Introduction Whole slide images (WSI) have been used in many pathology applications such as teleconsultation, teaching and research, but not in primary diagnostics. The aim of this study was to test the feasibility of using WSI in primary diagnostics of paediatric pathology specimens and placental tissue.

Materials and methods Eighty consecutive tissues biopsies and resections from patients under 18 years old were selected, as well as 20 placentas. These cases had been diagnosed in the year 2009 by a single pathologist. The same pathologist who had performed the original diagnosis based on light microscopy was asked to rediagnose these 100 cases on WSI scanned at 20× magnification as well as by light microscopy having the original clinical information available, but blinded to the original light microscopic diagnoses. The original diagnoses were compared with WSI based diagnoses and rediagnoses by light microscopy and classified as concordant, mildly discordant (without clinical consequences) and discordant (with clinical consequences).

Results The original diagnoses were concordant with WSI and light microscopic diagnoses in 90% and 93% of cases respectively, which was not significantly different. Digital reassessment yielded eight mild discrepancies and two discrepant cases (2%) where the difference in diagnoses could have clinical implications for the patient. Light microscopic reassessment showed seven mild discrepancies. It turned out to be difficult to identify nucleated red blood cells on WSI, even when scanned at 40×.

Conclusions Primary diagnostics of paediatric tissue biopsies and resections can generally well be done on WSI. However, some difficulties were encountered in examining placenta tissue where the identification of nucleated red blood cells may need higher resolution or even scanning at multiple focus depths, which is well possible on most current slide scanners.