Congenital desmoid fibromatosis in a Holstein heifer

Abstract

An 11-month-old, Holstein heifer was presented for a progressive swelling on the left side of the face that had been present since birth. A diagnosis of fibromatosis was made, based on macroscopic and microscopic examination of the abnormal infiltrative tissue. Because of the poor prognosis the animal was euthanized.

An 11-month-old, Holstein heifer was admitted to the Centre Hospitalier Universitaire Vétérinaire of the Université de Montréal for a progressive swelling on the left side of her face that extended from the base of the horn towards the eye. According to the owner, the swelling had been present since birth. The mass had been growing since birth. The animal was eating well and growing normally when compared with herd mates. The skin over the mass had always been intact. The animal was referred because the swelling was becoming more evident.

Case description

Upon presentation, the heifer was bright and alert. Except for the swelling of the left portion of the face, results from the physical examination were within normal limits. The swelling extended rostrally from caudal to the base of the left ear to the level of the premolars, ventrally from dorsal to the orbit to ventral to the mandible. On palpation, a fluctuant, yet firm, mass was felt. The skin was intact and on palpation the mass appeared to be subcutaneous. A 4-cm diameter hard mass was palpated just caudoventral to the left eye. At this point, the differential diagnoses were a tumor, a congenital anatomic abnormality, or an abscess. A blood sample was submitted for a complete blood (cell) count and chemical profile, the results from which were within reference intervals. Radiographic images of the head showed soft tissue swelling on the left side with some mild calcification near the left orbit. The bones of the skull appeared to be normal. Ultrasonographs of the mass were obtained with a 7.5 mHz linear probe and showed that the mass was homogeneously echoic with a thickness of approximately 6.5 cm (digital calliper) in certain areas. Fine-needle aspirates were obtained at multiple sites of the mass, but cytologic examination was inconclusive. Biopsy with a biopsy needle (Tru-Cut 14G 3 15 cm, Cardinal Health, McGaw Park, Illinois, USA) was attempted, but the amount of tissue harvested was inadequate for evaluation. The site was then prepared for surgery and lidocaine (Lurocaine; Vetoquinol N-A, Princeville, Québec) was infiltrated locally. A 3-cm skin incision was made over the mass, and a skin punch biopsy (Miltex,York, Pennsylvania, USA) was used to harvest a sufficient amount of tissue for further analysis. The skin was closed with polydioxanon 2-0 (PDS II Ethicon, Johnson & Johnson, Markham, Ontario) in an interrupted cruciate fashion. The biopsied material was submitted for histopathologic examination, which showed that the mass was compatible with fibromatosis. Fibromatosis is treated by wide excision, including a margin of adjacent normal tissues. Because of its locally aggressive behavior, the chance of recurrence (1,2), the possibility of peripheral nerve damage during surgery, and for cosmetic reasons, a poor prognosis was given and euthanasia was strongly suggested to the owner.

At necropsy, the mass observed clinically on the left side of the head was grossly whitish pink, moderately soft, fibrous-like, and poorly circumscribed. It was not attached to the skin, except in a few areas where it seemed to have infiltrated the panniculus. Laterally, the mass appeared as a fibrous thickening centered on the superficial fascia of the masseter muscle. It extended caudally to the caudal border of the mandible and rostrally to the rostral aspect of the malaris muscle (Figure 1). The mass was focally adherent to the parotid lymph node and parotid gland. It also extended between the left eye and ear. Within this latter area, the mass reached a maximum thickness of about 6 cm and was infiltrating and replacing the adipose and muscular tissues (Figure 2). On cut section of the masseter muscle, the fibrous-like tissue extended irregularly within the musculature (Figure 3). Melanosis was noted multifocally in some deeply seated fasciae. At the base of the ear, the proliferative fibrous tissue extended to the auricular cartilage on both sides of the ring. There was no evidence of bone involvement on the left side of the jaw or skull. There were no gross lesions in the other organs.

Figure 1.

Left side of the heifer’s head showing a poorly circumscribed mass (between arrows). Dotted line represents the site of the cut section shown on Figure 2.

Figure 2.

Cut section on the lateral aspect of the face showing a whitish fibrous-like mass with its thickest part marked with an asterisk.

Figure 3.

Cut section through the masseter muscle showing thickened fascia (F) and obvious fibrous-like infiltration within the muscular tissue (arrow).

Histologically, the mass was composed of sheets and bundles of mature and well-vascularized fibrous connective tissue of low to moderate cellularity. The fibroblastic-like cells within the collagenous tissue were oval to spindle shaped and without anaplastic features and mitotic activity. In several areas, the collagenous fibers were spaced from each others by an amorphous and pale acidophilic material. By extension, the proliferative fibrous tissue was infiltrating adjacent tissues, including the skeletal muscles, adipose tissues, some muscular fasciae, the capsule of the parotid lymph node, the capsule and interlobular septae of a portion of the parotid gland, and the base of the external ear (Figure 4). No lesions were observed in any other organs.

Figure 4.

Histological appearance of the facial mass showing proliferating fibrous tissue infiltrating and dissecting adjacent tissues including skeletal muscles (M), adipose tissues (A), and muscular fasciae (F). HEPS stain. Bar = 200 mm. Inset: Close-up of the benign looking fibroblastic cells surrounded by blue-colored collagen fibers. Masson’s trichrome stain.

To further characterize the tumor cells, formalin-fixed and paraffin-embedded tissue from the mass was used for immuno-histochemical staining, using an avidin-biotin-peroxidase complex method (Vectastain ABC Method, Vector Laboratories, California, USA). The tumor cells stained negatively for desmin, smooth muscle actin, and S-100, but strongly positive for vimentin. All of these observations were consistent with a diagnosis of congenital desmoid fibromatosis.

Discussion

The fibromatoses are a group of benign, but locally aggressive, tumors observed occasionally in humans. They have commonly been classified in various subgroups, based on anatomical, biological, and epidemiological features (1,2). One subgroup of fibromatosis, variously called desmoid tumor, musculoaponeurotic fibromatosis, deep-seated fibromatosis, or desmoid fibromatosis, is known to arise from fasciae, aponeuroses, or supporting connective tissue of skeletal muscles (1–4). From a histogenesis viewpoint, these tumors are regarded as neoplasms by most authors, although some consider them as a hyperplastic reaction of connective tissue, possibly initiated by trauma (4). On electron microscopic examination and immunohistochemical staining, they are found to contain fibroblasts and myofibroblasts in varying proportions (1,4). Proliferating cells are vimentin positive and express variable positivity for smooth muscle actin and desmin (1,5). This latter variability may be explained, at least in part, by the maturation of the proliferating cell population from a myofibroblastic phenotype to a fibroblastic/fibrocytic phenotype (6,7). These fibrous proliferations lie in the borderland between fibromas and low-grade fibrosarcomas. On the one hand, they commonly present as large, infiltrative masses that frequently recur after incomplete excision; on the other hand, they are composed of banal well-differentiated fibroblasts that do not metastasize (2,8). In domestic animals, the disorder has been reported rarely and under different names, including fibromatosis, musculoaponeurotic fibromatosis, or desmoid tumor in adult horses (2,7,9), aggressive fibromatosis in a 9-month-old cat (10), and infantile desmoid-type fibromatosis in a 10-week-old puppy (11).

To our knowledge, this is the 1st report of fibromatosis in the bovine species and the 1st congenital case documented in domestic animals. In humans, deep-seated fibromatosis of the desmoid-type often occurs in the musculature of the abdominal wall, although it may be found throughout the body, including the masseter muscles, as in this case (3). The subgroup of desmoid fibromatosis that occurs in early childhood (infantile desmoid fibromatosis) quite frequently arises in the head and neck region, often making adequate surgery impossible and requiring the use of chemotherapy or radiotherapy (1,12,13). In this heifer, successful surgical removal of the fibrous tissue was considered very unlikely, because, at the time of referral, the mass was disfiguring and had reached a large size with no distinct borders.

The clinical, gross, and microscopical findings in this heifer fulfilled the criteria for desmoid fibromatosis. These criteria include: 1) progressive growth with no distinct borders, 2) deep location and relationship to a musculoaponeurotic structure, and 3) the presence of a mature and cytologically benign looking fibrous proliferation that shows evidence of infiltration and replacement of muscle fibers and other adjacent tissues (1–4,9). Early diagnosis of this disorder, followed by radical treatment, will influence the prognosis (2,13).