December 2012

Case A

open in AAPSP Digital Slide Server


12 year old bitch with walnut sized, irregularly nodular mass in the hind mammary gland.

Assessor’s Comments

The responses demonstrate that histopathology of mammary masses is a tricky area of veterinary pathology.  Four respondents said the mass was benign (complex adenoma (adenomyoepithelioma) x 3, fibroadenoma x 1) and 8 said malignant (adenocarcinoma x 4, complex carcinoma grade I x 3, tubular carcinoma grade II x 1). Most said or implied they used the Pena grading system1. Grading in this system is based on tubule formation, nuclear pleomorphism and mitotic rate. Responses usually reported dominant tubule formation, varied somewhat in the extent of pleomorphism and varied widely in observed mitotic rate. Two respondents did not report a mitotic rate. Given that all participants examined the same slide, the variation in observed mitotic rate is a little surprising. However, the appearance of mammary tumours is known to vary within the tumour mass.

The prognostic usefulness of these reports, taken as a group, would be confusing and of limited value to a clinician. The dog, a 12-year-old Rhodesian Ridgeback, has had no local recurrence (or distant metastases) at 6 months post-surgery.

1. Goldschmidt M et al, Classification and Grading of Canine Mammary Tumors. Veterinary Pathology 48(1) 117-131.


Case B

open in AAPSP Digital Slide Server


Emperor tetra in an aquarium developed abdominal swelling and irregular swimming behaviour.

Example Histopathological description

The slide is a parasagittal section of a small fish approximately 2.4 x and includes the head, body, gills and coelomic cavity. Several abdominal organs, including the anterior and posterior kidney, spleen, intestine and mesentery plus the coelomic wall, are expanded and in some cases effaced by abundant multifocal to coalescing granulomas. Other abdominal organs including the liver and swim bladder are displaced. Granulomas vary in size up to 2 mm in diameter but most are 50 to 300 µm in diameter. They often have a central core of eosinophilic or necrotic material surrounded by a mixed cell population of macrophages, lymphocytes, heterophils and fibroblasts. There is a variable amount of peripheral fibroplasia. In the core of some granulomas are multiple small (approx. 10 µm) clear to basophilic stippled irregular bodies. Anterior gill lamellae have small focal accumulations of macrophages and lesser numbers of granulocytes.

Morphological Diagnosis

1.  Nephritis, splenitis, enteritis and coelomitis, granulomatous, chronic, severe and extensively multifocal to coalescing.

2.  Branchitis, histiocytic, chronic, mild, focal.


Piscine mycobacteriosis

Differential Diagnoses

Neon tetra disease (caused by the microsporidian Pleistophora hyphessobryconis), other microsporidia and myxosporidia, fungi and other bacteria such as nocardia.