Stains & molecular markers
PLAP


Topic Completed: 21 January 2020

Revised: 21 February 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: PLAP [title]

João Lobo, M.D.
Rui Henrique, M.D., Ph.D.
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Cite this page: Lobo J, Henrique R. PLAP. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsplap.html. Accessed February 21st, 2020.
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
Terminology
Clinical features
Interpretation
  • 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.

Seminoma

PLAP staining in seminoma



Contributed by João Lobo, M.D.

Seminoma

GCNIS


GCNIS

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 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.

Reference: PLAP

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