Differential expression of S100 protein subtypes in malignant melanoma, and benign and malignant peripheral nerve sheath tumors.
BACKGROUND
Desmoplastic melanoma (DM) may simulate various benign and malignant lesions, including benign peripheral nerve sheath tumors (BPNSTs) and malignant peripheral nerve sheath tumors (MPNSTs). The latter case is diagnostically challenging because DM generally show only S100 protein expression but no reaction to melanocytic markers. S100 family of proteins consists of over 20 members. We report on S100 subtypes in malignant melanomas (MMs), and BPNSTs and MPNSTs to investigate differential expression.


METHODS
S100A1, S100A2, S100A4, S100A6 and S100B immunostains were performed on 80 MMs including conventional and desmoplastic types, 86 BPNSTs and 77 MPNSTs.


RESULTS
S100A1 expression was seen in > 91% of MMs in a diffuse reaction, whereas BPNSTs showed focal or no reaction. Sixteen percent of MPNSTs focally expressed S100A1 except for one case with diffuse reaction. S100A2 staining was negative or focal in all three groups whereas S100A4 reaction was variable in all three. S100A6 was diffusely expressed in MMs, BPNSTs and MPNSTs. S100B was stained diffusely in MMs and BPNSTs, but its reaction was observed in 30% of MPNSTs in a focal fashion.


CONCLUSIONS
S100A1 expression was diffuse in most of MMs but absent or focal in BPNSTs and MPNSTs. This may be helpful to distinguish between the two entities.
Nonaka
Daisuke
D
Department of Pathology, New York University School of Medicine, New York, NY 10016, USA. daisuke.nonaka@med.nyu.edu
Chiriboga
Luis
L
Rubin
Brian P
BP
D014408:Biomarkers, Tumor / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D003593:Cytoplasm / Q000378:metabolism / Q000473:pathology; D019085:Fluorescent Antibody Technique, Direct; D006801:Humans; D007124:Immunoenzyme Techniques; D008545:Melanoma / Q000378:metabolism* / Q000556:secondary; D018317:Nerve Sheath Neoplasms / Q000378:metabolism* / Q000473:pathology; D009442:Neurilemmoma / Q000378:metabolism / Q000473:pathology; D018318:Neurofibroma, Plexiform / Q000378:metabolism / Q000473:pathology; D009418:S100 Proteins / Q000378:metabolism*; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology; D046888:Tissue Array Analysis
D014408:Biomarkers, Tumor; D009418:S100 Proteins