S-100 by IHC

Alphabetical Test listing

S-100 by IHC-12376 - Technical only, 12379 - Technical & interpretation

S-100 by IHC
12376 - Technical only, 12379 - Technical & interpretation
  • All IHC stains will include a positive control tissue
  • Using polyclonal antibodies, a variety of human tissue types are recognized:
    • αα– myocardial and skeletal muscle cells
    • αβ– glial cells, melanocytes, chondrocytes, and adnexal glands
    • ββ– Schwann cells and Langerhans cells
  • Pattern of S100 reactivity:
Normal cells Tumors
Melanocytes Melanomas and various nevi
Astrocytes Gliomas
Neurons, neuroblasts Neuroblastomas
Chondrocytes Chondrosarcoma and chondromas
Schwann cells Schwannoma, granular cells tumor, neurofibroma
Fat cells Liposarcoma
Myoepithelial and duct cells Subsets of salv gland, sweat gland, and breast tumors
Langerhans cells Histiocytosis X
Histiocytes and reticular cells Malignant histiocytosis
Notochord remnant cells Chordomas
  • S-100 protein is the most sensitive marker for melanoma; it stains amelanotic melanomas more strongly than pigmented tumors and usually detects desmoplastic and spindled melanomas (which are usually HMB45 negative)
  • For melanomas, order both S-100 and HMB45 (if lesion is heavily pigmented, consider specifying the alkaline phosphatase (red) staining method.

Submit a formalin-fixed, paraffin embedded tissue block


Formalin-fixed, paraffin embedded (FFPE) tissue block


FFPE tissue section mounted on a charged, unstained slide


Ambient (preferred)

  • Unlabeled/mislabeled block
  • Insufficient tissue
  • Slides broken beyond repair
AHL - Immunohistochemistry
Mo - Fr
1 - 2 days

Immunohistochemical staining and microscopic examination


If requested, an interpretive report will be provided



  • S-100 is a calcium binding protein that is composed of two subunits (alpha or beta) found in 3 different dimer forms.

 Staining pattern

  • Cytoplasmic and nuclear based staining (should see both)

88342 - 1st stain
88341 - each additional stain