The patient went on to have transphenoidal surgery. 


Paraffin sections show fragments of a densely hypercellular tumour. This is composed of pleomorphic cells with round, oval and angulated hyperchromatic nuclei and a small amount of dense eosinophilic cytoplasm. Scattered mitotic figures are noted. Tumour cells are arranged in linear aggregates and small irregularly shaped islands in a fibrous stroms. Infiltration of pituitary acini is also noted. Strong nuclear staining for oestrogen receptor is seen in >90% of tumour cells. Patchy strong nuclear staining for progesterone receptor is also noted as well as strong diffuse membrane staining for E-cadherin.  Strong complete membrane staining for HER-2 is seen in >90% of tumour cells. The features are of metastatic undifferentiated carcinoma arising from breast. 

  • Oestrogen receptor: positive
  • Progesterone receptor: positive 
  • HER-2: positive

FINAL DIAGNOSIS: Metastatic undifferentiated carcinoma arising from breast.