Reserve cell

Epithelial cell types of the uterine cervix. Reserve cells (right side of image) occur beneath the columnar epithelium and can proliferate during squamous metaplasia.
Histology of the cervical transformation zone showing squamous metaplasia. Reserve cells (R) proliferate beneath the columnar epithelium (C) during the development of immature squamous metaplasia.

Reserve cells are small, relatively undifferentiated epithelial cells located beneath the columnar epithelium of the uterine cervix, particularly in and around the transformation zone. They can proliferate and differentiate into squamous epithelium and are an important cellular component of cervical squamous metaplasia.

Histology and function

Histologically, reserve cells are small round or cuboidal cells with scant cytoplasm and relatively dark nuclei. They occur immediately beneath endocervical columnar cells and may be present singly, in linear arrays, or as larger proliferations termed reserve cell hyperplasia.

During squamous metaplasia, reserve cells proliferate beneath the columnar epithelium and progressively differentiate into immature and subsequently mature stratified squamous epithelium. Reserve cells and related immature metaplastic cells typically express the basal or squamous-associated markers p63, cytokeratin 5 (K5), and frequently cytokeratin 17 (K17). A 2025 study characterized cervical reserve cells as consistently K5/p63-positive, often K17-positive, and variably positive for the simple epithelial keratins K7 and K8.

Clinical significance

Reserve cells are of interest in cervical pathology because immature squamous metaplasia can resemble a squamous intraepithelial lesion. CK17 and p63 expression has been used to demonstrate reserve-cell and metaplastic differentiation.

Reserve cells and immature metaplastic epithelium have also been investigated as potential target cell populations for infection by high-risk human papillomavirus (HPV). HPV-associated high-grade squamous intraepithelial lesions frequently arise in the cervical transformation zone, including regions containing proliferating reserve cells and immature squamous metaplasia.

See also

References

  1. 1 2 3 4 Aiyenuro, Ademola A.; Griffin, Heather; Schichl, Konstanze; Omar, Tanvier; Ordi, Jaume; Kelly, Helen; Walker, Caroline; del Pino, Marta; Desai, Kanan; de Sanjosé, Silvia; Schiffman, Mark; Doorbar, John (2025). "Role of Reserve Cells in Metaplasia and the Development of Human Papillomavirus-Associated High-Grade Squamous Intraepithelial Lesions at the Cervical Transformation Zone". Laboratory Investigation. 105 (7) 104166. doi:10.1016/j.labinv.2025.104166. hdl:2445/227378. PMID 40204232.
  2. 1 2 Prendiville, Walter; Sankaranarayanan, Rengaswamy (2017). "Anatomy of the uterine cervix and the transformation zone". Colposcopy and Treatment of Cervical Precancer. IARC Technical Report. Lyon: International Agency for Research on Cancer.
  3. ↑ Regauer, Sigrid; Reich, Olaf (2007). "CK17 and p16 expression patterns distinguish (atypical) immature squamous metaplasia from high-grade cervical intraepithelial neoplasia (CIN III)". Histopathology. 50 (5): 629–635. doi:10.1111/j.1365-2559.2007.02652.x. PMC 1890920. PMID 17394499.