Nephroblastomas are uncommon embryonal tumors in dogs. We report herein a blastema-predominant nephroblastoma with gingival metastasis in an 8-y-old Miniature Pinscher dog. Histologically, the mass was composed mainly of blastemal elements with minor epithelial and mesenchymal differentiation. Metastatic masses in the gingiva had histologic and immunohistochemical features similar to those of the primary renal nephroblastoma. Neoplastic cells were extensively positive for both vimentin and PAX8, and scattered positive for cytokeratin. Using the clinical staging of human Wilms tumor, we staged our case as stage IV with <4 mo of survival time. We summarized previous studies of canine renal and spinal nephroblastomas, and analyzed the correlations among clinical staging, histologic classification, and mean survival time of dogs with renal nephroblastomas. Clinical staging was significantly correlated with survival time, as shown in humans. In dogs, however, additional factors can potentially influence the outcome of treatment and disease development.

Ovarian cancer is the most common cause of gynecologic cancer death. Both morphologically and immunohistochemically, metastatic mucinous tumors are the best mimickers of mucinous ovarian tumors; its pathogenesis still remains a mystery. PAX2 and PAX8 immunohisyochemistries are useful for differentiating numerous primary tumour types from metastatic ones. There are few studies in literature about PAX expressions in mucinous and seromucinous tumors. None of these are takes into account the histologic type (whether it is seromucinous or mucinous) or the metastatic origin. With this purpose hematoxylin and eosine slides of ovarian mucinous and seromucinous tumors were re-evaluated and one block was chosen for each case. The study included 76 ovarian mucinous and seromucinous tumors of the ovary reported in Hacettepe University department of pathology between 2000 and 2013. Tissue microarray (TMA) was designed from the chosen blocks, PAX2, PAX8, CDX2 immunostains was preformed to the TMA slides. As a result, most of the metastatic cases were negative for PAX2 (91.2 %) and PAX8 (86.3 %), many were diffusely and strongly positive for CDX2 (68.2 %). Seromucinous tumors were devoid of CDX2 expression; but all cases (except one) displayed strong and diffuse positivity with PAX8. In other words differing from mucinous tumors, seromucinous tumors show strong PAX8 positivity-similar to serous tumors. This study shows that PAX8 and CDX2 could be useful in differentiating primary mucinous from metastatic tumor. Furthermore unlike the homogeneity in seromucinous tumors for PAX8 and CDX2 mucinous tumors shows heterogeneity with different expression patterns.