Incidence of and risk factors for sentinel lymph node metastasis in patients with a postoperative diagnosis of ductal carcinoma in situ

BackgroundPositive sentinel lymph nodes (SLNs) are found in up to 13 per cent of women with a preoperative diagnosis of ductal carcinoma in situ (DCIS) of the breast and in up to 4 per cent of those with a postoperative diagnosis. This retrospective national register study investigated the incidence of positive SLNs in women with a postoperative diagnosis of DCIS, and the value of additional tumour sectioning to identify occult tumour invasion. MethodsAll surgical patients with a final histopathological diagnosis of pure DCIS registered in the Swedish national breast cancer register in 2008 and 2009 were eligible. Additional sectioning was performed on archived primary tumour tissue from women with SLN metastasis (including cases of isolated tumour cells) and matched SLN-negative control patients with the aim of detecting occult invasion. ResultsSLN tumour deposits were reported in 11 of 753 women who had SLN biopsy (macrometastases, 2; micrometastases, 3; isolated tumour cells, 6), resulting in a SLN positivity rate of 07 per cent (5 of 753). Occult invasion was found in one (9 per cent) of these 11 patients and in two (10 per cent) of 21 control patients. No risk factors for SLN metastasis were identified. ConclusionSLN positivity is rare in women with a histopathological diagnosis of pure DCIS. Additional primary tumour assessment may reveal occult invasion in both SLN metastasis-positive and -negative patients. The value of performing SLN biopsy in the setting of a preoperative diagnosis of DCIS was limited, and current Swedish practice should therefore be questioned. No support for routine SLNB in DCIS