Case of the month - August 2006 - discussion

Sections show an invasive carcinoma with striking cytoplasmic foamy change, PAS-positive & partly diastase-resistant cytoplasmic granules, large central nuclei with some prominent nucleoli. ER and S100 are negative. Note the in situ component.

At this stage the working diagnosis is apocrine carcinoma. Histologically it is a good fit particularly the PAS reactions and the negative ER. At this time lipid-rich carcinoma cannot be excluded because the Oil Red-O stain has to be done on frozen sections and will be carried out on the excision.

There is a need for caution about diagnosing specific types of carcinoma on core biopsy because there is a requirement for 90% of the tumour to show the relevant histological features (see also Special types of breast carcinoma). Clearly, core biopsies are prone to sampling errors and some caveat should be given in the report such as 'features of....' or similar.

Note that I have called this a 'specific type' of carcinoma and not a 'special type'. 'Special Types' of carcinoma often carry an implication of a better prognosis whereas tumours such as apocrine carcinoma while requiring the same degree of rigorous diagnosis are regarded as variant forms of NST carcinoma and are included in the subgroup 'other invasive carcinomas'.

Differential diagnosis:

This is given in the table below but should also include:

• Atypical apocrine sclerosing lesions - use a CK 5/6 stain or similar to distinguish - see also pseudo-infiltrative lesions



• Granular cell tumour



• Histiocytic disorders

Prognosis of apocrine carcinomas:

• similar stage-for-stage to ductal carcinomas NST

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