Clinical history: 68 year old female with irregular hypoechoic 1.5 cm mass at 11:00 in the left breast. Ultrasound guided core needle biopsies.
What is the diagnosis?
Metaplastic carcinoma with spindle cell differentiation
CKPAN - Positive
CK5 - Positive
P40 - Positive
Vimentin - Positive
SMA - Positive
Desmin - Negative
B-catenin - Positive within the cytoplasm.Negative for nuclear staining.
CD34 - Negative
S100 - Negative
The purpose of this case is to discuss the differential diagnosis of a spindle cell lesion in the breast.
The differential diagnosis for lesions composed of bland spindle cells includes: scar, fibromatosis, myofibroblastoma, pseudoangiomatous stromal hyperplasia (PASH), adenomyoepithelioma and metaplastic carcinoma.
If the lesion is composed of atypical spindle cells the differential diagnosis includes: metaplastic carcinoma, malignant phyllodes tumor, nodular fasciitis, primary sarcoma, metastatic sarcoma, metastatic sarcomatoid carcinoma and metastatic malignant melanoma.
When evaluating a spindle cell lesion in the breast, a spindle cell (metaplastic carcinoma) is much more likely than a sarcoma and must always be excluded by morphologic and immunohistochemical methods.
In this case there were no conventional areas of epithelial carcinoma however, by immunohistochemistry, the tumour cells were positive for CKPAN, CK5 and p40 confirming an epithelial origin.