Aims: Digital pathology (DP) offers advantages over glass slide microscopy (GS), but data demonstrating a statistically valid equivalent (i.e. non-inferior) performance of DP against GS are required to permit its use in diagnosis. The aim of this study is to provide evidence of non-inferiority. Methods and results: Seventeen pathologists rereported 3017 cases by DP. Of these, 1009 were re-reported by the same pathologist, and 2008 by a different pathologist. Re-examination of 10 138 scanned slides (2.22 terabytes) produced 72 variances between GS and DP reports, including 21 clinically significant variances. Ground truth lay with GS in 12 cases and with DP in nine cases. These results are within the 95% confidence interval for existing intraobserver and interobserver variability, proving that DP is non-inferior to GS. In three cases, the digital platform was deemed to be responsible for the variance, including a gastric biopsy, where Helicobacter pylori only became visible on slides scanned at the 960 setting, and a bronchial biopsy and penile biopsy, where dysplasia was reported on DP but was not present on GS. Conclusions: This is one of the largest studies proving that DP is equivalent to GS for the diagnosis of histopathology specimens. Error rates are similar in both platforms, although some problems e.g. detection of bacteria, are predictable.

In a 12-month prospective study incorporating four neighbouring district general hospitals, 228 patients required a total of 236 admissions with intestinal obstruction. The aetiological factors included adhesions 75 (32 per cent), malignant disease 61 (26 per cent), strangulated hernias 59 (25 per cent), volvulus 10 (4 per cent), acquired megacolon 6 (3 per cent), pseudo-obstruction 4 (2 per cent), faecal impaction 6 (3 per cent) and miscellaneous 15 (6 per cent). The peak incidence for obstruction due to adhesions, malignant disease and strangulated hernias each occurred in the eighth decade. Surgery was performed within 48 h of admission in 29 per cent adhesive obstructions (22), 30 per cent obstructions due to malignant disease (18) and 68 per cent strangulated hernias (40)--bowel resection rates in these three groups were 13.5, 50 and 29 per cent, respectively. The overall mortality was 11.4 per cent (26 deaths) and postoperative mortality was 12.3 per cent (19 deaths). During the 12-month study period, 228 patients required a total of 2993 inpatient hospital days as a result of intestinal obstruction. Postoperative adhesions have become the commonest cause of intestinal obstruction but strangulated hernias and intra-abdominal malignant disease still account for 50 per cent of all cases and mortalities. Obstruction due to strangulated hernias and intra-abdominal malignant disease typically occurs in the elderly age group where a more aggressive policy of elective surgical intervention is likely to be associated with increased postoperative morbidity and mortality.

We have audited the frequency of use and outcome of the "equivocal/atypia probably benign" (C3) and "suspicious of malignancy" (C4) category for breast cytology in our Unit. A total of 14 935 cytological specimens were reported by at least one of the three pathologists with a special interest in breast pathology, according to five categories of the NHSBSP guidelines for cytology reporting, 1992; 3.7% (555 cases) and 3.9% (587 cases) of cases were classified as equivocal (C3) and suspicious (C4), respectively, giving a total rate (C3 + C4) of 7.6%. Of the C3 cases, 68% were subsequently benign and 32% were malignant. Of the C4 cases, 19% were subsequently benign and 81% malignant. The commonest benign lesions in both categories were fibroadenomas (7.6% of C3 and 19.8% of C4), fibrocystic change (14.3% of C3 and 12.5% of C4), radial scars (6.2% of C3 and 10.4% of C4) and papillomas (6.2% of C3 and 6.3% of C4). Of the malignant lesions (particularly those classified as C3), a high proportion were low grade or special type cancers. The categories of atypia probably benign (C3) and suspicious of malignancy (C4) in breast cytology provide a strategy for classification of problematic or uncertain cases; this maintains the predictive value of the benign (C2) and malignant (C5) categories, and allows separation of these difficult cases into clinically useful groups with differing probabilities of malignancy.

Objective To determine the relative prognostic importance of microvascular invasion in apparently localized renal cell carcinoma (RCC

RESULTSMitomycin C instillation was followed by ALA concentrations of 6%, 8% or 10%; there was no effect on toxicity. The light dose, at a wavelength of 635 nm, was increased from zero to 25 J/cm 2 , with the upper fluences producing transient symptoms. There were no episodes of skin photosensitivity or systemic toxicity. A total fluence of 25 J/cm 2 represented the upper light dose for the tolerability of this procedure by patients. There were no persistently high urinary symptom scores or reduction in functional bladder capacity up to ≥ 24 months of followup. In this group, cumulative tumour recurrences were none at 4, two at 8, six at 12, nine at 18 and 11 at 24 months after PDT, respectively. CONCLUSIONSequential mitomycin C and ALA-PDT is a safe and well tolerated treatment, with potential for managing difficult-to-control superficial transitional cell carcinoma and carcinoma in situ of the bladder .