Stains & CD markers

Editor-in-Chief: Debra L. Zynger, M.D.
João Lobo, M.D.
Rui Henrique, M.D., Ph.D.

Last author update: 21 January 2020
Last staff update: 15 July 2022

Copyright: 2002-2023,, Inc.

PubMed Search: PLAP [title]

João Lobo, M.D.
Rui Henrique, M.D., Ph.D.
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Page views in 2023 to date: 851
Cite this page: Lobo J, Henrique R. PLAP. website. Accessed February 3rd, 2023.
Definition / general
  • Placental-like alkaline phosphatase, a marker of germ cell tumors, especially seminoma
  • Sensitive but not a specific marker
Essential features
  • Placental-like alkaline phosphatase, part of a family of alkaline phosphatases with 4 members
  • High levels in serum of seminoma patients (sensitive) but also detected in several normal and disease conditions (not specific)
  • Sensitive immunohistochemical marker for germ cell neoplasms (testicular, ovarian and extra gonadal) and germ cell neoplasia in situ (GCNIS) but not specific
  • Virtually always positive (strong and diffuse) in seminomas; useful for discriminating from spermatocytic tumor
Clinical features
  • Membranous and cytoplasmic staining are expected
Uses by pathologists
  • Supporting diagnosis of germ cell neoplasms, including the precursor lesion germ cell neoplasia in situ and overt germ cell tumors (testicular, ovarian and extra gonadal)
  • Mainly a marker of seminoma (also dysgerminoma and germinoma of the brain) - positive in up to 100% of seminomas, strong diffuse positivity; useful for distinguishing seminoma from spermatocytic tumor
  • Also frequent low intensity and focal expression in embryonal carcinoma and yolk sac tumor (in 85 - 97% of the cases)
  • Focal positivity in cytotrophoblast cells of choriocarcinomas and in immature teratoma elements may be seen (Urol Res 1990;18:87, Am J Surg Pathol 1987;11:21, Eur J Obstet Gynecol Reprod Biol 1998;81:123, J Neurosurg 1985;63:733)
Microscopic (histologic) images

Contributed by João Lobo, M.D. and Rui Henrique, M.D., Ph.D.


PLAP staining in seminoma




Yolk sac tumor

Embryonal carcinoma

Positive staining - normal
Positive staining - disease
Negative staining
Board review style question #1
    Which of the following sentences is true about the immunohistochemistry marker PLAP?

  1. It is specific for seminoma histology
  2. Staining is observed in germ cell tumors of the testis but not in ovarian ones
  3. Nuclear staining is expected
  4. Staining is evident across histologies, including in spermatocytic tumor
  5. It is useful for detecting germ cell neoplasia in situ
Board review style answer #1
E. PLAP is positive and useful for spotting germ cell neoplasia in situ. Despite being a sensitive marker, it is not specific for seminoma, being positive in several other tumors (both germ cell and nongerm cell malignancies) and normal tissues. Staining is membrane and cytoplasmic. It is useful for distinguishing seminoma from spermatocytic tumor, an important differential diagnosis, since spermatocytic tumor is negative.

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Reference: PLAP
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