Axillary sentinel node imprint cytology: Comparison of sensitivity of detection of macrometastases from lobular and ductal carcinomas

Background: Imprint cytology (IC) is a useful method of detecting metastatic breast carcinoma in sentinel lymph nodes (SLN). Identifying invasive lobular carcinoma (ILC) may be difficult and depends on critical attention to node examination, imprint technique and cytological evaluation.Aims: Determine sensitivity of detection of sentinel lymph node macrometastases in breast carcinomas by imprint cytology and compare results with other centres.Methods: All reports from cases of ILC with IC of SLN during 2010-2014 were reviewed. A comparable size series of invasive ductal carcinomas (IDC) was created using 20 cases/year over the same period. Imprint slides with discordance between intraoperative assessment and histopathology reports were reviewed.Results: There were 90 cases of ILC. 13 of 19 macrometastases were diagnosed by IC (sensitivity 68%). Of 6 false negative cases, 2 were ‘positive’ on review. There were 102 cases of IDC. 10 of 12 macrometastases were diagnosed by IC (sensitivity 83%). Neither of the 2 false negative cases by IC was ‘positive’ on review. No false positive diagnoses of malignancy were recorded. None of the cases with micrometastases or isolated tumour cells were positive by IC for ILC (5, 4 respectively) or IDC (4, 5). Review of histological material suggested suboptimal macroscopic assessment and slice thickness for some nodes.Conclusions: The audit demonstrated 100% predictive value of imprint cytology diagnosis of macrometastases in ILC and IDC. The sensitivity of detection was marginally less for ILC than IDC (p=0.4325), but was in accord with international figures. There is potential for improvement in macroscopic assessment, imprint technique and in utilisation of second opinion or frozen section in difficult cases. Background: Imprint cytology (IC) is a useful method of detecting metastatic breast carcinoma in sentinel lymph nodes (SLN). Identifying invasive lobular carcinoma (ILC) may be difficult and depends on critical attention to node examination, imprint technique and cytological evaluation. Aims: Determine sensitivity of detection of sentinel lymph node macrometastases in breast carcinomas by imprint cytology and compare results with other centres. Methods: All reports from cases of ILC with IC of SLN during 2010-2014 were reviewed. A comparable size series of invasive ductal carcinomas (IDC) was created using 20 cases/year over the same period. Imprint slides with discordance between intraoperative assessment and histopathology reports were reviewed. Results: There were 90 cases of ILC. 13 of 19 macrometastases were diagnosed by IC (sensitivity 68%). Of 6 false negative cases, 2 were ‘positive’ on review. There were 102 cases of IDC. 10 of 12 macrometastases were diagnosed by IC (sensitivity 83%). Neither of the 2 false negative cases by IC was ‘positive’ on review. No false positive diagnoses of malignancy were recorded. None of the cases with micrometastases or isolated tumour cells were positive by IC for ILC (5, 4 respectively) or IDC (4, 5). Review of histological material suggested suboptimal macroscopic assessment and slice thickness for some nodes. Conclusions: The audit demonstrated 100% predictive value of imprint cytology diagnosis of macrometastases in ILC and IDC. The sensitivity of detection was marginally less for ILC than IDC (p=0.4325), but was in accord with international figures. There is potential for improvement in macroscopic assessment, imprint technique and in utilisation of second opinion or frozen section in difficult cases.