VETERINARSKI ARHIV 68 (1), 27-32, 1998

Colonic fibroma and fibroleiomyoma in a horse

Azizollah Khodakaram Tafti, Ahmad Oryan*, and Mohsen Maleki

Pathology Department, Veterinary School, Shiraz University, Shiraz, Iran

* Contact address:
Dr. Ahmad Oryan,
Pathology Department, School of Veterinary Medicine, Shiraz University, 71365 Shiraz, P.O. Box 611, Iran

ISSN 0372-5480
Printed in Croatia

KHODAKARAM TAFTI, A., A. ORYAN, M. MALEKI: Colonic fibroma and fibroleiomyoma in a horse. Vet. arhiv 68, 27-32, 1998.


The carcass of a six-year-old male horse with a history of acute colic and consequent death was presented for pathological examination. At necropsy, two tissue masses were observed, one on the serosal and the other in the submucosal layer of the small colon. Histological examination of the mass on the serosal layer revealed a tumour composed of oval spindle-shaped cells that was diagnosed as a fibroleiomyoma. The mass in the submucosal layer consisted of irregular connective tissue and fibroblasts characteristic of a fibroma.

Key words: fibroma, fibroleiomyoma, histological examination, colic, horse


Tumours of the alimentary tract are rare in the horse and is reported to constitute 3.2% of horse tumours (BAKER and LELYLAND, 1975; HEAD, 1990). Unlike the common occurrence of some tumours such as stomach carcinoma, intestinal leiomyoma and lymphosarcoma, some tumours, such as fibroma and fibroleiomyoma, are not reported from the intestinal tract of the horse. The occurrence of intestinal leiomyoma has been reported by several authors (RAMAKRISHNA et al., 1971; COLLIER and TRENT, 1983; HANES and ROBERTSON, 1983; RAMEY and REINERSTON, 1984). Mesenchymal intestinal tumours such as fibroma and fibroleiomyoma occur very rarely and there are few reports of their occurrence in the dog (JUBB et al., 1993). This report describes the pathological features of fibroma and fibroleiomyoma observed in the small colon of a six-year-old, thoroughbred male horse with a history of acute colic which did not respond to symptomatic therapy with hyosine and dipyrone. It is believed to be the first report of such a tumour in the horse.

Materials and methods

A six-year-old, thoroughbred male horse provided material for this study. Tissue samples collected at necropsy were fixed in 10 per cent neutral buffered formalin, processed by standard techniques, and 5 祄 sections were stained with haematoxylin and eosin, Van Gieson, green Masson trichrome and blue Masson trichrome.


Post-mortem examination revealed lesions indicative of severe shock, such as shock lung or congestive atelectasis, presence of blood-tinged fluid in the intestine or visceral pooling, mild acute tubular necrosis in the kidneys, sludging and formation of chicken fat clot and disseminated intravascular coagulation, and a firm mass of 8󬱜 cm dimensions and 110 g mass on the serosal surface of the small colon, as well as another mass of 10󭅊 cm dimensions and 215 g mass in the submucosal layer which projected into the lumen of the small colon, causing partial obstruction. The colon luminal diameter was reduced and the portion proximal to the lesions was dilated and had a thinner wall. Remaining the organs were grossly normal.

Macroscopically, the mass on the serosal layer was round with multiple secondary focal nodules being confined on its surface area (Fig. 1). The mass was white to yellow in colour and showed a firm consistency. The underlying muscular layer of the intestine was hypertrophic, with a thickness of about three times that of the normal layer. The mass in the submucosal layer was round, white to grey in colour with a firm consistency. This mass was isolated from the surrounding tissues and projected into the intestinal lumen (Fig. 2).

Fig. 1.

Fig. 1. The fibroleiomyoma on the serosal layer of the small colon with multiple secondary focal nodules (arrows)

Fig 2.

Fig. 2. Cross-sectional area of both tumours. The fibroleiomyoma is located on the serosal (large arrow) and the fibroma in the submucosal layer (small arrow). The mucousal layer covering the fibroma is intact and the muscular layer between the two tumours is hypertrophic (arrow head).

Fig 3.

Fig. 3. Photomicrograph of fibroleiomyoma. The tumor is composed of sheets and bundles of oval and spindle- to cigar-shaped cells with eosinophilic cytoplasm (arrows). H&E, 250.

Microscopically, a mixture of fibroblasts, myocytes, collagen fibers and muscle fibers were observed in the sections from the mass on the serosal layer. The oval, or elongated to cigar-shaped, myocytes were distributed between collagen fibers. Elongated spindle-shaped fibroblasts and fibrocytes were also present among the disorganised, haphazard connective tissue fibers (Fig. 3). The tumour was encapsulated. This mass was diagnosed as being a fibroleiomyoma by van Gieson, green Masson trichrome and blue Masson trichrome. However, the mass in the submucosal layer, covered by an intact colonic epithelial layer, was made up of disorganised collagen, fibroblasts, and elongated fibrocytes (Fig. 4), was diagnosed as a fibroma. No inflammatory reaction was present in the tissue sections. Both tumours were well vascularised and did not show signs of malignancy.


To date, there has been no reports on the occurrence of fibroma and fibroleiomyoma in the horse intestine. However, due to the presence of mesenchymal tissues in the alimentary tract, their occurrence does not seem impossible. The most common tumours of the horse alimentary tract reported so far are stomach carcinoma and lymphosarcoma (PASCOE, 1982). Other reported tumours include adenocarcinoma (KERR and ALDEN, 1974; COTCHIN, 1977; HONNAS et al., 1987; ROTTMAN and ROBERTS, 1991), rectal myoma (COTCHIN and SMITH, 1975), duodenal adenoma (DAMODARAN and THANIKACHALAM, 1975), colonic neurofibroma and intestinal reticulosarcoma (COTCHIN and SMITH, 1975; PASCOE, 1982), duodenal leiomyosarcoma (MAIR et al., 1990), and rectal leiomyosarcoma (CLEM et al., 1987).

Fig 4.

Fig. 4. Photomicrograph of the fibroma. The tumour is composed of unorganised haphazard connective tissue (arrows). H&E, 200.

Colic was the most frequent sign of presence in those animals, where tumours arose from the wall of the intestinal tract. In the present case, the tumours appear to have arisen from the connective and muscular tissues of the intestinal wall. These tumours caused narrowing of the lumen and difficulty in passage, which was clinically expressed as colic.

Although localised intestinal tumours such as fibroma and fibroleiomyoma are uncommon, they should be considered in the differential diagnosis of horses showing signs of colic due to partial intestinal obstruction, and if present the potential for the successful surgical management of such cases should be considered.

We thank Dr. M. Moulaei for referring the case and supplying relevant clinical data, as well as B. Shourangiz for his technical assistance.


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Received: 7 October 1997
Accepted: 12 January 1998

KHODAKARAM TAFTI, A., A. ORYAN, M. MALEKI: Fibrom i fibrolejomiom kolona u konja. Vet. arhiv 68, 27-32, 1998.


Razudeno je truplo sestogodisnjeg konja uginulog nakon akutne kolike. Pri razudbi su pomno pretrazene dvije tvorevine, jedna na seroznom, a druga u submukoznom sloju maloga kolona. Histoloskom pretragom tvorevine na seroznom sloju ustanovljen je tumor sastavljen od jajastovretenastih stanica i dijagnosticiran kao fibrolejomiom. Masa u submukoznom sloju sastojala se od nepravilnog vezivnog tkiva i fibroblasta osebujnih za fibrom.

Kljucne rijeci: fibrom, fibrolejomiom, histolosko istrazivanje, kolika, konj