Confronting cisternae in canine testicular seminoma: special reference to appearance rate

A number of confronting cisternae (CC) were found in canine testicular seminomas (SEM). The CC consisted of two or three closely attached cisternae separated by an electron-dense layer, but occasionally four or more cisternae were stacked in a similar fashion. They showed a short, straight, and direct continuity with the rER or the nuclear envelope. They were found in SEM cells of both interphase and mitotic stages. We statistically examined 18 cases of canine SEM concerning the CC appearance rate in interphase cells (CCARI) and in mitotic cells (CCARM), and the tumor mitotic index (TMI). The SEM were classified into three groups (intratubular SEM without invasion, intratubular SEM with invasion, and diffuse type SEM) using Nielsen and Lein's classification (1974). The CCARI and TMI of the diffuse type SEM were significantly higher than those of the intratubular SEM with invasion, and those of the latter group were significantly higher than those of the intratubular SEM without invasion. On the other hand, the CCARM were similar between these three groups, and this parameter showed a non-significant correlation with the TMI. The present study suggests that the increase in the number of CC in interphase canine SEM cells might be correlated with the tumor progression.