When limited material, in the form of needle aspirates, core biopsy specimens or frozen sections, is submitted for histology, making a diagnosis of LGAC is not only challenging, but may be impossible. In difficult cases, careful pathological assessment, clinicopathological correlation and follow-up or complete excision biopsy may prove invaluable in establishing a definitive diagnosis.

Aims: To assess inter/intraobserver variability in the interpretation of a series of digitised images of columnar cell lesions (CCLs) of the breast. Methods: After a tutorial on breast CCL, 39 images were presented to seven staff pathologists, who were instructed to categorise the lesions as follows: 0, no columnar cell change (CCC) or ductal carcinoma in situ (DCIS); 1, CCC; 2, columnar cell hyperplasia; 3, CCC with architectural atypia; 4, CCC with cytological atypia; 5, DCIS. Concordance with the tutor's diagnosis and degree of agreement among pathologists for each image were determined. The same set of images was re-presented to the pathologists one week later, their diagnoses collated, and inter/intraobservor reproducibility and level of agreement for individual images analysed. Results: Diagnostic reproducibility with the tutor ranged from moderate to substantial (k values, 0.439-0.697) in the first exercise. At repeat evaluation, intraobserver agreement was fair to perfect (k values, 0.271-0.832), whereas concordance with the tutor varied from fair to substantial (k values, 0.334-0.669). There was unanimous agreement on more images during the second exercise, mainly because of agreement on the diagnosis of DCIS. The lowest agreement was seen for CCC with cytological atypia. Conclusions: Interobserver and intraobserver agreement is good for DCIS, but more effort is needed to improve diagnostic consistency in the category of CCC with cytological atypia. Continued awareness and study of these lesions are necessary to enhance recognition and understanding.

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