Cutaneous lesions in a chipmunk (Eutamias sibiricus)

¹Antonio Meléndez-Lazo DVM MSc PhD DipECVCP MRCVS

²Laura Vilalta Soler DVM DipECZM (Small mammals)

¹LABOKLIN Labor für Klinische Diagnostik, Bad Kissingen (Germany)

²Universidad Católica de Valencia, Valencia (Spain)

SIGNALMENT AND HISTORY

A 9-year-old, intact male, (Eutamis sibiricus), weighing 77g presented after a 1-month history of cutaneous lesions. Initially, the lesions were localised on the right forelimb, but had recently spread into the cervical area. The animal was licking and scratching the area incessantly. Clinical examination revealed no abnormal findings, except for skin lesions. Dermatological examination revealed generalised erythema, multiple alopecic areas and an erosive-ulcerative lesion extending from the cervical to the pectoral region. Additionally, numerous yellow-brown crusts were present around this lesion (Fig.1).

PHYSICAL EXAMINATION

Clinical examination revealed no abnormal findings, except for skin lesions and increased size of lymph nodes. Dermatological examination revealed generalised erythema, multiple alopecic areas and an erosive-ulcerative lesion extending from the cervical to the pectoral region. Additionally, numerous yellow-brown crusts were present around this lesion (Fig.1).

INVESTIGATION

Hematology and biochemistry

Hematological examination revealed severe anemia, leukopenia and thrombocytopenia (pancytopenia). Serum biochemistry analysis was unremarkable.

Dermatological tests

-          Imprint cytology of cutaneous lesions: neutrophilic inflammation with bacterial infection

-          Trichoscopy: normal hair shaft with trauma-associated damage

-          Wood’s ultraviolet lamp examination: negative for fungi.

Cytology

Fine needle aspiration (FNA) cytology of the axillary lymph node was performed (Figure 2).

Other

-          Imaging: plain radiographs revealed unspecific age-related changes and increased lymph nodes’ size.

-          Fungal culture: negative

What is your interpretation of the cytology?

A predominant population of large lymphocytes (cross section over three times the diameter of a red blood cell) was present. Small lymphocytes were seen in lower numbers. Lymphocytes showed increased amount of cytoplasm and, frequently, a clear perinuclear area. Nuclei were round to oval, occasionally indented, eccentrically placed, with finely stippled to clumped chromatin pattern and 1 to various visible nucleoli.

These findings were consistent with a lymphoma.

What is the likely cause for the observed hematologic changes?

Bone marrow infiltration by lymphoid neoplastic cells is likely. However, bone marrow examination is recommended to better asses the cause for the pancytopenia.

Histological examination revealed a diffuse infiltration of round neoplastic cells affecting the epidermis, the superficial and mid dermis, and adnexal structures (Figure 3A) with formation of Pautrier’s microaggregations and demonstrating its epitheliotropic behaviour. On immunohistochemical examination the neoplastic lymphocytes were strongly positive for the T-cell marker CD3 (Figure 3B) but were negative for the B-cell marker CD20. Based on these finding a cutaneous epitheliotropic T-cell lymphoma (CETL), mycosis fungoides (MF) subtype, was diagnosed.

DIAGNOSIS: Cutaneous epitheliotropic T-cell lymphoma

TREATMENT AND FOLLOW-UP

Chemotherapy protocol was refused by the owner, and consequently prednisolone (0.5mg/kg orally BID) and doxycycline (5mg/kg orally SID) were initiated.

At 6 weeks recheck general health status had worsened, and the disease had progressed. Given the lack of response, poor prognosis, and poor quality of life the chipmunk was euthanatized. Necropsy was not performed to the owner’s request.

SUMMARY

Cutaneous lymphoma is an uncommon malignant cutaneous neoplasm. Histologically, it can be divided into nonepitheliotropic and epitheliotropic forms. Epitheliotropic cutaneous lymphomas are predominantly of T-lymphocyte origin, showing a specific tropism for the epidermis and adnexal structures. Cutaneous epitheliotropic T-cell lymphoma (CETL) has been reported in a variety of mammalian species, including dogs, cats, horses, cattle, marsupials, hedgehogs, ferrets, rabbits, and rodents (guinea pigs, hamster and gerbils). Generally, it occurs in old animals and has no gender predilection. In the majority of species, the clinical presentation of CETL is highly variable and the disease can mimic many dermatoses. Prognosis is generally poor. In this case, the neoplastic lymphoid population found in the lymph nose was likely the result of spreading from the cutaneous lymphoma.

Which other test would you carry out for a definitive diagnosis of the cutaneous lesions?

Biopsy and histological +/- immunohistochemical examination of the cutaneous lesions.

Three 4-mm punch skin biopsies were taken from the trunk, the right forelimb and the abdomen. The biopsies were routinely processed for histological (hematoxylin & eosin) and inmunohistological (CD3/CD20) examination.