Spontaneous Malignant T-cell Lymphoma in a Young Adult Crl:CD (SD) Rat

Abstract

We investigated a case of spontaneous malignant T-cell lymphoma observed in a 19-week-old male Crl:CD (SD) rat. The rat showed paralysis beginning 1 week before euthanasia. Hematological examination revealed marked lymphocytosis without distinct atypia. Macroscopically, hepatosplenomegaly and partial atrophy of the thoracic spinal cord were observed. Microscopically, neoplastic cells infiltrated into the liver, splenic red pulp, bone marrow and epidural space of the thoracic spinal cord, while no neoplastic cells were observed in the thymus and lymph nodes. Moreover, the spinal cord showed focal degeneration due to compression by marked infiltration of neoplastic cells in the subdural space. The neoplastic cells were generally small-sized round cells that had a round nucleus with/without a single nucleolus and scanty cytoplasm. Immunohistochemically, the neoplastic cells were positive for CD3 and CD8 and negative for CD79α. Judging from these results, the present tumor in this young adult rat was diagnosed as malignant T-cell lymphoma.

Differences in Types and Incidence of Neoplasms in Wistar Han and Sprague-Dawley Rats

“…In young adult rats (studies up to 26 weeks), the data on tumor incidences are limited. However, there are several case reports or organ-related summaries published (e.g., Chang et al 2008; Crabbs et al 2013; Matsushima et al 2010; Reindel et al 1996; Shiraki et al 2012; Tsunenari, Yamate, and Sakuma 1997), and summary data are available in the literature (e.g., Ikezaki, Takagi, and Tamura 2011; Lanzoni et al 2007; Son et al 2010). Tumors may be encountered in animals as young as 9 weeks.…”

“…Neoplasms are rare in young adult animals but in toxicity studies they may cause discussions on possible early inductions. Not many data have been published, but most are available on SD rats, for example, splenic hemangiosarcomas in a 9-week-old SD rat (Shiraki et al 2012), malignant lymphoma in a 19-week-old Crl: CD(SD) rat (Matsushima et al 2010), rhabdomyosarcoma in an 8-week-old SD rat (Chang et al 2008), carcinoma of the parotid gland in a 6-week-old SD rat (Tsunenari, Yamate, and Sakuma 1997), or malignant Sertoli cell tumor in the ovary of a 19-week-old female SD rat (Kinoshita et al 2016). A survey on the occurrence of amphophilic-vacuolar phenotypic variant in young SD rats was provided by Crabbs et al (2013).…”

Absence of reproductive and developmental toxicity in rats following exposure to a 20-kHz or 60-kHz magnetic field

“…Crl:CD(SD) rats occasionally develop malignant lymphoma late in life (Charles River Laboratories, 2001), although a rare case of lymphoma at 19 weeks of age was reported (Matsushima et al, 2010). Given that our independent 14-and 90-day toxicity studies with the same rat strain at the same MF exposures did not show any incidence of lymphoma (unpublished data), this isolated incident was considered to be spontaneous and statistically not related to MF exposure.…”

COMPARISON BETWEEN THORACIC RADIOGRAPHIC FINDINGS AND POSTMORTEM DIAGNOSIS OF THORACIC DISEASES IN DYSPNEIC COMPANION RATS (RATTUS NORVEGICUS)

“…Thymic lymphoma has also been reported, and all lymphopoietic tissues may be affected . Lymphomas may be characterized via immunohistochemistry as previously described in rats, and may be staged via bone marrow biopsy, similar to other species. In a clinical setting, ultrasound‐guided fine‐needle aspirations of thoracic masses may allow antemortem diagnosis of lymphomas in rats.…”

“…It was surprising that five patients from this database were diagnosed with lymphoma as spontaneous visceral lymphomas are considered uncommon in most rats strains, with the exception of Fisher 344 rats and inbred Sprague/Dawley/Cub rats . In Wistar rats, thymomas account for the majority of hematolymphopoietic tumors and are reported to be more common in females than in males .…”