Sarcomatoid carcinoma of the prostate - A single institution experience with emphasis on molecular genetic findings.

Sarcomatoid carcinoma of the prostate (SCP) is a rare neoplasm known for its diagnostic difficulties and aggressive clinical course. Given the paucity of literature on its molecular landscape, we aimed to investigate a cohort of SCP, using a multi-modal approach. Our surgical pathology archive was queried for patients diagnosed with SCP (2006-2022), followed by re-review of archived slides. For each case, a panel of immunohistochemical stains (including programmed death-ligand 1 [PD-L1] clones SP142, SP263, and 22C3) was performed on a representative block. Fluorescence in situ hybridization (FISH) was used to evaluate chromosomes 10 (including PTEN) and 17 (including TP53). All cases were evaluated using a next-generation sequencing (NGS) panel. Eight patients were included. Three (37.5 %) had a prior history of acinar adenocarcinoma, while a concomitant adenocarcinoma was present in five patients (62.5 %). The median duration of follow-up was 20.5 months. Seven patients (87.5 %) presented with or developed systemic metastases during follow-up. At last follow-up, 6 patients (75 %) were dead of disease. Three of the 7 cases (42.9 %) assessed for PD-L1 expression showed some staining. The most common pathogenic alterations identified by NGS involved TP53 (n = 5), followed by APC, BRCA2, CHECK2, CTNNB1, and RB1 (n = 1, each). On FISH testing, copy number changes involving chromosome 10 and 17 were found in 80 % and 60 % of the cases, respectively. This study sheds light on the molecular landscape of SCP, which may be valuable to elucidate the prognostic and therapeutic implications for this uncommon disease.