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Table 2 Histopathological evaluation of vulvar merkel cell carcinomas

From: Clinical features and treatment of vulvar Merkel cell carcinoma: a systematic review

Characteristic n (%)
Histologic finding (n = 17)
 Small cells 12 (70.6)
 High N/C ratio, scant cytoplasm 12 (70.6)
 Nests, islands, trabecular 11 (64.7)
 Hyperchromatic 10 (58.8)
 High mitotic index 8 (47.1)
 Necrosis 6 (35.3)
 Irregular nuclei 4 (23.5)
 Fibrous 4 (23.5)
 Apoptosis 4 (23.5)
 Sheets 3 (17.6)
 Hemorrhage 2 (11.8)
 Ulceration 2 (11.8)
Electron microscopy (n = 7)a
 Dense core granules 6 (85.7)
 Intermediate filaments 5 (71.4)
Immunostaining (n = 14)a
 Neuroendocrine markers
  Chromogranin 7 (50)
  NSE 7 (50)
  Synaptophysin 6 (42.9)
  PGP 9.5 2 (14.3)
 Keratin stains (n = 13)a
  Pancytokeratin AE1/AE3 7 (53.8)
  CAM5.2 4 (30.8)
  Low molecular weight CK 3 (23.1)
  CK7 1 (7.7)
  CK8 2 (15.4)
  CK18 3 (23.1)
  CK19 1 (7.7)
  CK20 4 (30.8)
  Perinuclear dot/granular 7 (53.8)
  1. Abbreviations: CK cytokeratin, N/C ratio nuclear/cytoplasmic ratio, NSE neuron specific enolase, PGP protein gene product
  2. aTotal n, reflected in percentages, is less than 17 due to inconsistent reporting of electron microscopy or positive and negative immunostains