Sessile serrated adenoma

Author: Mikael Häggström

Presentation

• Colorectal polyp

Microscopic examination

The characteristics of sessile serrated adenoma are:

• Sawtooth serrations of the epithelium
• Abundant mucin, similar to hyperplastic polyps
• Basal crypt dilation, with mucous retention, and lateral spread of the crypt bases, commonly described as boot shaped or anchor shaped crypts.

Variations

On low magnification, a sessile serrated adenoma may be flat (left) or protuberant (right):

• File:Histopathology of a flat sessile serrated adenoma.jpg
• File:Histopathology of a protuberant sessile serrated adenoma.jpg

Variations on higher magnification:

• Sessile serrated adenoma with crypt crowding and little serration, loss of cytoplasmic mucin and marked cytological atypia.[2]
  Sessile serrated adenoma with crypt crowding and little serration, loss of cytoplasmic mucin and marked cytological atypia.
• With elongated crypts.[2]
  With elongated crypts.
• Minimal deviation dysplasia: architectural changes are subtle with mild crowding of crypts separated by less lamina propria and showing some degree of disorganization.[2]
  Minimal deviation dysplasia: architectural changes are subtle with mild crowding of crypts separated by less lamina propria and showing some degree of disorganization.
• Minimal deviation dysplasia, showing hypermucinous with some crowding of nuclei, focal hyperchromasia, loss of polarity, mitotic figures (red arrow) and dystrophic mucus cells on the surface (black arrow).[2]
  Minimal deviation dysplasia, showing hypermucinous with some crowding of nuclei, focal hyperchromasia, loss of polarity, mitotic figures (red arrow) and dystrophic mucus cells on the surface (black arrow).
• Adenomatous dysplasia, having a ‘top–down’ dysplasia distribution similarly to conventional adenomas.[2]
  Adenomatous dysplasia, having a ‘top–down’ dysplasia distribution similarly to conventional adenomas.
• Low magnification of sessile serrated adenoma with serrated dysplasia, with small packed glandular structures with abundant eosinophilic cytoplasm.[2]
  Low magnification of sessile serrated adenoma with serrated dysplasia, with small packed glandular structures with abundant eosinophilic cytoplasm.
• High magnification of sessile serrated adenoma with serrated dysplasia: The dysplastic nuclei are round and vesicular with often prominent nucleoli.[2]
  High magnification of sessile serrated adenoma with serrated dysplasia: The dysplastic nuclei are round and vesicular with often prominent nucleoli.
• Sessile serrated adenoma with gastric phenotype, characterized by foveolar mucin and round nuclei.[2]
  Sessile serrated adenoma with gastric phenotype, characterized by foveolar mucin and round nuclei.

Differential diagnoses

• A flat traditional serrated adenoma arising from a sessile serrated adenoma.[2]
  A flat traditional serrated adenoma arising from a sessile serrated adenoma.

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