looks very similar to the original lesion.

The following features are present in the recurrence:

• Biphasic lesion showing preservation of stromal-epithelial balance



• Epithelial proliferation without atypia



• Pushing margin



• Stromal hypercellularity with stromal atypia and frequent mitotic figures - some severely atypical


• Stromal giant cells - the immuno suggests that these might be rhabdomyoblastic but there was a lot of background cytoplasmic epithelial staining in some areas and also, after extensive searching, I could not find any cells with cytoplasmic cross-striations

Prognosis:

• This is a difficult lesion to classify - is it still borderline or is it malignant?



• You will find differences of opinion on this subject from different authorities



• In the UK we would normally expect to see a 'full house' of diagnostic features before labelling a lesion as a malignant phyllodes tumour:-



• Stromal overgrowth


• Brisk stromal mitotic activity - >10 mitoses per 10 hpf


• An infiltrative margin




• Some authorities regard the presence of heterologous elements as strongly supportive of a malignant diagnosis



• In the end we decided that the giant cells were NOT rhabdomyoblasts - therefore NOT heterologous



• Phyllodes tumours tend to undergo grade deterioration with successive recurrences



• A number of studies have investigated the use of marker profiles to distinguish malignant cases but these have to be reviwed in the light of the complete clinico-pathological picture. See references below.