In Situ Carcinoma

As a consequence of population-based screening and the increased use of surveillance mammography, ductal carcinoma in situ (DCIS) now accounts for 20% of newly diagnosed breast cancers.   Lobular carcinoma in situ (LCIS) is not even considered cancer, and is merely a ‘high risk lesion’.

Lobular Carcinoma In Situ (LCIS)

Now also referred to as LIN – lobular intraepithelial neoplasia is a risk factor for subsequent invasive carcinoma in either breast with published relative risks of 8-10 times ‘average’.  So, not exactly ‘breast cancer’.  Treatment options of LCIS is that of all high risk patients, thus complete excision, clear margins and radiation are not indicated.

  • Pleomorphic LCIS – this is the exception; as this entity has features and behavior more like DCIS (ductal carcinoma in situ), but is still not considered or treated as cancer.  Excision to clear margins is a consideration and endocrine (hormonal) therapy is more strongly advocated.
  • When to excise?  The greatest controversy surrounding LIN/LCIS is, when to surgically excise, when this diagnosis is made by core biopsy.  Multiple studies from different institutions have yielded upgrade/upstage rates (typically to DCIS) of 11-35%.  So, multiple factors go into making the decision whether or not surgical intervention is necessary.

Ductal Carcinoma In Situ (DCIS)

The incidence of ductal carcinoma in situ has been steadily increasing with the widespread use of screening mammography and now accounts for approximately 20-25% of all breast malignancies.  Unlike invasive cancers, the size of DCIS does not have any impact on staging or outcomes.  The risk implied by having this diagnosis is that of recurrence of disease.  Patients with DCIS who recur will recur with invasive cancer in about 50% of cases.  So the goal of treatment is to reduce this risk.

  • Surgical options are similar to those for invasive cancer, including mastectomy and lumpectomy with radiation.
    • Local regional recurrence rates  are similar but not zero for any surgical treatment.  Even women treated with mastectomy have a 0.8-3.3% risk of local recurrence.
    • The need for clear margins (lumpectomy) is also similar to invasive cancer patients; prior to radiation therapy.
    • There is no indication for chemotherapy in women with pure DCIS.
  • There has been growing evidence to support the fact that not all women with DCIS need to be treated in the same fashion.  There are likely subsets of the disease whereby certain treatments may offer little if any benefit.  Being able to accurately predict which subset requires which treatment is currently under investigation.