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Original Article |
Department of Surgery, Atlanta Medical Center, Atlanta, GA, USA
Correspondence: Address correspondence and reprint requests to: George Michael Fuhrman, MD; E-mail: george.fuhrman{at}tenethealth.com
The role of sentinel node mapping and biopsy in the management of ductal carcinoma in situ (DCIS) remains controversial. A debate about the use of a staging technique for the evaluation of a malignancy without metastatic potential seems absurd. However, this debate is fueled by two factors. First, some patients diagnosed with DCIS will ultimately prove to have invasive carcinoma. Second, the status of the sentinel node is the most powerful predictor of prognosis and surgeons want to ensure that those patients with invasive carcinoma have sentinel node mapping for staging and treatment planning. In order to understand this debate an appreciation of the evolution of breast cancer management over the past decade is essential. The two most important historical events in this evolution have been the appreciation of the relationship of prior lumpectomy and its impact on lymphatic drainage from the breast to the sentinel node, and the increasing use of image guided core needle breast biopsies to sample mammographic abnormalities that may underestimate the extent of breast pathology.
When Morton et al.1 initially described the use of sentinel node mapping for melanoma, a minimally or undisturbed primary tumor site was considered essential for accurate identification of the sentinel node. In fact, a wide excision of a primary melanoma prior to referral for sentinel node mapping was considered a contraindication and these patients were denied sentinel node staging. When sentinel node mapping was initially described for breast carcinoma, a precise injection of colloid and/or dye around an intact primary tumor were considered important technical aspects in order to identify the correct sentinel node in the axilla.2 Like melanoma patients, if the primary breast tumor was removed prior to referral for sentinel node mapping, the potential inaccuracy of the technique was used as a criterion to exclude patients from mapping. Mapping was done routinely at the time of DCIS management to avoid losing the opportunity to stage the axilla after excision when invasive carcinoma was subsequently identified. Subsequent experience in melanoma and breast sentinel node mapping has demonstrated that the technique is still accurate after wide excision of the primary tumor.3,4 The evidence that mapping techniques that call for injection away from the primary tumor site (subareaolar) provide additional support for sentinel node mapping after prior breast excision.5 Despite the evidence that wide excision does not impact mapping, the concern about losing the opportunity to identify the sentinel node is still valid today for DCIS patients that either choose or require mastectomy as their treatment. Mapping must be done at the time of mastectomy to avoid the dilemma of losing the opportunity of identifying the sentinel node for patients with invasive carcinoma that is ultimately discovered in their mastectomy specimens. Since only a small volume of breast tissue is evaluated during a standard histopathologic assessment of a mastectomy specimen, a positive sentinel node biopsy can act as a surrogate for invasion that was not identified by the pathologist during the initial evaluation of the breast. Sentinel node mapping for DCIS patients treated with mastectomy ensures that axillary staging information will be available when invasive carcinoma is subsequently detected in their mastectomy specimens.
The second historical event that impacted the debate regarding when to use sentinel node mapping for DCIS was the development of image guided core needle breast biopsy techniques. While these techniques have helped patients with benign breast pathology to avoid unnecessary surgery, they have created a challenge for pathologists who must determine the extent of malignant breast pathology based on several small core samples instead of evaluating a larger excisional breast biopsy specimen. It has been well established that DCIS diagnosed by image guided core breast biopsy will often be upgraded to invasive carcinoma after complete excision.6 Interestingly, as image guided biopsy techniques were becoming more common place, the concern about alteration of lymphatic drainage led to a more routine use of sentinel node mapping for patients diagnosed with DCIS by core biopsy. While this justification is no longer valid as outlined in the preceding paragraph, an attempt to identify the subgroup of patients likely to be upgraded to invasive carcinoma has the advantage of avoiding the need for a second operation. For surgeons that care for patients that travel long and inconvenient distances for care, the limited morbidity associated with sentinel node biopsy is less disruptive than the need to return for a second operation. Routine sentinel node mapping for DCIS diagnosed by core biopsy is wasteful and unnecessary. The identification of DCIS patients at high risk for having invasive cancer that can be evaluated by sentinel node mapping at the time of lumpectomy, can limit the need for second operations.
Attempts to define high risk criteria that would predict invasive carcinoma are important for treatment planning and include palpable DCIS, radiographic involvement of greater than 4 cm, high nuclear grade, and questionable areas of microinvasion.7,8 It is important to separate patients with clear evidence of microinvasion on core biopsy from this debate. Patients with microinvasion are at risk for having nodal metastasis and should be evaluated with sentinel node mapping.
In summary, there is a role for sentinel node mapping in patients with DCIS. Sentinel node mapping should always be included as part of a mastectomy for DCIS to avoid the dilemma of how to stage patients with subsequently discovered invasive carcinoma in the mastectomy specimen. Additionally, sentinel node mapping should be considered for patients thought to be at high risk for having invasive carcinoma in association with DCIS diagnosed by core needle biopsy. This is especially important for patients looking to avoid second procedures. Sentinel node biopsy is not indicated for patients diagnosed with "pure" DCIS by excisional biopsy or DCIS diagnosed by core biopsy without features that might suggest coexistent invasive carcinoma. While DCIS remains a disease without metastatic potential, its association and coexistence with invasive carcinoma requires a selective approach to staging to ensure that all patients subsequently diagnosed with invasive carcinoma can benefit from the prognostic information provided by sentinel node mapping.
Received for publication October 5, 2006. Accepted for publication November 20, 2006.
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