Histological observations on aural fibrosarcoma in a Holstein cow

Abstract Fibrosarcomas occur as a mesenchymal tumour of malignant fibroblasts in a collagen background and are usually found in the female genital organs and rarely involve the skin. A 5‐year‐old female Holstein cow with a raised mass at the base of right ear was referred. On gross examination, the mass was approximately 13.00 × 10.00 × 7.00 cm in size. Finally, complete surgical removal was selected. The mass was encapsulated and the dermis was expanded by spindle‐shaped to polygonal neoplastic cells. These cells were arranged in interwoven pattern. Mitotic figures were infrequent. Masson's trichrome demonstrated the positive and blue staining of collagen. Immunohistochemically, the sections were uniformly positive for Vimentin and negative for Desmin, SMA and GFAP. A well‐differentiated fibrosarcoma was diagnosed based on histopathological features. Surgical excision is the treatment of choice for this neoplasm. In the present case, surgery was also performed successfully and no new growth of the mass was observed 4 months following the surgical procedures. To our knowledge, this is the first report of well‐differentiated fibrosarcoma in a Holstein cow.


INTRODUCTION
Fibrosarcomas are malignant connective tissue tumours with immature proliferating fibroblasts or undifferentiated anaplastic spindle cells arranged in interwoven pattern (Hendrick, 2017). These tumours have been reported in cats (Strong et al., 2016), dogs (de Paula et al., 2021) and horses (Bass et al., 2017). There are only rare reports of bovine vaginal (Avci et al., 2010;Mushap, 2016), penile (Hesaraki et al., 2010), mandibular (Braun et al., 2001) and mammary gland fibrosarcoma (with metastases in local lymph nodes) (Orr, 1984) in the literature. Bovine cutaneous fibrosarcoma is an unusual tumour. To our knowledge, there has been no report of this tumour in the Holstein cow.
This paper is about the macroscopic, surgical and histopathological findings of aural well-differentiated fibrosarcoma in a Holstein cow.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2023 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.

CASE DESCRIPTION
In December 2021, a 5-year-old female Holstein cow with a raised mass at the base of right ear was referred (Figure 1a and  Germany) and stained with Haematoxylin and Eosin. Sections were examined using a light microscope (E600; Nikon, Tokyo, Japan) and representative images were taken. The formalin-fixed mass sections were also stained with Masson's trichrome (Luna, 1968). For this reason, the sections (5 µm) were deparaffinised, rehydrated and wash. Based on owner information, no new growth of the mass was observed 4 months following the surgical procedures (Figure 1d).

DISCUSSION
Fibrosarcomas are common tumours in domestic animal species, and can range from well differentiated to more aggressive, but metastasis is uncommon (Hendrick, 2017). and BPV-8) have been isolated from fibroepithelial tumours (fibropapillomas) in cattle (Silva et al., 2013). Fibropapillomas are the most common bovine cutaneous tumours. Fibrosarcomas, unlike fibropapillomas, are rare (Silva et al., 2013). In cattle, Fibrosarcomas occur as a mesenchymal tumour of malignant fibroblasts in a collagen background and are usually found in the female genital organs (Avci et al., 2010). To our knowledge, cutaneous fibrosarcoma has not been reported in Holstein cow. Similar to this case, mostly fibrosarcomas develop in adult animals (Hendrick, 2017). There is significant overlap between fibrosarcomas and leiomyosarcomas in histopathological findings. Microscopically, unlike fibrosarcomas, leiomyosarcomas have elongate nuclei, with blunt rounded ends and eosinophilic cytoplasm.
However, histochemical and immunohistochemical identification are essential for an accurate histopathological diagnosis. In this case, on Masson trichrome staining, spindle cells with red cytoplasmic stain were not found among the blue collagen bundles. The mass was also stained negative for Desmin and SMA. So, these results revealed that this tumour could not originate from muscle cells. Unlike this case, positive IHC reactivity for smooth muscle actin and Desmin is supportive of a leiomyosarcoma (Hendrick, 2017;Roccabianca et al., 2020).
The aural mass was not schwannoma because of its negative reactivity to GFAP (Hesaraki et al., 2010). This case is a fibrosarcoma with a reaction only to Vimentin. Surgical excision is the treatment of choice for well-differentiated fibrosarcoma (Hendrick, 2017). Deltapapillomavirus (BPV-1 and BPV-2), Epsilonpapillomavirus  and genetic influences are included as potential factors for fibropapilloma (Silva et al., 2013). E5, the major BPV oncoprotein, is expressed in the basal layer of the epidermis and in dermal fibroblasts (McCance, 2002), during the early and late stages of viral carcinogenesis, suggesting that E5 is causally involved in the development of the bovine cutaneous tumours (Silva et al., 2013). However, we were unable to identify an obvious etiological agent, and the cause of the fibrosarcoma in this Holstein cow remains unknown.

CONCLUSION
The present study revealed that diagnosis of fibrosarcoma in a quite rare localisation by the routine histopathological staining method (HE) may be difficult. So, concurrent evaluation of both histopathological and IHC features is required for the definitive diagnosis of this tumour.