Adenocarcinoma

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.