S100P (placental S100) is a member of the S100 family.  It has been identified in human placenta and is expressed in a multitude of cancer types including: bladder, breast, esophagus, colon, lung, pancreatic, ovarian, hepatocellular (HCC), cholangiocarcinoma, and prostate (Yuan et al.).  Interesting, Mohanty, et al. found S100P to be a relatively sensitive and specific marker for urothelial carcinoma in the differential of urothelial carcinoma vs. poorly differentiated prostate adenocarcinoma of the bladder neck (88% sensitive, 100% specific, N=16).

 

Practically, S100P may have some useful benefit in a limited differential setting, but given its general lack of specificity would probably not be significantly helpful in the setting of a large differential diagnosis.

 

Yuan, et al. did find S100P expression to be an independent poor prognostic indicator in HCC with early tumor recurrence or high tumor stage.

 

Yuan, R.-H., Chang, K.-T., Chen, Y.-L., Hsu, H.-C., Lee, P.-H., Lai, P.-L., & Jeng, Y.-M. (2013). S100P expression is a novel prognostic factor in hepatocellular carcinoma and predicts survival in patients with high tumor stage or early recurrent tumors. PloS One, 8(6), e65501. doi:10.1371/journal.pone.0065501

 

Mohanty SK, Smith SC, Chang E, et al. Evaluation of contemporary prostate and urothelial lineage biomarkers in a consecutive cohort of poorly differentiated bladder neck carcinomas. Am J Clin Pathol. 2014;142(2):173–183. doi:10.1309/AJCPK1OV6IMNPFGL.