Surgical Pathology Criteria

Adenoma of the Colon and Rectum

Differential Diagnosis

Tubular vs. Villous Adenomas are distinguished based on % of adenoma surface displaying tubular and villous formation
  Tubular Adenoma Tubulovillous Adenoma Villous Adenoma
Tubules >80% 20-80% <20%
Villi <20% 20-80% >80%
  • Length of villi must be ≥2x normal mucosal thickness
  • Tubules vs. villi may be easier to distinguish on en face sections (see Diagnostic Criteria at left for description)
  • High vs. Low Grade Dysplasia in an adenoma are distinguished based on architecture (usually) or cytology (see Grading for criteria)

    Hyperplastic Polyp Tubular Adenoma
    Lacks cytologic dysplasia Requires cytologic dysplasia
    Proliferative zone restricted to base Proliferative zone starts at the surface
    Gland lining cells mature at the surface No surface maturation
    Deep proliferative zone of HP can resemble TA; the surface must be examined to make the distinction in many cases

     

    Traditional Serrated Adenoma Colorectal Tubular Adenoma
    Serrated architecture Lacks prominent serration
    Complex buds (ectopic crypts) all communicate with lumen Complex glands may not always communicate with surface
    CK20 restricted to luminal surfaces CK20 staining random

     

    Filiform Variant of Traditional Serrated Adenoma Villous Adenoma
    Villi lined by complex serrations Villi lined by relatively uniform columnar cells
    Frequent edematous bulbous ends on villi Villi typically pointed

     

    Usual Colorectal Adenoma Sessile Serrated Polyp / Adenoma
    Cytologic dysplasia throughout Cytologic dysplasia, if present, is a focal lesion
    Typically complex architecture Basal dilation and flattening, boot or inverted T shaped, but overall, crypts are vertically arranged and not complex
    Lacks serrations Prominent serrations

     

    Mucosal Prolapse / Cloacogenic Polyp Colorectal Adenoma
    Nuclear atypia most prominent deep in the lesion with surface maturation Nuclear atypia involves surface of polyp
    Nuclei usually enlarged but round and not stratified and not densely packed Nuclei elongated, hyperchromatic, densely packed and frequently stratified
    Apoptosis not prominent Prominent apoptosis

     

    Sporadic Juvenile Polyp Tubular Adenoma
    Lacks cytologic dysplasia Requires cytologic dysplasia
    Prominent cystically dilated glands Cystic dilation usually not prominent
    Abundant inflamed stroma Inflamed stroma usually not prominent

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