51. Lepidic adenocarcinoma

Page created on December 4, 2018. Last updated on January 17, 2019 at 17:27

Staining: HE

Organ: Lung


The slide has two zones. The lower zone shows healthy, unaffected lung parenchyme.

The upper zone shows normal structure of the alveoli, however the insides of the alveoli are lined by tumor cells.

Diagnosis: Lepidic adenocarcinoma


  • Genetic mutations
    • EGFR
    • KRAS
    • ALK
    • PDL-1


Five types of lung adenocarcinomas exist:

  • Papillary type
  • Acinar type
  • Solid type
  • Micropapillary type (worse prognosis)
  • Lepidic type (best prognosis)

This histology slide shows a “lepidic” growth pattern, which is the pattern where the tumor cells line the alveolar walls instead of invading the interstitium. The alveolar structure is therefore maintained.

It’s technically an adenocarcinoma in situ because it hasn’t passed the basement membrane yet.

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2 thoughts on “51. Lepidic adenocarcinoma”

  1. Infiltrative neostroma (darker area in the middle) destroying alveolar structure means that it is invasive with metastatic potential, and not in situ as it may appear in the rest of the slide.

    1. Hmm, both Robbins (p. 508) and the lecture (slide 8) on lung tumors states that the lepidic growth pattern is an adenocarcinoma in situ and by definition don’t destroy alveolar structure. However, I agree that the dark part of the slide looks like it shows some destruction.
      The lecture also states that tumors are often not just one single type but rather a combination of more types, so that could be the case here, I don’t know.

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