Diagnostic Report of Multicentric Lymphosarcoma in a Dog

1 Onset and Clinical Symptoms

A dog owner in Jinzhou City, Liaoning Province, kept a small Pug dog, female, over six years old. In late January 2004, it was found that food intake gradually decreased, the dog was depressed, and body weight declined; after supplementation with electrolytes, multivitamins, multi-enzyme tablets, and lactobacillus preparations for treatment, no obvious efficacy was seen. Then treatment with ribavirin, cefotaxime, and roxithromycin also showed no obvious efficacy.

About 3 months after onset, the dog's body weight dropped from 6 kg to 4.3 kg, with physical weakness, difficulty breathing, increased pulse rate, polyuria, and sometimes vomiting. The affected dog's abdominal circumference was markedly increased, visible mucous membranes were pale, and palpation of the abdomen gave a sensation of a firm mass. Hematological examination showed decreased red blood cell count and platelets, and markedly increased lymphocytes and lymphoblasts in the differential white blood cell count. Based on the above examinations, it was initially determined that the dog had solid enlargement of abdominal organs or formation of a mass in the abdominal cavity.

2 Abdominal Exploration and Splenectomy

2.1 Instruments and Supplies The instruments, drugs, and supplies generally required for laparotomy.

2.2 Method The affected dog was restrained in dorsal recumbency and given general anesthesia. On the ventral midline, the small point at the line connecting the xiphoid cartilage and the umbilicus was taken as the midpoint of the incision. The abdominal wall was first incised 3-4 cm, and the abdominal organs were explored with a finger; exploration revealed that the spleen was highly enlarged and firm, and abdominal fluid was increased, red-yellow, and slightly turbid. The ascites was smeared and inoculated onto agar medium, then the ascites was aspirated with a sterile syringe, the incision was enlarged, the spleen was pulled out, the splenic artery and splenic vein were isolated and triple-ligated, cut between the ligatures, then the gastrosplenic ligament and splenorenal ligament were cut, and the spleen was freed and removed. Then, hemostasis was performed on bleeding vessels in the abdominal cavity by compression or suture ligation. However, because the affected dog was highly weakened and anemic, blood coagulability was reduced, and the fragility of abdominal vascular walls was increased, hemostasis was difficult, bleeding was excessive, and before the abdominal cavity could be cleaned and the abdominal wall sutured, the dog died.

3 Necropsy Changes

Necropsy was performed on the affected dog. The main changes were: the spleen was highly enlarged, 26 cm long, with the widest part of the splenic head 9 cm, the splenic tail 7 cm wide, and thickness 3-5 cm; splenic weight 600 g; the splenic capsule was incomplete and uneven, with hemorrhagic foci and necrotic foci, fragile in texture, and the cut surface was mottled gray-white, gray-red, etc., with unclear structural texture; the liver was slightly enlarged, brittle, with small gray-white lesions on the surface, and the gallbladder wall was thickened; the mandibular lymph nodes, inguinal lymph nodes, and mesenteric lymph nodes were swollen, milky white or gray-brown, firm in texture but moist on cut surface, with blurred structure; effusion in the pericardial cavity and abdominal cavity.

4 Bacteriological Examination

Ascites, liver blood, heart blood, splenic blood, and lymph node smears were collected aseptically and inoculated onto ordinary agar medium: smears were stained by Gram staining and Giemsa staining, and examined microscopically after staining. The medium was cultured in a 37°C constant-temperature incubator for 24-72 h.

Observation results: no microorganisms were seen on smear microscopy, and no colonies formed after culture of the medium.

5 Animal Inoculation

5.1 Equipment and Animals Conventional animal inoculation equipment, 30 white mice.

5.2 Pathological Material Liver, spleen, and lymph nodes were taken and made into a pathological material suspension.

5.3 Method The pathological material was divided into two types: pathological material suspension and pathological material treated with double antibiotics. Each was inoculated intraperitoneally into 10 white mice, and another 10 white mice were set as a blank control group, observed for 1 week.

5.4 Results Neither the control group nor the experimental group of white mice developed disease or died.

6 Histopathological Examination

6.1 Materials Spleen, lymph nodes, and liver of the affected dog, 10% formalin, H-E stain (hematoxylin-eosin stain).

6.2 Method The spleen, lymph nodes, and liver of the affected dog were collected according to the requirements for histopathological section materials, fixed with 10% formalin fixative for 24 h, then washed with water for 24 h, then cut into tissue blocks 1 cm x 1 cm x 0.5 cm in size, then subjected to dehydration, clearing, wax immersion, embedding, and sectioning to prepare paraffin sections. The prepared paraffin sections were stained by hematoxylin-eosin staining, and finally mounted and labeled.

6.3 Observation Spleen, lymph node, and liver tissue sections were observed under a microscope at 10 x 20 and 10 x 40 magnification.

6.3.1 Spleen The splenic tissue structure was disordered, the boundary between medulla and cortex was unclear, and lymphoblasts and lymphoid cells were diffusely distributed, especially with denser cell numbers around small arteries and trabecular arteries. The tumor cells had little cytoplasm, and nuclei were oval, round, and quadrilateral, with obvious nuclear membranes, scattered or clumped chromatin, obvious nucleoli, and frequent mitotic figures; reticular cells were rarely seen in splenic tissue, macrophages were occasionally seen, and necrotic foci composed of pink, structureless necrotic tissue of varying sizes were seen in many places.

6.3.2 Lymph Nodes Tumor cells showed diffuse proliferation, and the morphology of the tumor cells was similar to that in splenic tissue.

6.3.3 Liver Tumor cells were mainly distributed around the portal area, and in some places tumor cells were also distributed around the central vein.

7 Diagnostic Results

7.1 The clinical symptoms of the affected dog were emaciation, anemia, and increased abdominal circumference, with a sensation of a firm mass in the abdominal cavity on palpation. Antibiotic treatment was ineffective, and the disease was judged to be a chronic wasting disease.

7.2 Abdominal exploratory surgery and necropsy findings showed that the spleen was highly enlarged, lymph nodes were swollen, and gray-white small lesions were seen in the parenchyma on the liver surface.

7.3 Bacteriological examination and animal inoculation reaction of the affected dog's pathological material were negative.

7.4 Hematological examination showed decreased red blood cell count and platelets, and significantly increased numbers of lymphocytes and lymphoblasts.

7.5 Histopathological examination of lesions in the spleen, lymph nodes, and liver showed proliferation of lymphoblastic tumor cells.

7.6 Based on the above results, the affected dog was definitively diagnosed with multicentric lymphoblastic lymphosarcoma.

8 Discussion

8.1 Canine lymphosarcoma is divided by anatomical site into multicentric type and alimentary tract type, and by tumor cell morphology into lymphoblastic, prolymphocytic and lymphocytic, stem cell, and histiocytic types, among others. This disease is a common tumor in dogs, but it is rarely definitively diagnosed clinically; in this case, through a series of diagnostic methods, we definitively diagnosed multicentric lymphoblastic lymphosarcoma.

8.2 Canine multicentric lymphosarcoma mainly involves the lymph nodes, spleen, and liver, but in this case the prominent manifestation was marked splenic enlargement, which is relatively rare in clinical practice.

8.3 In addition to lymphosarcoma, canine splenomegaly can also be seen in other tumors, tuberculosis, and splenitis, and must be differentiated through histopathological examination combined with other diagnostic methods.

8.4 There is still no effective method for treating canine lymphosarcoma. Prednisone or dexamethasone, cyclophosphamide, chlorambucil, and folate antagonists (such as methotrexate) can be used for treatment, which can relieve symptoms to a certain extent, but overdose of the above drugs can cause poisoning, purpura, fatigue, etc. At this time, medication should be stopped for 10-14 d, and then whether to continue medication should be decided according to the condition; however, it is very difficult to cure, and affected dogs generally have no treatment value.

8.5 Lymphosarcoma is a malignant tumor, and its causes are relatively complex. In terms of prevention, hereditary predisposition should be excluded, daily feeding and management should be strengthened, long-term consumption of and contact with harmful food, drugs, and environments should be avoided, and various chronic diseases should be actively prevented and treated.