# Ectopic Pregnancy and T-Cell Lymphoma in a Eurasian Red Squirrel (Sciurus vulgaris): Possible Comorbidity and a Comparative Pathology Perspective

## TL;DR

A Eurasian red squirrel had both an ectopic pregnancy and T-cell lymphoma, suggesting a possible link between these conditions in wildlife.

## Contribution

First reported case of concomitant ectopic pregnancy and lymphoma in a Eurasian red squirrel.

## Key findings

- A Eurasian red squirrel had a full-term ectopic pregnancy and T-cell lymphoma.
- The lymphoma infiltrated multiple organs, including the ovary, possibly contributing to the ectopic pregnancy.
- This case may represent the first known instance of these two conditions occurring together in any species.

## Abstract

Sciurus vulgaris, commonly known as the Eurasian red squirrel, is a wild rodent species widely distributed throughout Europe and currently classified as “least concern” by the International Union for Conservation of Nature (IUCN). Despite its conservation status, several threats, such as infectious diseases, habitat fragmentation and the introduction of the alien invasive species grey squirrel (Sciurus carolinensis), could affect S. vulgaris populations. Ectopic pregnancy is a condition consisting of a pregnancy developing outside the uterus. Tumors affecting the reproductive tract are known to predispose to this condition. In this paper, we describe for the first time a case of lymphoma leading to an ectopic pregnancy in a Eurasian red squirrel. A deeper knowledge of the pathology of this species is important for estimating the impact of diseases on the S. vulgaris population. Moreover, wildlife can be a sentinel for pathologies that have environmental causes and that could affect other animals and humans that share the same environment. Thus, deeper knowledge of wildlife cancer incidence and the environmental and individual causes of cancer development is relevant from a comparative pathology perspective.

Ectopic pregnancy (EP) is a life-threatening disease that affects humans and other mammals. Tumors causing ruptures of the reproductive tract have been identified as possible predisposing factors in human and veterinary medicine. We here describe a case of concomitant ectopic pregnancy and lymphoma in a Eurasian red squirrel found deceased in Italy and submitted to the public health laboratory Istituto Zooprofilattico Sperimentale del Lazio e della Toscana (IZSLT) for post-mortem examination. A full-term partially mummified ectopic fetus in the abdomen and a large fibrinonecrotic tubal scar adjacent to the right ovary were observed at necropsy. The tubal scar is likely the point of tubal rupture through which the fetus displaced. Histology revealed the presence of neoplastic cells referable to lymphoma infiltrating the ovary, spleen, small intestine, heart and peripancreatic adipose tissue. The lymphoma was further characterized as T-cell-type using immunohistochemistry. We suggest that the lymphoma, by involving the ovary, played a pathogenetic role in the development of a secondary EP by altering the genital tract at the structural and hormonal levels. To the best of our knowledge, this is the first report of concomitant ovarian lymphoma and EP in animals and humans in the literature.