Spontaneous seminoma in medaka (<i>Oryzias latipes</i>)

Abstract

Although spontaneous development of seminoma is rare in medaka, we encountered spontaneous testicular tumors located within the abdominal cavity in two adult medakas. The growth patterns of the tumors were a combination of solid and cord arrangements in one of the two cases (Case I) and lobular in the other case (Case II). The tumor cells resembled the cells at different stages of spermatogenesis, and a small number of oocyte-like cells were also scattered within the tumor. The tumor with solid and cord patterns showed loss of normal testicular architecture, and the tumor cells had partly invaded the dorsal muscular tissue and metastasized to the liver, kidney, and eye. The tumor with a lobular pattern did not exhibit local invasion or metastasis. The tumors were diagnosed as seminomas based on their histopathological characteristics, and the tumor in Case I was observed to be more malignant than that in Case II.

Gonadal neoplasia in Chinese gold barbs (Barbodes semifasciolatus) from a home aquarium

“…In contrast, seminomas in mammals tend to exhibit dense proliferations of spermatogonia-like cells. Similar to this report, a malignant seminoma from medaka exhibited a solid to cord pattern (Kuroda et al, 2022).…”

“…Similarly, seminoma metastasis is rare in fish with only two reports in medaka (Kuroda et al, 2022;Tokarz & Wolf, 2022). A common finding with malignant seminomas among the current and previous reports is the exceptional size of the neoplasm relative to the size of the fish, suggesting that intravascular invasion and metastasis occur relatively late in disease progression (Kuroda et al, 2022;. This suggests that early detection and surgical intervention may prevent local extension into adjacent viscera and dissemination systemically (Vergneau-…”

“…When detected grossly, seminomas in fish often occur as expansile to infiltrative, well delineated, pink to off white, semi‐firm coelomic masses which cause coelomic distension and displace coelomic viscera. Locally extensive invasion into adjacent tissues is infrequently reported (Kuroda et al., 2022; Ott Knüsel et al., 2016). Additionally, case 1 showed intravascular invasion with various stages of developing spermatozoa in circulation, which is rare with seminomas in fish (Masahito, Ishikawa, & Takayama, 1984).…”

“…Additionally, case 1 showed intravascular invasion with various stages of developing spermatozoa in circulation, which is rare with seminomas in fish (Masahito, Ishikawa, & Takayama, 1984). Similarly, seminoma metastasis is rare in fish with only two reports in medaka (Kuroda et al., 2022; Tokarz & Wolf, 2022). A common finding with malignant seminomas among the current and previous reports is the exceptional size of the neoplasm relative to the size of the fish, suggesting that intravascular invasion and metastasis occur relatively late in disease progression (Kuroda et al., 2022; Masahito, Ishikawa, & Takayama, 1984).…”

“…When detected grossly, seminomas in fish often occur as expansile to infiltrative, well delineated, pink to off white, semi-firm coelomic masses which cause coelomic distension and displace coelomic viscera. Locally extensive invasion into adjacent tissues is infrequently reported (Kuroda et al, 2022;Ott Knüsel et al, 2016).…”