September 2015
Case A
History
Tissue from a six-year-old male neutered cat with a mass on its abdomen
Example Histopathological Description
This is a section of haired skin with dermis and subjacent subcutis extensively and diffusely infiltrated by faintly basophilic spindle-shaped mesenchymal cells with prominent nuclei, coarse chromatin patterns, prominent nucleoli and indistinct cell margins and other features of malignant neoplasia including mitoses (including bizarre forms) which are present in low to moderate numbers. Mature dermal collagen bundles are intimately invested with these cells, which appear to have cut smoothly through and isolated stromal components, including adipocytes and blood vessels as well as collagen, thus forming irregular, inter-anastomosing, mostly empty spaces lined by the infiltrating cells in the manner of endothelium. In places the infiltrates are semi-solid, and elsewhere have invaded vein walls and apparently initiated thrombosis. There are minor aggregations of leucocytes in some tissue spaces, but inflammation is not a feature and haemorrhage is minimal. There are scattered pigment deposits that are consistent with haemosiderin.
The specimen was not inked before processing, so excision lines cannot be conclusively identified, but some edges of the block are consistent with excision lines, and the malignant cells extend right up to these margins.
Morphological Diagnosis
Feline ventral abdominal cutaneous angiosarcoma (lymphangio-sarcomatous variant). Incompletely excised.
Comments
Malignant endothelial tumours whose vascular spaces contain abundant blood tend to be called haemangiosarcomas, even when a considerable proportion of them are solid. Angiosarcomas that are not suffused with blood were once called lymphangiosarcomas because they were assumed to be derived from lymphatic endothelium, which has less propensity for vascular invasion and whose chambers consequently contain more lymph than blood. However, the term lymphangiosarcoma has been replaced by angiosarcoma, since there is in some cases much overlap in morphology.
Feline ventral abdominal angiosarcoma has been reported by Hinrichs U, et al: Lymphangiosarcomas in cats: A retrospective study of 12 cases. Vet Pathol 36:164- 167 (1999). Nine of the reported cases involved the ventral abdominal skin. This case was the subject of AFIP Conference 19 (2003) see http://www.askjpc.org/wsco/wsc/wsc02/02wsc19.pdf.
The most distinctive feature of this case was the relative lack of erythrocytes and plasma within the inter-anastomosing spaces of the tumour. The vascular spaces in most angiosarcomas contain more blood than did this example, presumably because of their propensity to break into blood vessels, so the lack of free blood in this case was worthy of emphasis.
The morphological feature that is most characteristic of the malignant endothelial tumours is the ease with which these cells invade mature collagen and other tissue components. There is good evidence that this phenomenon is the result of expression and activity of matrix metalloproteinases.
A prominent feature of this case was the manner in which the infiltrate had isolated individual adipocytes in the subcutis.
September 2015
Case B
History
An adult male horse with bloody purulent nasal discharges and multiple, firm, whitish, nodules and ulcers on the nasal conchae, nostrils and upper lip.
Example Histopathological Description
This specimen of nasal concha appears to have been fixed in an acidic fixative such as Bouin’s fluid, judging by the degree of red cell lysis and the amount of pigment consistent with acid haematin. To one side of the cartilage core, the submucosa is greatly thickened by proteinaceous oedema, by copious infiltrates of mixed inflammatory cells including many degenerate polymorphs, and by numerous large blood vessels, the majority of which appear to be veins distended by thrombi, many of which contain masses of degenerate leucocytes. Some thrombi are recanalised. The respiratory epithelium is largely intact on both sides but is diffusely eroded and somewhat degenerate on the more inflamed side; some of this; however, may be handling artefact.
Morphological Diagnosis
Rhinitis; pyogranulomatous, severe, diffuse, subacute, with extensive multifocal thrombosing pyogranulomatous vasculitis.
Aetiological Diagnosis
Burkholderia mallei rhinitis (Glanders)
Comment
This was a case in the AFIP Wednesday Conference 24 of 1999 (http://www.askjpc.org/wsco/wsc/wsc98/98wsc24.htm).