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Introduction: Tumor collision is the encounter of two tumors from two different topographical sites. Cases of metastatic lymph node collision are exceptional. We report the case of a metastatic lymph node collision of an urothelial carcinoma and a prostatic adenocarcinoma., Observation: A 61-year-old man was hospitalized for a right nephroureterectomy with peri-ureteral lymph node dissection. He was followed since 2004 for prostatic adenocarcinoma and treated with radical prostatectomy then radiation therapy 4 years later due to a new increase of PSA. In the follow-up, an urothelial carcinoma of the lower right ureter was discovered in 2014. Histological analysis of a peri-ureteral lymph node showed a double metastasis of urothelial and prostatic origin. The prostatic adenocarcinoma was composed of acinar and ductal subtypes. Immunohistochemical study including CK7, CK20, PSA, GATA3, P63 antibodies confirmed the distinct phenotype of the 2 tumors., Discussion: Metastatic collision of urothelial carcinoma and prostatic adenocarcinoma has been reported in 4 cases only. Our review of literature shows that prostatic adenocarcinoma always precedes the urothelial carcinoma. Immunohistochemical study, when carried out for distinguishing both tumors, should include CK7, CK20 and PSA. GATA3, androgen receptor and P63 could be added in a second time., (Copyright © 2015. Published by Elsevier Masson SAS.)

Basal cell carcinoma with matrical differentiation is a very rare variant of basal cell carcinoma. To our knowledge, less than 30 cases have been reported. This tumor is composed of basaloid lobules showing a differentiation toward the pilar matrix cells. Recently, it has been demonstrated that beta-catenin would interfer with physiopathogenesis of matrical tumors, in particular pilomatricomas, but also basal cell carcinomas with matrical differentiation. This is a new case, with immunohistochemical and molecular analysis of beta-catenin, in order to explain its histogenesis., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)