It is a common type of lung cancer and its incidence is increasing, particularly in women. Adenocarcinoma is the one cell type of primary lung tumor that occurs more often in non-smokers and in smokers who have quit. Most adenocarcinomas arise in the periphery of the lung.
Bronchioloalveolar carcinoma is considered as a variant of adenocarcinoma.

Histologic subtypes:

  • acinar
  • papillary
  • bronchioloalveolar carcinoma
    • non-mucinous
    • mucinous
    • mixed mucinous and non-mucinous or indeterminate cell type
  • solid adenocarcinoma with mucin
  • adenocarcinoma with mixed subtypes

Rare variants:

  • well-differentiated fetal adenocarcinoma
  • mucinous ('colloid') adenocarcinoma
  • mucinous cystadenocarcinoma
  • signet-ring adenocarcinoma
  • clear cell adenocarcinoma

Cytologic diagnostic features (sputum and bronchial washing)

  • Cell aggregates
  • Large eccentric pleomorphic nuclei
  • Prominent nucleoli
  • Abundant pale vacuolated cytoplasm

Cytologic diagnostic features (FNA and bronchial brushing)

  • Sheets, rosettes and acinar grouing, columnar cells and mucin production
  • Rounded nuclei
  • Prominent nucleoli
  • Abundant pale vacuolated cytoplasm
  • Clean or mucinous background

Differential diagnosis

  • Metastatic adenocarcinoma
  • Reparative/reactive bronchial epithelium
  • Creola bodies
  • Goblet cell hyperplasia
  • Reactive pneumocytes
  • Granulomatous inflammation

The cells of adenocarcinoma, except for poorly differentiated tumors, are more cohesive than those of squamous cell carcinoma. Poorly differentiated adenocarcinoma can be indistinguishable from large cell undifferentiated carcinoma with routine stains, but adenocarcinoma is positive for intracytoplasmic mucin.


  • Cytokeratin 7 +
  • Cytokeratin 5 –
  • Cytokeratin 20 –
  • Neuroendocrine markers +-
  • TTF-1 +


Adenocarcinoma. Malignant cells with round nuclei and large prominent nucleoli forming a gland (acinar formation).
Adenocarcinoma. Pleomorphic malignant cells with round nuclei, vesicular chromatin, and prominent nucleoli.
Adenocarcinoma, poorly differentiated. Discohesive malignant cells with lack of gland formation, vesicular chromatin, and prominent nucleoli.


CAM 5.2



Bronchial brush:

Bronchial brush
Bronchial brush




Squamous cell carcinoma. Numerous keratinized (orangeophilic) and non-keratinized malignant squamous cells dispersed in a background of keratinaceous debris (FNAB).
Squamous cell carcinoma. Malignant keratinized squamous cells with marked pleomorphism and keratinaceous debris.  
Squamous cell carcinoma. Malignant heavily keratinized squamous cells (appearing orangeophilic) with marked pleomorphism in a background of necrotic cytoplasmic fragments.  
Squamous cell carcinoma. Note the extensive tissue necrosis, keratinaceous debris, and a single viable malignant keratinized cell (at 2 o' clock).
Squamous cell carcinoma. An elongated "tadpole-shaped" malignant keratinized cell with heavily keratinized (orangeophilic) cytoplasm.



Occult carcinoma in situ
Occult carcinoma in situ
Occult carcinoma in situ
Occult carcinoma in situ


FNA moderately differ
FNA well differ
FNA well differ
FNA well differ
Transbronchial FNA


Bronchial brush
Bronchial brush
Bronchial brush