Depending on the Breslow depth of the primary
melanoma, sentinel lymph node biopsy is considered as standard of care for the staging of cutaneous
melanoma, and is one of the most important prognostic factors. The histologic analysis of these specimens becomes difficult to interpret when benign intranodal nevic cells mimic
metastases.
Insulin-like growth factor-II messenger RNA (
mRNA)-binding protein-3 (IMP3), also known as K homology domain-containing
protein overexpressed in
cancer or L523S, is a member of the
insulin-like growth factor-II mRNA-
binding protein family and has been shown to have diagnostic utility in distinguishing cutaneous
melanoma from benign
nevi. In this study, 43 sentinel lymph node biopsy specimens, including 13 with benign intranodal
nevi and 30 with metastatic
melanoma (two cases containing both benign
nevi and metastatic
melanoma), from 41 patients were immunohistochemically analyzed with a
monoclonal antibody against IMP3. None of the benign intranodal
nevi expressed IMP3, whereas 21 out of 30 (70%) of the lymph nodes containing metastatic
melanoma did. It seems that IMP3 is helpful in distinguishing benign intranodal
nevi from metastatic
melanoma in sentinel lymph node biopsy specimens, and could be a valuable diagnostic adjunct in sentinel lymph node biopsy assessment in which questions arise as to the
malignancy of the melanocytes present.