Metaplastic breast carcinoma
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Metaplastic breast carcinoma, also known as spindle cell carcinoma of the breast, is a rare form of primary breast malignancy and accounts for <5% of breast carcinomas ref.
These are scarce lesions, rarely seen in general radiology practice. The lesions usually present as a mass in postmenopausal women. Mammography shows a mass that is dense and has both smooth, well-defined margins and spiculated edges. Ultrasound images show mixed echogenicity lesions taller than wide.
Patients are commonly postmenopausal and older than 50 years, with an average age at diagnosis of ~55 years.
These lesions present as a palpable mass that is often rapidly growing 1,3. Axillary node involvement at the time of diagnosis is uncommon.
These lesions are considered ductal carcinomas that undergo metaplasia to a glandular growth pattern. There are five variants:
matrix producing carcinoma of the breast
squamous cell carcinoma of the breast
spindle cell carcinoma of the breast
carcinosarcoma of the breast (the rarest primary breast malignancy)
metaplastic carcinoma of the breast with osteoclastic giant cells
These lesions have pathological features of both carcinoma and sarcoma. There is a mixture of glandular epithelial elements and mesenchymal malignant elements. The spindle cell component in 98% of spindle cell carcinomas is immunoreactive for keratin ref.
Phyllodes tumors and sarcomas are usually negative for p63 expression. In metaplastic carcinoma, the sensitivity for p63 is 86.7% and the sensitivity is 99.4% ref.
On mammography, these are usually large masses, with a mean diameter at the time of diagnosis of 4.2 cm ref. The masses are rounded densities with margins that are smooth, well-defined and spiculated. Calcification is very rare.
On ultrasound the masses are round to ovoid, sometimes microlobulated, with solid and cystic components related to hemorrhage or necrosis. Most masses have well-defined margins 3.
T2: often displays very high signal 2
Treatment and prognosis
Local recurrence is generally not ominous and is fatal in ~30% of cases ref.
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