Two cases of breast cancer with cartilaginous and osseous metaplasia.

Invasive breast cancer (IBC) with cartilaginous or osseous metaplasia is rare. Here we report two cases of this unusual variation. Case 1: The patient was a 33-year-old woman with a right breast tumor, 2.2 cm in size. Mammograms (MMG) presented no specific findings, but ultrasound (US) showed a cystic-like lesion. Excisional biopsy confirmed IBC with cartilaginous and osseous metaplasia. Biopsy was followed with a modified radical mastectomy. One lymph node was positive, and both estrogen receptor (ER) and progesterone receptor (PgR) were negative. Case 2: The patient was a 43-year-old woman with a left breast tumor, 4.2 cm in size. MMGs presented no findings but US showed an irregular shaped, low-echoic area, suggesting malignancy. Core needle biopsy confirmed IBC with cartilaginous metaplasia. A total adenectomy and lymph node dissection with breast reconstruction using a lattisimus dorsi muscle flap were performed. Two of 18 lymph nodes were positive for metastasis and both ER and PgR were negative. IBC with cartilaginous or osseus metaplasia seem to be divided into two types pathologically, with or without intervening spindle cells, which is related to the prognosis. Matrix producing carcinoma (MPC) has no intervening spindle cells and a better prognosis than other types, however, MPC has been reported to have the same prognosis as ordinary breast cancer after for adjusting its stage. Our two cases were MPC's and no recurrence has been detected 5 and 3 years from the initial therapy, respectively.