Leopards (Panthera pardus) are large-sized wild felids and are widely distributed in Sub-Saharan Africa, Western and Central Asia, Southern Russia, and Southeast and East Asia; they are classified as vulnerable (A2cd, version 3.1) on the International Union for Conservation of Nature Red List of threatened species (22).

Cutaneous squamous cell carcinoma (SCC) is a common tumor accounting for 5.4% of all cutaneous tumors in dogs, 17.5% of all cutaneous tumors in cats, and 16.7% of all cutaneous tumors in captive Panthera species (4,13). Multiple types of cutaneous SCCs are aggressive and locally invasive and frequently metastasize to the regional lymph nodes, but rarely metastasize distantly (5). Exposure to sunlight, especially ultraviolet (UV) radiation, is the main cause of cutaneous SCC (1). SCC usually begins with actinic dermatitis (AD) lesions along with erythema, scales, crusts, and desquamation (7,17). AD is a pre-malignant lesion that can to invasive SCC with exposure to long-term actinic radiation (17). Plaque formation and ulceration usually indicate the development of SCC (14,17). Although SCC is a commonly diagnosed tumor in companion animals, only a few cases of SCC have been reported in wild felids including the Clouded leopard (Neofelis nebulosa), Snow leopard (Uncia uncia), Siberian tiger (Panthera tigris altaica), and African lion (Panthera leo) (3,8,12,16,18). There has been only one other reported case of SCC in a leopard, which was a case of pulmonary SCC (19).

This report describes a case of a leopard with cutaneous SCC of the tail that was diagnosed by histopathology.

A 14-year-old intact male leopard that was born in a zoo developed a focal alopecic lesion (5 × 6 cm) on the dorsal aspect of the distal one-third of the tail (Fig. 1A). The lesion was first treated with itraconazole (Ashicona, JSK) at 10 mg/kg PO once daily and ursodeoxycholic acid (Ursa; Daewoong) at 100 mg/body PO once daily for 28 days based on a presumptive diagnosis of mycotic infection. However, the lesion did not improve, and the leopard continued licking the lesion, which caused the epidermis to exfoliate and the wound to deepen (Fig. 1B). A fine-needle aspiration (FNA) biopsy was performed, but significant cells for cytology were not obtained. The leopard was in great distress; thus, it became too difficult to safely perform daily wound dressing and to maintain the tail bandages without anesthesia. Therefore, tail amputation was considered the best course of action to improve the management and prognosis (Fig. 1C). Before surgery, a complete blood cell count (CBC) and blood chemistry analysis were performed by Exigo H400 hematology analyzer (Boule Medical AB, Spånga, Sweden) and Vetscan VS2 Chemistry analyzer (Zoetis, New Jersey, USA). The test results were compared with the reference interval of the Leopard (Panthera pardus), Indian leopard (Panthera pardus fusca), and Amur leopard (Panthera pardus orientalis) (2,20,21). CBC results were no remarkable findings, and the blood chemistry results revealed an elevated blood urea nitrogen level, an elevated creatinine level, hypocalcemia, and hyperkalemia (Table 1). After the amputation, tramadol (Tridol, Yuhan) at 2 mg/kg PO once daily, amoxicillin/clavulanate (Zakutex, Theragen Etex) at 11 mg/kg PO once daily, and gabapentin (Neurontin, Pfizer) at 300 mg/body PO once daily were administered. A tissue sample was fixed in 10% neutral-buffered formalin and submitted for histopathological examination.

Table 1 . Hematology and blood chemistry test results of the leopard before operation.

Parameter	Value	Reference interval
		Leopard*	Indian leopard**	Amur leopard***
WBC (× 103/μL)	18.6	1.6-13.7	14.9-17.5	5.80-17.8
RBC (× 106/μL)	7.05	6.5-15.5	8.3-9.1	6.17-10.5
Hemoglobin (g/dL)	11.5	8.4-14	14.2-15.3	9.26-17.4
PCV (%)	34.7	32-42	47.0-50.0	30.7-51.8
MCV (fl)	49	29.2-54.1	56.2-61.1	40.2-57.7
MCH (pg)	16.4	9.8-19.1	17.4-18.7	13.2-17.8
MCHC (g/dL)	33.2	21.5-98.4	30.1-31.3	25.0-36.0
Platelets (× 103/μL)	165	140-250	-	258-603
Total protein (g/dL)	8.1	2.5-8.5	6.7-7.3	6.06-8.46
Albumin (g/dL)	4	2.8-6.4	3.7-4.1	3.22-4.40
Globulin (g/dL)	4.1	-	2.8-3.3	2.30-4.73
ALP (IU/L)	10	12.7-88.5	-	0-43.0
ALT (IU/L)	63	18-92	-	28.8-109
Glucose (mg/dL)	170	80-135	50.4-66.9	-
Amylase (IU/L)	388	-	-	123-603
Total bilirubin (mg/dL)	0.2	0.4-1.6	-	-
BUN (mg/dL)	90	19-60	25.1-30.0	19.6-49.2
Creatinine (mg/dL)	5.3	0.24-2.35	1.4-1.7	1.01-3.02
Ca (mg/dL)	<4.0	-	9.2-10.6	7.96-11.8
P (mg/dL)	NM	-	5.1-5.9	4.05-12.8
Na (mmol/L)	161	-	-	141-161
K (mmol/L)	>12.0	-	-	3.36-4.58

WBC, white blood cells; RBC, red blood cells; PCV, packed cell volume; MCV, mean cell volume; MCH, mean cell hemoglobin; MCHC, mean cell hemoglobin concentration; ALP, alkaline phosphatase; ALT, alanine aminotransferase; BUN, blood urea nitrogen; NM, not measured..

*Shrivastav et al. 2015 (21)..

**Shanmugam et al. 2017 (20)..

***Bodgener et al. 2017 (2)..

Figure 1. Gross lesions on the tail of the leopard. (A) First presentation to the clinician. Focal alopecia lesion found on the dorsal aspect of distal one-third region on the tail. (B) Inflammation and ulceration secondary to self-licking behaviors. (C) After amputation. The size of the ulcerative lesion was 5 × 6 cm in diameter.

A complete histopathological examination revealed that the lesion was covered with diffuse epidermal hyperplasia. Multifocal neoplastic foci occupied the dermis of the mass and were focally covered with stratified squamous epithelium. These foci were composed of neoplastic islands with squamous differentiation and were widely distributed throughout the mass. The neoplastic islands were composed of multiple layers of prickle cells of squamous epithelium and central necrotic cellular debris, which are also called typical keratin pearls (Fig. 2A). These neoplastic prickle cells had typical intercellular bridges. Moderate desmoplasia and chronic inflammation were also observed surrounding the neoplastic foci. Individual cells had characteristics of anisocytosis, anisokaryosis, marked nucleoli, and mitotic figures (Fig. 2B, C). The neoplastic cells showed an invasive tendency to spread to the adjacent tissues such as lower connective tissues.

Figure 2. Photomicrograph of the histopathological features of the lesions. (A) Typical keratin pearls (asterisk). (H&E stain, ×200). (B) Anisokaryosis and marked nucleoli (arrow) (H&E stain, ×400). (C) Mitotic figures (circle) (H&E stain, ×400).

Following the amputation, the leopard’s appetite significantly decreased. Eighteen days after the amputation, the patient died. Prior to its death, diagnostic imaging examinations such as computed tomography (CT) were not performed to evaluate for metastasis according to the histopathology results. However, although a Postmortem CT scan was performed after the patient’s death, the scan was not evaluated for metastasis because no contrast media was administered.

This report describes a case of well-differentiated, cutaneous SCC on the tail of a leopard. The lesion first developed as focal alopecia followed by a secondary ulcerative lesion caused by self-trauma.

In feline species, cutaneous SCC is usually found on the head, including the pinna, eyelids, and nasal planum, and this tumor may appear as plaque-like lesions covered with erythema, ulcerations, or crusts (10,11,15). SCC is often misdiagnosed as one of several types of simple infectious skin diseases because initial lesions of SCC usually appear as ulcerations with or without bacterial infection, whereas other skin tumors commonly form a solid mass (23).

The cytological characteristics of SCC include high cellularity with round or angular morphologic epithelial cell clusters that have malignant features including marked nucleoli and moderate to marked anisocytosis and anisokaryosis. In addition, the color of the cytoplasm may be deep blue in appearance (9).

In this leopard's case, there were several problems during the diagnostic process. First, FNA biopsy failed to obtain a significant number of cells with one sampling. If more cells had been collected by FNA biopsy or if additional FNA biopsies had been performed, SCC might have been diagnosed prior to histopathology based on the cytological features of SCC. Second, SCC was not a top differential diagnosis due to the atypical location of the lesion on the tail since in domestic animals, such as dogs and cats, lesions are usually found on the head. Third, considering that this leopard was a large captive wild animal, considerable focus was placed on the presumptive diagnosis. A mycotic infection was suspected although fungal culture or an impression smear was not performed. Due to the self-trauma behavior, the lesion was presumed to be a lick granuloma with ulceration. Had these mistakes been avoided, amputation might have been performed earlier, or the leopard could have undergone chemotherapy or radiation therapy to possibly prevent death. In domestic cats, the median survival time of a patient with cutaneous SCC who receives radiation therapy is 224 days; however, no study has reported the median survival time of a patient with cutaneous SCC that remained untreated (6). Based on this reference, there is a possibility that the leopard could have survived longer if more proactive treatment had been implemented. Therefore, when the initial diagnosis and treatment of a suspected infectious disease fails, a differential diagnosis of a tumor based on repeated cytological or histopathological examination should be considered.

Performance of diagnostic tests and treatment of diseases in large wild animals are very challenging because they often require anesthesia. Nevertheless, if appropriate examinations are not performed, the disease may be misdiagnosed. Clinicians should be aware of the possibility that tumors may present as ulcerative lesions that fail to respond to treatment as infectious skin diseases. To the authors’ knowledge, the case of cutaneous SCC in a leopard described here is the first report case in this species.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (NRF-2016R1D1A1B03932312). The authors would like to thank Dr. Sun-A Kim for her helpful advice and comments.

The authors have no conflicting interests.