DCIS WITH MICROINVASION ON CORE BIOPSY. SENTINEL NODE BIOPSY?
Approximately 10% of patients having DCIS on core biopsy will be found to have microinvasion on surgical excision (DCISM). When considering sentinel node biopsy (SLNB) for DCISM one might consider that most of the data available is based on surgical excision and not core biopsy. Therefore, should one perform SLNB when core biopsy shows either suspected or definite microinvasion? Flanagan, Stempel, Brogi, Morrow, and Cody from Memorial Sloan-Kettering (MSKCC) attempt to answer this question by reviewing patients with either definite or suspected microinvasion on core biopsy at their institution.
DCISM is defined as DCIS with one or more foci of stromal invasion, none larger than 1 mm. Overall, the authors identified 369 consecutive patients with a diagnosis of DCIS with suspected or definite microinvasion. A majority of the patients as expected were diagnosed by stereotactic biopsy following an abnormal mammogram.
As one might expect, DCIS alone was found more frequently with suspected DCISM compared to definite DCISM (51% vs. 29%). Of those with suspected DCISM, 28% were upstaged to T1 disease, compared to 35% who were upstaged to T1 disease with definite DCISM. Among 81 patients with suspected DCISM who underwent SLNB, 2 were found to have pN0i+i and 1 (<1%) had pN1disease. Of the 264 patients with definite DCISM on core biopsy, 2 patients (1%) had pN0i+ disease, 7 (3%) had pN1micro disease and 16 (6%) had pN1 or greater disease.
In conclusion, only 1% of patients undergoing SLNB for core biopsies suspicious for DCISM had clinically significant sentinel node metastases (>N0i+). This is the same incidence of N1 disease reported for DCIS.The authors from MSKCC concluded that SLNB is NOT indicated for patients with core biopsy which is suspicious for DCIS with microinvasion. However, in those patients with definite DCISM on core biopsy, 6% were upgraded to N1 disease. In these cases, the authors do recommend SLNB.