title: Immunohistochemistry for CD117 (KIT) is effective in distinguishing cutaneous adnexal tumors with apocrine/eccrine or sebaceous differentiation from other epithelial tumors of the skin.
abstract: BACKGROUND
  The aim of this study was to evaluate the effectiveness of CD117 immunostaining for diagnosing cutaneous adnexal tumors, which has not been previously established.
  
  
  METHODS
  CD117 immunostaining was performed on representative sections of 87 clinicopathologically confirmed cutaneous apocrine/eccrine tumors, 13 sebaceous tumors, 52 follicular tumors, 55 keratinocytic tumors, 24 metastatic tumors of the skin of known origin and 1 mammary Paget disease. Staining of 5-50% of cells was considered focally positive, and staining of 51-100% of cells was considered diffusely positive. Staining intensity was semi-quantitatively graded as weak, moderate or strong.
  
  
  RESULTS
  A total of 82 (94.3%) tumors with apocrine/eccrine differentiation were CD117-positive, whereas one mucinous carcinoma, one apocrine carcinoma, and three primary cutaneous extramammary Paget diseases were CD117-negative. For most positive cases, staining was diffuse (64/82 cases) and moderate to strong in intensity (74/82). Twelve (92.3%) sebaceous tumors were CD117-positive, showing mainly focal (9/12) and weak (7/12) positivity. Of the 52 follicular tumors, all 4 cases of pilomatricoma and other 5 tumors were positive for CD117. Of the 55 keratinocytic tumors, only 2 cases were CD117-positive. The 24 metastatic tumors and mammary Paget disease were CD117-negative.
  
  
  CONCLUSIONS
  CD117 may be useful for the differential diagnosis of cutaneous adnexal tumors.
authors: Department of Diagnostic Pathology, Kainan Hospital, Yatomi-city, Aichi, Japan.
authors: Keisuke
authors: K
authors: Goto
mesh_terms: D000291:Adnexal Diseases / Q000175:diagnosis* / Q000201:enzymology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D009375:Neoplasms, Glandular and Epithelial / Q000201:enzymology / Q000473:pathology; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000201:enzymology*
chemical_list: D019009:Proto-Oncogene Proteins c-kit
keywords: c-KIT protein; immunohistochemistry; skin neoplasms