A case report of primary small cell carcinoma of the breast and review of the literature
In October 2011, a 39-year-old woman presented a painless mass in her left breast for 3 months. There were no accompanying symptoms such as nipple retraction, dimpling, or palpable axillary lymph nodes. Physical examination revealed a 2 cm × 2 cm, elastic, firm, ill-defined suspicious mass in the upper outer quadrant of her left breast. On the mammography, the mass appeared round with indistinct margins with lots of punctates and scattered calcifications along the duct ().\nAdditionally, an ultrasound scan revealed two solid and low heterogeneous echoes in the left breast: one was in the 3 o'clock position, 35 mm away from the nipple (); the other was also in the 3 o'clock position, 65 mm away from the nipple (). Both were poorly defined with irregular borders. However, the levels of serum tumor markers, including carcino-embryonic antigen (CEA), carbohydrate antigen 125 (CA125), CA15-3, and CA19-9 were all within normal limits.\nThe patient did not undergo a fine needle biopsy. An intraoperative biopsy confirmed the pathologic diagnosis of SCC with the component of ductal carcinoma in situ (DCIS). As a result, she underwent modified radical mastectomy with axillary lymph node dissection. Microscopically, the mass (in the 3 o'clock position, 35 mm away from the nipple) was about 0.8 cm × 0.5 cm × 0.5 cm, which was diagnosed histologically as an intermediate grade DCIS, whereas the second mass (in the 3 o'clock position, 65 mm away from the nipple) was about 1.4 cm × 1.2 cm × 0.6 cm and was comprised of intermediate grade DCIS (30%) and SCC (70%). Histological examination showed that the tumor was composed of small round or oval cells with a high nucleocytoplasmic ratio, small hyperchromatic nuclei, inconspicuous nucleoli, and scant cytoplasm, which were arranged diffusely and patchily. Widespread necrosis was present (). Immunohistochemically, tumor cells of the DCIS component were positive for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). However, the tumor cells of the SCC component were negative for these markers, whereas the Ki67 proliferation index (percentage of Ki67-positive cancer nuclei) was 70%. Furthermore, the SCC tumor cells were highly positive for neuroendocrine differentiation markers including synaptophysin (), neuron specific enolase (NSE) (), thyroid transcription factor-1 (TTF1) (), and CD56 (), but they were negative for chromogranin A (CgA) (). Histological examination also demonstrated 1 positive lymph node out of 13 level I axillary lymph nodes.\nTherefore, a search for a non-mammary primary site was carried out, especially focusing on pathologic changes in the lungs. The result of computed tomography (CT) scans of the neck, chest, and upper abdomen were all within normal limits, and bone scintigraphy was negative for metastatic disease. As a result, we concluded that the breast was the primary site, and primary SCC of the breast was diagnosed.\nThe patient was treated with six cycles of docetaxel (75 mg/m2) and carboplatin (350 mg/m2) in combination once every three weeks. After the initial treatment, the patient was clinically monitored for disease relapse and metastasis.