Histopathological Features of Myxoid Pleomorphic Liposarcoma in an African Pygmy Hedgehog (Atelerix Albiventris)

SIMPLE SUMMARY: Liposarcoma is a malignant tumor that is derived from fat tissue. Liposarcoma is one of the most common malignant tumors in humans and animals. Liposarcomas are classified into six groups according to the WHO: dedifferentiated liposarcoma, myxoid liposarcoma, pleomorphic liposarcoma, liposarcoma not otherwise specified, atypical spindle cell/pleomorphic lipomatous and myxoid pleomorphic liposarcoma. Each subtype shows distinct pathological features, responses to chemotherapy and/or radiotherapy, and clinical outcomes. In this case, a myxoid pleomorphic liposarcoma was observed in a 5-year-old male African pygmy hedgehog. Myxoid pleomorphic liposarcoma is characterized by pathological features of both pleomorphic liposarcoma and myxoid liposarcoma. The tumor consisted of ~60% of the myxoid substance area and ~30% of pleomorphic neoplastic cells. The tumor presented similar clinical outcomes, including metastasis and prognosis, to myxoid liposarcoma rather than pleomorphic liposarcoma. This suggests that analyzing the proportion of pleomorphic area and myxoid area in myxoid liposarcoma could provide important information for predicting clinical outcomes. ABSTRACT: Myxoid pleomorphic liposarcoma is characterized by pathological features of both pleomorphic liposarcoma and myxoid liposarcoma, as the name suggests. In this case, a myxoid pleomorphic liposarcoma was observed in a 5-year-old male African pygmy hedgehog. It consisted of ~60% of the myxoid substance area with proliferating round cells and ~30% of pleomorphic neoplastic cells. The subject presented with extrapulmonary metastasis, but a good prognosis during 6 months of follow-up, which is similar to the characteristics of myxoid liposarcoma. The histopathological features of myxoid pleomorphic liposarcoma may reflect the features of either myxoid liposarcoma or pleomorphic liposarcoma depending on the proportion of each histopathological feature. The proportion of the pleomorphic area and the myxoid area may offer information on the prognosis and metastasis of myxoid pleomorphic liposarcoma, which will be helpful for setting up a treatment plan. Thus, analyzing the proportion of pleomorphic area and myxoid area could be suggested as one of the ways to predict clinical outcomes. In addition to the fact that this is the first case of a myxoid pleomorphic liposarcoma in hedgehogs, this case is meaningful, considering the unique histopathological characteristics and rare incidence of myxoid pleomorphic liposarcoma that could be important in humans as well.