Routine morphometrical analysis can improve reproducibility of dysplasia grade in Barrett's oesophagus surveillance biopsies

Abstract

Background: The grade of dysplasia found in Barrett's oesophagus surveillance biopsies is a major factor to determine follow up and treatment. However, it has been reported that the reproducibility of the grading system is not optimal.

Aims: To compare routine and expert dysplasia grades in Barrett's oesophagus surveillance biopsies. To evaluate prospectively morphometrical grading support and to assess the pitfalls in its daily application.

Methods: Consecutive biopsies (n = 143) were graded routinely by experienced general surgical pathologists as no dysplasia (ND), indefinite for dysplasia, low grade dysplasia (LGD), and high grade dysplasia (HGD). Two expert gastrointestinal pathologists blindly reviewed all sections. The stratification index of nuclei, mean nuclear area, and Ki67area% were assessed routinely according to a strict protocol. With these features, the previously described morphometrical grade was calculated for each case. The grades provided by the experts, surgical pathologists, and morphometry were compared.

Results: The general pathologists graded many more cases as dysplastic than did the experts. Complete agreement between the experts' grades and the original grades was 50 of 143 (35%). Sixty four of the 71 original LGDs and 11 of the 23 original HGDs were downgraded by the experts, whereas one LGD was upgraded. In 93 of the 143 biopsies, at review pitfalls or special characteristics of a technical nature (tangential cutting, severe inflammation, ulcer or the squamocylindrical junction very close by, among others) were seen in the part of the biopsy marked as diagnostic. These probably contributed in part to the original overdiagnoses and could have been prevented or corrected. The morphometrical grading model has not been developed to compensate for this; application of the current morphometrical grading method is not allowed and may result in erroneous (usually too high) morphometrical grades. In spite of this, all HGDs according to the experts were recognised as such by morphometry, also in these technically less adequate sections or areas. However, 46% of the experts' downgrades occurred in technically adequate sections and thus were caused by a difference in interpretation. Here, morphometrical support proved to be useful because, in agreement with the experts, it downgraded 51% of the original LGDs, upgraded one of eight NDs to LGD and one of 39 LGDs to HGD.

Conclusions: Experts downgraded a high proportion of biopsies graded as LGDs and HGDs by the surgical pathologists. Morphometrical grading can be used for daily quality control; the results were close to those of the experts and corrected a large number of cases erroneously graded by surgical pathologists.

Figure 1

Illustration of an important pitfall causing overdiagnosis: tangentially cut normal biopsies erroneously classified as low grade dysplasia (LGD). (A) Normal mucosa; SUP, superficial part; DEEP, deep proliferating part; MM, muscularis mucosae; MIT, mitoses. (B) As a result of retraction of the muscularis mucosae, the originally flat biopsy is bent as illustrated. Thus, a horizontal section at line 1–1′ will reveal the microscopic image seen below. (C) Schematic drawing of the microscopical image of a section taken at 1–1′. From left to right, a rim of superficial glands is seen, then a very large proportion of the section consists of basal glands with somewhat larger nuclei than in the superficial layer, plus mitotic activity, and then again a small rim of superficial glands. The muscularis mucosae is lacking. Because of the large proportion of (somewhat darker stained) basal glands with numerous mitoses and because the nuclei are larger than in the superficial layer, in contrast to the superficial glands, these basal glands give the false impression of “atypical” glands, and hence are overgraded as LGD.

Figure 2

Scatterplot of the stratification index and the Ki-67 area% versus the original grades in the total study material of 143 cases. Note the overlap between the no dysplasia (ND) and low grade dysplasia (LGD) biopsies. However, the high grade dysplasia (HGD) biopsies are well discriminated by the morphometrical features.

Figure 3

Scatterplot of the stratification index and the Ki-67 positive area% in the 64 adequate biopsies. The decision lines of no dysplasia (ND) versus low grade dysplasia (LGD) and LGD versus high grade dysplasia (HGD) are according to Sandick et al (compare also with table 4). See text for comments on the case misclassified on the original diagnosis (arrow).

Figure 4

Three dimensional scatter plot of the three morphological features of the original diagnoses of no dysplasia (ND), low grade dysplasia (LGD), and high grade dysplasia (HGD). The LGD case (arrow) classified as HGD both by the experts and by morphological grading not only has high stratification index (SI) and Ki-67 positive area% values, but also has a high mean nuclear area (MNA). Thus, morphometrically, this lesion is clearly in the range of the HGDs (in agreement with the experts’ diagnosis).