Lymphoma in the spinal cord of a mixed-breed feline - case reportABSTRACT
Neoplasms are becoming increasingly prevalent in feline medical practice. This rise has driven the study and growing use of diagnostic and treatment techniques, which are becoming more widely studied and applied in veterinary offices. A significant portion of the feline population is affected by lymphomas, which can develop in various anatomical sites. In this report we describe the case of a mixed-breed feline, 10 years old, negative for retroviruses. The patient presented neurological alterations, including ataxia and paresis of the limbs, as well as a decreased body score. After undergoing complementary ultrasound and radiography exams, no explanation was found for these alterations. Consequently, the cat was referred to a veterinary neurologist. Upon requesting an MRI (magnetic resonance imaging), a mass suggestive of an intramedullary neoplastic process in the C3 and C4 regions was detected. Due to disease progression and the absence of chemotherapy treatment, the outcome was the patient's death. Subsequently, during the necropsy, a lymphoma was confirmed through histopathological examination. Based on this case report, the relevance of advanced complementary exams in diagnostic elucidation is highlighted, as they are essential for defining an appropriate and individualized clinical approach for the patient.
Keywords:
tumor; cat; neurology; neoplasms
RESUMO
As neoplasias estão se tornando cada vez mais prevalentes na clínica médica de felinos, corresponde em alguns países a principal causa de óbito. O linfoma possui alta ocorrência em felinos e é o tipo neoplásico mais observado no sistema hematopoiético de gatos, e são capazes de se desenvolverem em diversos locais anatômicos. O objetivo deste relato é descrever um caso de linfoma intramedular em um felino, com 10 anos de idade, negativo para retroviroses. O paciente apresentava alterações neurológicas como ataxia e paresia dos membros, além de baixo escore corporal, nos exames complementares de ultrassonografia e radiografia, não foi possível justificar tais alterações. Desta forma, na consulta com médico veterinário neurologista foi realizado ressonância magnética, sendo possível detectar uma massa sugestiva de processo neoplásica intramedular na região de C3 e C4. Devido a progressão da doença e falta de adesão ao tratamento quimioterápico, o paciente veio a óbito. Posteriormente, confirmou-se o diagnóstico de linfoma intramedular por meio de exame histopatológico. Com base no presente relato de caso, ressalta-se a relevância dos exames complementares avançados na elucidação diagnóstica, os quais se mostram essências para a definição de uma conduta clínica adequada e individualizada ao paciente.
Palavras-chave:
tumor; gato; neurologia; neoplasia
INTRODUCTION
The evolution of veterinary medicine has led to greater longevity in the lives of small animals, thus, there has been an increase in the incidence of oncological cases, being one of the main causes of death in dogs and cats (Garcia et al., 2009; Oliveira et al., 2019). Among these diseases, malignant lymphoma accounts for 50% to 90% of hematopoietic tumors in feline species (Oliveira et al., 2019; Mello et al., 2019).
Risk factors for feline lymphoma include breed, positive status for feline viral leukemia virus (FeLV) and feline immunodeficiency virus (FIV), as well as environmental influences (Economu et al., 2021). According to Little (2017), these factors predispose to abnormal lymphocyte expansion, along with inflammation of healthy lymphocytes, causing genetic alterations and, consequently, the proliferation of neoplastic lymphocytes. Lymphoma is a type of cancer characterized by the uncontrolled proliferation of malignant lymphoid cells originating in tissues outside the bone marrow. (Siripoonsub et al., 2024)
Lymphomas have several classifications, varying according to anatomical location, cell origin, and histological pattern. They may have origin in lymphoid tissue (nodal lymphoma) or affect other organs (extranodal lymphoma) (Schimidt et al., 2018; Chaves et al., 2024). Regarding the affected site, they may present in multicentric, mediastinal, gastrointestinal, or extranodal forms, with the largest number of cases in felines being in the multicentric and gastrointestinal form (Oliveira et al., 2019). The extranodal form may involve the eyes, kidneys, heart, central nervous system (CNS), among other anatomical sites (Vail et al., 2019).
Central nervous system (CNS) lymphoma can affect the brain, spinal cord, or both, accounting for 14% of extranodal lymphoma cases. Among these, 40% of spinal (epidural) lymphoma cases occur in multiple regions of the spinal cord, with one-third also involving intracranial sites (Marioni-Henry et al., 2008). Spinal lymphoma has been identified in 6.4% of feline lymphoma cases during postmortem examinations (Mello et al., 2019). Therefore, the present study aims to describe a case report of a mixed-breed feline affected by extranodal lymphoma in the spinal cord, emphasizing clinical signs, complementary diagnostic tests, and the outcome of the case.
ETHICAL ASPECTS
This research was not submitted to the Ethics Committee on Animal Use.
CASE REPORT
On July 16, 2023, a female, mixed-breed cat, 10 years old, was presented for clinical evaluation due to a complaint of ataxia. According to medical history, the owner reported that the animal had been previously evaluated at other veterinary clinics and had undergone several additional tests, but without a definitive diagnosis. During previous visits, two rapid tests for feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) were performed, both of which yielded negative results. An abdominal ultrasound was also conducted, revealing changes in the gallbladder and urinary tract, though without clinical repercussions. Radiographic examination of the spine showed no significant abnormalities.
During physical examination, the patient exhibited neuromotor reflexes in all limbs, and normal pupillary reflexes. She was hydrated, with normal mucosal coloration, a body temperature of 37.4°C, a low body condition score, easily palpable ribs, and no signs of cognitive impairment. On gait evaluation, ataxia was evident. A herniated intervertebral disc or spinal cord tumor was suspected, and the patient was referred to a neurological evaluation. A treatment protocol was initiated with gabapentin (15mg/kg) once daily (SID) orally (PO) and prednisolone (0.5mg/kg) twice daily (BID) orally.
On July 17, 2023, the patient was evaluated by a veterinarian specializing in neurology. According to the owner, the clinical condition had worsened, with impaired pelvic limb movement, difficulty accessing the litter box, and selective ingestion of solids and water. On general physical examination, the cat presented a heart rate (HR) of 179 beats per minute (bpm), a respiratory rate (RR) of 60 bpm, 6% dehydration, a capillary refill time (CRT) of 2 seconds, pink mucous membranes, and a rectal temperature of 38.8°C. Neurological evaluation revealed ataxia and tetra paresis, with altered levels of consciousness and proprioceptive deficit in all four limbs. The hopping test revealed a decreased response on the left side, without signs of pain on palpation. The panniculus reflex was present, and cranial nerve abnormalities were not observed. Based on these findings, blood samples were collected for laboratory and imaging tests, including magnetic resonance imaging (MRI). The complete blood count revealed significant alterations; however, biochemical analysis showed decreased serum albumin and total protein levels, which could be attributed to dehydration.
The MRI scan revealed an image suggestive of an intramedullary neoplastic process involving the C3 and C4 cervical spinal vertebrae (Fig. 1A and 1B). Based on these findings, the owners were advised to consult an oncologist to initiate chemotherapy, aiming to improve the clinical condition and achieve a more favorable prognosis. However, the owners opted to continue the current therapeutic protocol. Thus, the treatment with prednisolone (0.5mg/kg, orally, twice daily) and gabapentin (10mg/kg, orally, twice daily) was maintained and showed progressive clinical deterioration, particularly regarding ambulation.
Magnetic resonance imaging of the cervical spinal region. The sagittal section demonstrates spinal cord heterogeneity extending from the C1 vertebra to the thoracic region (A). The dorsal STIR image (B) shows post-contrast enhancement of the spinal cord, with defined and regular borders at the C3 and C4 vertebrae levels (arrow).
Fifteen days later, the animal’s clinical condition worsened, and it unfortunately passed away. To confirm the lymphoma diagnosis, necropsy was performed. Histopathological examination revealed proliferation of small-cell malignant lymphocytes in 80% of the spinal cord segment, associated with pronounced liquefactive necrosis of gray and white matter, as well as Wallerian degeneration of the white matter in the remaining areas. In the thoracic spinal cord segments, neoplastic cells were observed in the meninges and perivascular spaces, findings consistent with primary intramedullary lymphoma (Fig. 2).
Cervical spinal cord segment with brownish discoloration caused by lymphoma (A- arrow). Histological section of the cervical spinal cord showing malignant lymphocyte infiltration, malacia and hemorrhage, stained with hematoxylin and eosin (HE), 10x magnification (B). Malignant lymphocyte infiltrate, HE, 40x magnification (C). Meninges showing malignant lymphocytic infiltrate (arrows), HE, 40x magnification (D).
DISCUSSION
Lymphoma, with its multifactorial etiopathogenesis, is commonly diagnosed in FeLV-positive felines due to the direct activity of the virus on lymphocyte reactivity in the host (Little, 2017). In this report, screening began with immunochromatographic tests to detect or exclude the retrovirus. Two rapid tests were performed, both of which were negative. However, according to Capua et al. (2008), 70% of feline lymphomas are correlated with FeLV. Regardless of this association, there are no barriers preventing retrovirus-negative cats from developing lymphomas later in life.
The relationship between FeLV and lymphoma was particularly emphasized in the study by Mello et al. (2019). In the present study, eight cases of spinal cord lymphoma were diagnosed in FeLV-positive felines, ranging in age from 6 to 96 months. FeLV-infected cats were approximately 62 times more likely to develop lymphoma. In the case report by Oliveira (2019), the patient was not diagnosed with FeLV, despite being presented with the spinal form of lymphoma. This report corroborates the findings described in this case.
Although the number of feline lymphoma cases has increased over the years, only 14% to 25% of cases have been associated with confirmed FELV infection, according to Choy and Bryan (2015). A study conducted in Germany over a period of approximately 30 years demonstrated that the prevalence of lymphoma associated with FeLV infection has decreased (from 59% to 13%), and these findings are consistent with those observed in other regions worldwide (Meichner et al., 2012).
According to Sato et al. (2014), this type of tumor primarily affects older mixed-breed cats, with an average age of diagnosis of 10 years. However, as reported by Nelson and Couto (2015), the age of cats with lymphoma at the time of presentation is bimodal, with the first peak occurring in cats around 2 years of age that are FeLV positive, and a second peak in cats approximately 10 to 12 years old and FeLV negative.
The feline presented with medullary neoplasia; the clinical signs were nonspecific, with only ataxia being observed. Therefore, additional tests were necessary to confirm the diagnosis. No abnormalities were found in the blood counts. This finding is consistent with the literature, as in a study by Gil et al. (2023), involving 89 felines diagnosed with lymphoma, only 23.8% presented with anemia. Another characteristic clearly demonstrated in the study was thrombocytopenia and leukopenia in felines carrying retroviruses, which were not observed in the case described.
An additional test included magnetic resonance imaging (MRI), which, according to Chaves (2024), is the most advanced method for aiding in the diagnosis and localization of the tumor masses. However, it cannot differentiate lymphoma from other neoplasms. For this reason, as in the present report, the definitive diagnosis was obtained through postmortem examination. (Ehrhart and Withrow, 2012).
Because it is an oncological condition, chemotherapy is the primary treatment option for feline lymphomas, potentially increasing survival (Chaves, 2024). This study also describes complete remission in up to 75.4% of cases when oncological therapy is administered, with intravenous vincristine (0.75 mg/m²) given for four weeks, oral cyclophosphamide (300 mg/m²) administered in the first and fourth weeks, and oral prednisolone (50 mg/m²) administered daily. In the present case, no oncological therapy was administered, and the patient's clinical condition unfortunately ultimately resulted in death.
CONCLUSIONS
This report highlights the importance of complementary imaging tests in supporting the neurological diagnosis and localization of lymphomas in felines. Another relevant point is the development of lymphomas in cats that do not carry the feline leukemia virus (FeLV). Although most lymphomas occur in FeLV-positive cats, their occurrence should also be investigated in FeLV-negative individuals, especially considering that spinal lymphoma is the most common spinal cord neoplasm in cats. Histopathological examination, in turn, has proven to be extremely important for the definitive diagnosis of lymphoma.
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The research data are available upon request.
Source: Vet Tomoclinica - Veterinary clinic specializing in diagnostic imaging.
