Case of the month - August 2007 - discussion

• The thumbnail images alongside remind you of the main features in this biopsy - click on each thumbnail to return to the original images.





• The following features are seen:



• A dominant malignant spindle cell component



• Scattered nests of malignant epithelial cells showing glandular and squamoid differentiation



• Both epithelial and some of the spindle cell elements stain with epithelial markers



• The tumour is strongly CK5/6 positive indicating a basal cell phenotype - see reference



• The co-expression of CK7 & CK5/6 in this case is worthy of comment. These tumours commonly show 'basal' characteristics and the distinction between 'luminal' and 'basal' types is not always as clear-cut as we would like



• The tumour was also shown to be ER negative - a frequent finding in these cancers

• As a practice point if you are ever presented with a biopsy showing either a wholly or predominantly spindle cell lesion in the breast you should do two things:



• Look hard for an epithelial component including taking extra blocks from an excision



• Use immunohistochemistry to see whether the spindle cell element expresses (even patchily) epithelial markers - CK5/6 is the most reliable in our hands







• The WHO classification defines this tumour as follows:



• A heterogeneous group of neoplasms generally characterised by an intimate admixture of adenocarcinoma with dominant areas of spindle cell, squamous, and/or mesenchymal differentiation....... and that the metaplastic spindle cell and squamous cell carcinomas may present in a pure form without any recognizable adenocarcinoma



• The following subclassification is recommended by the WHO:



• Epithelial tumours with spindle cell differentiation including:



• Squamous cell carcinoma


• Adenocarcinoma with spindle cell differentiation


• Adenosquamous carcinoma (including mucoepidermoid carcinoma)


• Mixed epithelial/mesenchymal tumours:



• Mixed epithelial and mesenchymal tumours e.g. showing chondroid or osseous differentiation


• Carcinosarcoma

Prognosis

• Axillary node metastases are relatively rare in metaplastic carcinomas - 10-30% of cases



• It is difficult to generalise about overall survival because different series tend to report different case mixes



• An overall 5 year survival of about 60% is a reasonable estimate



• After adjustment for tumour size and node status, metaplastic carcinomas probably have a better survival than their ductal counterparts

See also Case of the Month September 2006 for consideration of other basal phenotype carcinomas

Reference:

• Reis-Filho JS, Milanezi F, Steele D et al
  Metaplastic breast carcinomas are basal-like tumours. Histopathology 2006;49:10-21.

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