Abstract
This volume is part of the series updating the classification of canine and feline tumors that was first published as part of the World Health Organization (WHO) International Classification of Tumors of Domestic Animals in 1974 and 1976. This monograph is one of 12 that will be published in the second series. The monograph is organized into an Introduction, a tabulated Histological Classification scheme, Definitions and Explanatory Notes, References, Figures, and an Index. The Introduction discusses the authors' approach to diagnosis and classification. As in the previous WHO volume, the approach is to use “descriptive morphology” as the basis for classification, arguing that the histogenetic classifications are too uncertain with respect to the origin of specific cell types. A real strength of the new classification is the incorporation of prognostic factors. In the dog, this information is based on a series of statistical studies of the prognostic significance of tumor and host characteristics.
The classification schemes are fairly straightforward; however, canine mammary tumor classification especially is controversial, and other schemes have been proposed. Appropriately, the canine malignancies are organized in order of increasing malignancy, based on prognostic data; those in the cat are not organized in this way because of the lack of comparable data in queens. The italicized definition for each classification is a nice touch and useful, but the description that follows is often too brief, and the volume would have benefitted from more detail here, especially for readers such as pathology trainees who are not familiar with many of the lesions. In the Preface and in the text, it is noted that “the WHO histological classification of tumors in man was followed as closely as possible” to “facilitate communication between veterinary and medical pathologists.” This is a laudable goal and the authors are to be commended for it; however, some terms have been carried over that are vague and not descriptive of the lesions seen. Two of those terms are epitheliosis and adenosis. Epitheliosis, as used, appears to be a synonym for diffuse or multifocal epithelial hyperplasia within ducts or ductules. Although this phrase is wordier than epitheliosis, it is certainly more accurate and descriptive. The term adenosis is similar. For example, Fig. 32 shows an example of “lobular hyperplasia, adenosis, simple type.” The “adenosis” adds nothing to the diagnosis and “lobular hyperplasia, simple type” would be enough. The one place where the use of adenosis might be warranted is for comparison with sclerosing adenosis, a common lesion in women, although this condition is not commonly diagnosed in dogs or cats. There are other places where there are inconsistencies. On page 13, it is stated that the authors do not use the terms duct or ductular carcinomas that have been proposed by others. On page 24, under section 4.1 “Ductal hyperplasia,” it is stated that “distinction from intraductal carcinoma may be very difficult.” In Fig. 30, the caption “Merging of ductal hyperplasia and intraductal carcinoma …” suggests that intraductal carcinoma is arising from an area of hyperplasia. Given this, it is puzzling why the classification scheme does not include a category of ductal or intraductal carcinoma and just what the authors mean here.
One difficulty with the format (as it was with the earlier WHO format) is that the figures are grouped away from the descriptions, making for excessive page turning to compare the written description with the photomicrograph of each lesion. In general, the photographs are of good quality. Some photographs (e.g.,Fig. 9, 16, and 18) are at too low magnification and do not adequately show the details of the lesions. The use of color in a number of figures is to be applauded.
The authors have tackled a difficult and controversial topic, and although their classification may not be accepted by all, the prognosis-based classification of canine mammary tumors makes this volume a useful adjunct for the practicing veterinary pathologist.