Pathology Outlines

Stains
Ki67 / MIB1

Author: Nat Pernick, M.D. (see Authors page)

Revised: 10 November 2015, last major update October 2012

Copyright: (c) 2002-2015, PathologyOutlines.com, Inc.

PubMed Search: MIBI [title]

Table of Contents

Cite this page: Ki67. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/stainski67.html. Accessed July 12th, 2017.

Definition / general

A marker of cell proliferation first described in 1983 (Int J Cancer 1983;31:13)
Name derived from Kiel, Germany (city of origin) and the clone number in the 96 well plate (Wikipedia)
Labile, non-histone nuclear protein expressed in G1, S, G2 and M phases of cell cycle, then rapidly catabolized at end of M phase and not detectable in G0 and early G1 cells (J Cell Physiol 2000;182:311)
MIB1 is the IgG1 antibody against Ki67 for formalin-fixed, paraffin embedded tissue

Uses by pathologists

Nuclear stain; cytoplasmic staining is not important
Determine growth fraction of tumor:
- Distinguish benign/non-neoplastic and malignant/neoplastic lesions:
  - Anus/cervix: HSIL (Ki67+) versus atrophy or normal (Ki67-, Am J Surg Pathol 2010;34:1449)
  - Colonic polyp with cautery artifact: distinguish adenoma (Ki67+) from nonadenomatous polyp (Ki67-, Arch Pathol Lab Med 2007;131:1089)
  - Lymph node, sentinel node biopsy: distinguish melanoma (Ki67+) from nevus cells (Ki67-, Am J Surg Pathol 2002;26:1351)
  - Uterus: clear cell carcinoma (Ki67+) versus Arias-Stella reaction (Ki67-)
- Classify lesions:
  - Placenta: distinguish hyperplasia of intermediate trophoblast (Ki67+) from exaggerated placental site (Ki67-)
- Tumor classification:
  - Adrenocortical tumors: distinguish benign and malignant (Am J Surg Pathol 2002;26:1612)
  - Breast phyllodes tumors: distinguish benign, borderline, malignant (low grade / high grade, Mod Pathol 2001;14:185)
- Poor prognostic factor (high levels):
  - Examples: bladder papillary urothelial neoplasm of low malignant potential (Cancer 2002;95:784), chordoma (Arch Pathol Lab Med 2010;134:1170)
  - Part of staging for appendiceal carcinoid and grading for GI neuroendocrine tumors (Hum Pathol 2012;43:489)

Microscopic (histologic) images

Images hosted on PathOut server:

Skin, symplastic glomus tumor, toe

Small bowel, malignant GIST

Tonsil, normal, c/o Leica Microsystems

Urethra, clear cell adenocarcinoma

Lymph node, normal

Lymph node, Burkitt lymphoma

Cervix, adenocarcinoma in situ, endocervix

Images hosted on Other servers:

Breast, hemangioma vs high grade angiosarcoma

Breast, invasive carcinoma, basal-like subtype with high Ki67 index

LUMA tumor

Colon, adenomatous vs nonadenomatous polyps

Kidney, malignant solitary fibrous tumor

Lymph node, diffuse large B cell lymphoma

Pancreas, islet cell tumors

Uterus (left to right), mid-proliferative endometrium, day 17 endometrium

Nature images:

Breast, invasive carcinoma

Skin, Spitz nevus

Skin, nevi vs melanoma

Lymph node, Burkitt lymphoma

Breast, phyllodes tumors

Positive staining - normal

Placenta, early (cytotrophoblast: 25-50%, intermediate villous trophoblast: >90%)

Positive staining - disease

High grade neoplasms, including Burkitt lymphoma, carcinoma in situ, invasive carcinomas (many), malignant phyllodes tumor (breast), sarcomas (many)
Conjunctival Spitz nevus and squamous papilloma are Ki67+

Negative staining

Most benign or reactive lesions; nevi