P57kip2

Synonyms: CDKN1C, Cyclin-dependent kinase inhibitor 1C

by Jan Klos

Background

P57KIP2 is a protein encoded on chromosome 11p15.5 by CDKN1C gene. It is one of the cyclin dependent kinase (CDK) inhibitors. It is acting as cell cycle inhibitor. Loss of expression is expected to facilitate cell proliferation. It is one of paternally imprinted, but maternally expressed genes in humans. Mutations of CDKN1C are implicated in sporadic cancers and Beckwith-Wiedemann syndrome
In cases of hydropic degeneration of placenta and villi the trophoblastic cells are usually diploid (contain maternal and paternal genes). In partial mola trophoblastic cells are usually triploid and contain both maternal and paternal genes – persistent trophoblastic disease develops in 0,5- 5% of cases. In complete mola the cells are usually diploid and contain only paternal genes – persistent trophoblastic disease develops in 10-30% of cases.

Staining in normal tissues

Many human cells, in aborted material nuclei of decidual cells are positive and may be serve as positive controls. Cells of syncytiotrophoblast are negative.

Staining in tumors

Expressed in cell nuclei in many human tumors. Complete mola shows negative staining of nuclei in cytotrophoblast cells and stromal cells in chorion villi.

Staining pattern

Nuclear (some variation in intensity of nuclear staining may be seen).

Application

  • Differential diagnosis between complete and partial mola. In normal and hydropic abortus as well as partial mola – all types of trophoblastic cells are positive. In cases of complete mola cytotrophoblast and stromal cells in villi are not stained (negative staining). Concordance of this staining pattern with ploidy is 95%). Intervillous cytotrophoblast cells (intermediate trophoblast) are positive in complete mola up till 30% of cases. Syncytiotrophoblast is always negative.

Selected references

  1. Fukunaga M1. Immunohistochemical characterization of p57Kip2 expression in tetraploid hydropic placentas. Arch Pathol Lab Med. 2004 Aug;128(8):897-900.
  2. Fukunaga M1. Immunohistochemical characterization of p57(KIP2) expression in early hydatidiform moles. Hum Pathol. 2002 Dec;33(12):1188-92.
  3. https://en.wikipedia.org/wiki/Cyclin-dependent_kinase_inhibitor_1C