• Cytokeratin expression in desmoplastic small round cell tumor of the abdomen (DSRCT).
  • Cytokeratin expression in desmoplastic small round cell tumor of the abdomen (DSRCT). Overlying mesothelium is also stained by keratin.
  • Cytokeratin AE1/3 staining in skin.
  • Cytokeratin AE1/3 staining in colonic mucosa.
  • Cytokeratin AE1/3 staining in lung.
  • Cytokeratin AE1/3 staining in parotid gland.
  • Pancytokeratin often highlights mast cells (non-specifically). Eccrine ducts are also positive in this photo.

Cytokeratins are a family of intermediate filaments that are predominantly found in cells of epithelial origin. Keratins can be divided into two types: acidic cytokeratins (Type I) and basic cytokeratins (Type II).[1]

Practical Uses: Edit

Cytokeratin filaments are located within the cytoplasm of cells. Thus, cytokeratin immunostains should be cytoplasmic stains. Cytokeratin immunostains will stain most carcinomas, carcinoid tumors, epithelial organs, etc. Useful in differentiating sarcomatoid carcinoma from sarcoma.


(Separate pages can be built for each of these antibodies as needed.)

  • Mixture of high molecular weight and low molecular weight cytokeratins. Good as a "pancytokeratin" (that is, it is sensitive as a screening test for detecting the presence of any keratin in a given cell population).

CAM 5.2 small cell ca

Low-molecular-weight cytokeratin CAM 5.2 may produce a distinctive dot-like pattern of positivity in both small cell carcinomas and Merkel cell tumors.

CAM 5.2:Edit
  • Low molecular weight cytokeratin.

  • High molecular weight cytokeratin. Good basal cell marker.
  • Stains basaloid squamous carcinomas, basal-like type ductal carcinoma (aka - triple negative ductal carcinoma), and mesothelioma. It is also used to document squamous differentiation in non-small-cell carcinoma of the lung, a distinction with therapeutic implications.

  • Good marker for lung and breast carcinomas.

Cytokeratin 5/6 (CK5/6) staining basal cells in benign prostate.

Cytokeratin 14 (CK 14):Edit
Cytokeratin 17 (CK 17):Edit
Cytokeratin 18 (CK 18):Edit
Cytokeratin 19 (CK 19):Edit
  • Good marker for colonic adenocarcinoma.
  • Often stains Merkel cell carcinoma with a "perinuclear dot" (Golgi) pattern.


Technical Info/Tips:Edit

Example: Antibody XYZ works best at a 1:200 dilution, or with longer time in steamer, etc.

Pitfalls to Avoid:Edit

  • Some non-epithelial tumors can stain with cytokeratin, particularly sarcomas with epithelioid features (epithelioid sarcoma, epithelioid angiosarcoma, etc, etc).
  • Sarcomatoid carcinomas (e.g. - spindle cell squamous carcinoma) tend not to express keratins as well as their more epithelioid counterparts do. If sarcomatoid/spindle cell carcinoma is suspected, using multiple different keratin antibodies may be useful (sometimes only one of them will stain the tumor).

Useful Articles from the Literature:Edit


  1. Wikipedia:Cytokeratin
  2. Cytokeratin 20 immunoreactivity distinguishes Merkel cell (primary cutaneous neuroendocrine) carcinomas and salivary gland small cell carcinomas from small cell carcinomas of various sites. (AJSP 1997)

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