Table 1

Comparison of OSNA and histology for the nodal staging of breast cancer

GeneralComplex but subjective evaluation that gives more information than nodal staging, can detect other nodal lesions (lymphoma, leukaemic infiltration, capsular nevi, epithelial inclusions, specific lymphadenitis types such as toxoplasmosis and tuberculosis in the authors experience)Indirectly detects CK19, and can only be used for staging
MorphologyThis is of prime importance in identifying a metastasis and distinguishing it from other possible mimicsNone, unless tissue is divided for OSNA and microscopy
QuantificationGenerally based on the largest dimension of two-dimensional evaluation, sometimes complemented by estimations based on the third dimension (step sectioning)Quantification of CK19 mRNA RT–LAMP reaction by-product reflecting tumour burden (volume)
StagingStaging categories such as minimal nodal involvement belonging to the ITC category, micrometastasis and (macro)metastasis are defined on the basis of microscopic size and cell numbers,15 16 but are less than optimally reproducibleNot suitable for measurements, but a semiquantitative display of metastatic volume-related results more or less matching the arbitrary categories of micrometastasis and (macro)metastasis.
SamplingVariable, depending on the distance between cut surfaces produced for microscopy; the interval tissue is discardedThe tissue used for OSNA is completely investigated
ProtocolVariable from department to department17Standardised
Time requirementA day or more for permanent sections, but only 10–20 min for imprint cytology, and a frozen section; could be similar to OSNA when combined with rapid immunohistochemistry7 or when doing a labour-intensive frozen sectioning protocol5Minimum and maximum reported are 2218 and 11619 min, respectively. Mean or median times reported are between 32 and 62 min, depending on the number of samples
  • CK19, cytokeratin 19; ITC, isolated tumour cells; OSNA, one-step nucleic acid amplification; RT–LAMP, reverse transcription loop-mediated isothermic amplification.