It is believed that breast cancer progresses from atypia, to ductal carcinoma in situ (DCIS), then to invasive cancer.
Lobular carcinoma in situ (LCIS) is associated with an increased risk of invasive cancer. This 15% of women with LCIS will develop an invasive carcinoma of ductal or lobular type in either breast at any site.3 In contrast to DCIS, this is not a lesion that has a natural history to become an invasive cancer. Therefore excision of this lesion does not invoke protection against developing future cancer. The only treatment for this lesion involves bilateral mastectomy or close follow up. Bilateral mastectomy has been proven to decrease future carcinoma development.
Ductal carcinoma in situ (DCIS) is a precursor to invasive ductal carcinoma. This should be treated as a malignancy. An important distinction is made between DCIS and invasive cancer in that DCIS has an intact basement membrane. Treatment involves local control as either mastectomy or lumpectomy with or without radiation depending on lesion size and type.4 A worse prognosis is associated with
lesions > 2 cm, comedo type or excisional margin that is close to the lesion (< 1 mm). These are managed with postoperative radiation for local control. The disease can be multifocal in as many as 20% and in that case mastectomy is recommended. Axillary dissection is not routinely preformed for DCIS as it is not an invasive carcinoma and should not have metastatic spread. If the DCIS lesion is 5 cm or greater in size, invasion is assumed and the lesion is treated as so.
Infiltrating ductal carcinoma is the most common breast cancer. This is observed as a stellate lesion or architectural distortion on mammogram. In contrast, invasive lobular carcinoma is often not seen on mammogram and can lead to a delay in diagnosis. Any palpable lesion should be fully evaluated.
Paget's disease resembles a rash at the nipple that indicates underlying DCIS. If there is a palpable lesion at the nipple invasion is often present.
Inflammatory breast cancer presents as an inflamed, hard breast with diagnosis made after not responding to antibiotics. A biopsy will show invasion of dermal lymphatics. Plugging of these lymphatics cause the characteristic edema and peau d'orange seen in inflammatory cancer. This patient usually presents with metastatic disease and is labeled as a T3b lesion. Treatment of inflammatory cancer involves preoperative chemotherapy, for this has been shown to provide the best survival. If the patient survives chemotherapy, mastectomy follows and the radiation to the chest wall and sometimes axilla if gross disease is present.
Cystosarcoma phyllodes is the most common type of sarcoma of the breast. Sarcomas make up < 1% of all breast cancers. This is distinguished from a benign phyllodes tumor by the amount of cellular atypia present, mitotic activity (>10/ HPF), and malignant infiltrating margins. No axillary dissection is performed because this is a sarcoma of mesoderm origin and spread by vascular routes not lymph.5 The metastatic spread here is to the lungs and follow-up CT is usually preformed. These may recur at the primary site and require reexcision. There has been no proven advantage with chemotherapy or radiation pre- or postoperatively.
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