Tumors in pet hamsters in Korea: a retrospective study of 80 cases (2017–2023)

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Korean J Vet Res. 2025;65.e12

Publication date (electronic) : 2025 June 30

doi : https://doi.org/10.14405/kjvr.20250014

Dayoung Choi¹, Da-Ye Nam¹, Jae-Hoon Kim¹, Hannah Kim², Kyunghwa Hong³, Hyunwoo Joo⁴, Ji-Youl Jung^1,

¹College of Veterinary Medicine and Veterinary Medical Research Institute, Jeju National University, Jeju 63243, Korea

²Hana Animal Hospital, Seoul 02496, Korea

³Anyang Animal Medical Center, Anyang 14006, Korea

⁴Teun Teun Animal Hospital, Jeju 63231, Korea

^*Corresponding author: Ji-Youl Jung College of Veterinary Medicine, Jeju National University, 102 Jejudaehak-ro, Jeju 63243, Korea Tel: +82-64-754-3364 E-mail: jungjy1982@jejunu.ac.kr

Received 2025 March 14; Revised 2025 June 3; Accepted 2025 June 19.

Abstract

Introduction

Hamsters belong to the order Rodentia and are popular pets worldwide. The Syrian or golden hamster (Mesocricetus auratus) is the most common pet species, followed by dwarf hamsters, such as the Djungarian or Russian dwarf hamster (Phodopus sungorus) [1,2]. Despite the growing popularity of pet hamsters, scientific literature still focuses more on laboratory hamsters. Among the reports on tumors in pet hamsters, integumentary tumors are most frequently observed in Djungarian hamsters, whereas hematopoietic tumors predominate in golden hamsters [3,4]. However, the types of integumentary tumors vary across studies. Kondo et al. [3] reported that atypical fibromas and papillomas were the most common integumentary tumors, whereas Rother et al. [4] reported that papillomas, adenomas, and adenocarcinomas were more prevalent in Djungarian hamsters. This study aimed to investigate the affected organ systems and types of naturally occurring tumors in pet hamsters, with a specific focus on integumentary tumors, in South Korea.

Materials and Methods

Eighty biopsy specimens from pet hamsters, submitted to the Laboratory of Veterinary Pathology at Jeju National University between January 2017 and December 2023, were analyzed. Formalin-fixed tissue specimens were collected by veterinary practitioners from animal hospitals in Seoul, Gyeonggi-do, and Jeju, Korea.

Routine histological processing was performed: paraffin-embedded tissue blocks were sectioned at a thickness of 4 μm, followed by deparaffinization and rehydration using a graded series of alcohols. The sections were then stained with hematoxylin and eosin. In certain cases, additional sections were stained with special stains, including Masson’s trichrome, periodic acid-Schiff (PAS), and PAS with diastase (PAS-D), to aid in diagnosis.

Following histopathological diagnosis, information on species, sex, age, affected system, and anatomical lesion location was obtained from the histopathological reports and associated clinical medical records.

Tumors were categorized by organ system (integumentary, reproductive, hematopoietic, mammary gland, and skeletal) and further subdivided by pathological diagnosis. Given that the integumentary system accounted for the majority of cases (n = 54), additional analyses were conducted on integumentary tumors in Djungarian hamsters.

Results

A total of 80 cases were diagnosed in 70 Djungarian hamsters and 10 golden hamsters. Of the 70 Djungarian hamster specimens, 40 were from females, including one from a spayed female, and 30 were from males. Similarly, of the 10 golden hamster specimens, 9 were from females, and one was from a male.

The ages of both hamster species ranged from 5 to 30 months, with a median of 16.4 months. The median age of the Djungarian hamsters was 16.6 months (range, 5–30 months), while the median age of golden hamsters was 15 months (range, 5–21 months). Tumors were predominantly localized to the integumentary system, accounting for 57 cases (71.3%), followed by the reproductive system (13, 16.3%), hematopoietic system (6, 7.5%), mammary glands (3, 3.8%), and skeletal system (1, 1.3%) (Table 1).

Table 1.

Tumor distribution and frequency in Djungarian and golden hamsters

Tumor types in Djungarian hamsters

Seventy cases of tumors in Djungarian hamsters are summarized in Table 2. The integumentary system was the most commonly affected (54 cases, 77.1%), followed by the reproductive system (9 cases, 12.9%), mammary glands (3 cases, 4.3%), hematopoietic system (3 cases, 4.3%), and skeletal system (1 case, 1.4%).

Table 2.

Tumor cases in Djungarian hamsters: organ system, diagnosis, sex, and age

The most common integumentary tumor diagnosis in Djungarian hamsters was cutaneous atypical fibroma (15 cases, 27.8%) (Fig. 1A and B), followed by apocrine adenoma (9 cases, 16.7%) (Fig. 1C) and trichoepithelioma (5 cases, 9.3%). Among the 15 cases of cutaneous atypical fibroma, all cases occurred in male hamsters. In contrast, apocrine gland tumors were diagnosed in 18 cases (33.3% of integumentary tumors), and all cases occurred in female hamsters.

Fig. 1.

Histopathologic findings in the skin of hamsters. (A) Cutaneous atypical fibroma, Djungarian hamster. The neoplastic foci consist of variable numbers of spindle-shaped or polygonal cells with moderate amounts of collagenous extracellular matrix (hematoxylin and eosin staining [H&E], scale bar = 50 µm). (B) Cutaneous atypical fibroma. Djungarian hamster. Neoplastic cells exhibit blue staining with Masson’s trichrome, indicating collagen deposition (scale bar = 50 µm). (C) Apocrine adenoma. Djungarian hamster. Neoplastic columnar epithelial cells with abundant granular cytoplasm form acinar structures (H&E, scale bar = 50 µm; inset: PAS-D resistant granules observed in the epithelial cytoplasm). (D) Cutaneous lymphoma, golden hamster. Massive infiltration of pleomorphic lymphocytes into the dermis (H&E, scale bar = 20 µm).

The anatomical region most commonly affected by integumentary tumors was the abdomen (23 cases, 42.6%), followed by the thorax (19 cases, 35.2%), limbs (6 cases, 11.1%), and head (5 cases, 9.3%). Among the 15 cases of cutaneous atypical fibroma, 9 occurred in the thoracic region and 6 in the abdominal skin. Among the 18 cases of apocrine gland tumors, 8 occurred in the abdomen and 7 in the thoracic region (Table 3).

Table 3.

Anatomical distribution of integumentary tumors in Djungarian hamsters

Reproductive tumors occurred predominantly in female hamsters, with most originating from the uterus (adenoma/adenocarcinoma, leiomyoma/leiomyosarcoma) and vagina (vaginal squamous papilloma). Mammary gland tumors were identified in only 3 cases (4.3%), indicating a relatively low incidence.

Tumor type in golden hamsters

Tumors in golden hamsters are summarized in Table 4. Of the 10 cases, four were associated with the reproductive system, 3 with the hematopoietic system, and 3 with the integumentary system. All 3 tumors diagnosed in the hematopoietic system were lymphomas (Fig. 1D).

Table 4.

Tumor cases in golden hamsters: organ system, diagnosis, sex, and age

Discussion

We retrospectively collected 80 spontaneous tumors from pet hamsters in South Korea between 2017 and 2023. The integumentary system was the most commonly affected, followed by the reproductive, hematopoietic, mammary gland, and skeletal systems. The high prevalence of integumentary tumors in these animals is likely due to the ease with which owners can observe and palpate abnormalities on the skin, leading to earlier detection and more frequent submission for histopathological examination.

The total number of spontaneous tumors in Djungarian hamsters was greater than that in golden hamsters. Three studies have described tumors in pet hamsters from Japan, Germany, and Brazil [3–5]. Compared to golden hamsters, Djungarian hamsters exhibit a higher incidence of tumors, a finding consistent with previously reported data [4]. The underlying reason for this high incidence remains unclear [4]. A previous study suggested that differences in chromosome number between these 2 species could contribute to variations in tumor prevalence and frequency [3].

The spectrum of spontaneous tumors in Djungarian hamsters differs from those in golden hamsters [6]. Djungarian hamsters were primarily affected by integumentary tumors (atypical fibroma and papilloma), whereas golden hamsters were more commonly diagnosed with hematopoietic tumors (plasmacytomas and lymphoma) [3]. However, our findings differ from those of previous studies. In Djungarian hamsters, integumentary tumors were the most frequently observed, whereas in golden hamsters, reproductive tumors were the most common. However, this finding should be interpreted with caution due to the small sample size (n = 10). Moreover, the number of tumors originating from the reproductive system (n = 4) and hematopoietic system (n = 3) was relatively similar, and the slight difference may not be statistically or biologically meaningful. Additionally, hematopoietic tumors were also detected in Djungarian hamsters.

The average lifespan of hamsters is 18 to 24 months, and tumors are common in older individuals [3,7]. In our study, the median age of the hamsters was 16.4 months, which was lower than that reported in a comparable study on spontaneous tumors in pet hamsters (19.8 months) [3]. However, this age was higher than the mean age reported in another study (14 months) [5]. Tumors in laboratory hamsters younger than 12 months are rare [5]. However, in our study, 14 out of 80 cases (17.5%) involved hamsters younger than 12 months.

Some studies have reported a higher incidence of tumors in female hamsters than in males [3,5], and our study on golden and Djungarian hamsters is consistent with this finding. However, sex distribution varied by tumor type. In particular, mammary gland tumors and atypical fibromas were prominent, as noted in a previous study [3].

All mammary tumors were found exclusively in female Djungarian hamsters. The median age of Djungarian hamsters with mammary tumors was 7 months, which was lower than that for all other tumor types, consistent with the findings of Kondo et al. [3].

Mammary gland tumors are among the most frequently occurring tumors in dogs and cats, with various histological subtypes reported [8]. However, in this study, the incidence of mammary gland tumors was relatively low, showing a different pattern from that observed in dogs and cats [3,5]. In contrast, our study identified apocrine gland tumors as the second most common neoplasm in Djungarian hamsters, contrary to previous reports describing them as extremely rare [3].

Histologically, these tumors closely resemble mammary gland tumors, necessitating a careful differential diagnosis. Key histopathological features must be evaluated, including evidence of apocrine secretion and eosinophilic cytoplasm containing PAS-D resistant granules to confirm the diagnosis of apocrine gland tumors [9]. In this study, the distinction between these 2 tumor types was primarily based on the characteristic features of the glandular epithelium, particularly the presence of apical blebs in apocrine gland tumors and PAS-D resistant granules.

Atypical fibromas and fibrosarcomas are cutaneous tumors characterized by large ganglion cell-like cells supported by varying amounts of collagen fibers [10]. These cells are typically found in the dermis or subcutaneous adipose tissue of the abdominal and thoracic skin of Djungarian hamsters [10].

Atypical fibromas (fibrosarcomas) are predominantly reported in male Djungarian hamsters and are rarely observed in females, as these tumors are androgen-dependent [11]. In our study, all atypical fibromas were observed in male Djungarian hamsters; however, one case (atypical fibrosarcoma) was observed in a female hamster.

According to Baba et al., the thoracoabdominal area is the predilection site for atypical fibromas [10]. Our findings were consistent with this observation, as 15 cutaneous atypical fibromas were located in the thoracoabdominal area, while one malignant tumor was found in the limb.

Integumentary tumors were the most common in Djungarian hamsters, whereas reproductive system tumors predominated in golden hamsters. However, this pattern was observed only in pet hamsters. In laboratory hamsters, tumors affect multiple organs rather than being prevalent in specific organ systems [12].

The incidence of reproductive system tumors, particularly in female hamsters, was relatively high in this study. Ovariohysterectomy may be recommended for female hamsters to prevent reproductive diseases, including tumors [8]. Spontaneous tumors of the testes are rare but were observed in our study [4].

In conclusion, our study reinforces the patterns and predilections of spontaneous tumors in pet Djungarian and golden hamsters, particularly regarding tumor prevalence, type, and location. These findings align with prior research, which highlighted a high incidence of integumentary and reproductive system tumors in pet hamsters, along with significant sex- and age-related patterns. Although laboratory hamsters exhibit a broader distribution of tumor sites across various organ systems, pet hamsters appear to be more predisposed to specific tumors, particularly those affecting the integumentary system.

Future studies with larger sample sizes and comprehensive necropsies could further clarify the tumor profile in pet hamsters and refine preventive strategies. Additionally, due to the retrospective design and incomplete follow-up data in many cases, it was not possible to determine the survival periods following tumor diagnosis. Future prospective studies with monitoring are needed to clarify the relationship between tumor types and survival outcomes. Our findings have veterinary implications for both clinical management and preventive care, particularly in female hamsters, and underscore the importance of monitoring common tumor sites to improve the health and longevity of pet hamsters.

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