Recommended nomenclature for reporting pulmonary adenocarcinoma and related lesions in surgical resection specimens and the equivalent nomenclature for use in small diagnostic samples
| Adenocarcinoma diagnosis nomenclature in surgical resection specimens | Adenocarcinoma diagnosis nomenclature in small samples (biopsy and cytology) |
|---|---|
| Atypical adenomatous hyperplasia (AAH) | ‘Atypical bronchioloalveolar proliferation’. AAH diagnosis not possible in small samples |
| Adenocarcinoma in situ (AIS) | ‘Lepidic pattern adenocarcinoma’ on biopsy. In situ disease can be neither confirmed nor assumed |
| Minimally invasive adenocarcinoma (MIA) | ‘Adenocarcinoma’. MIA not possible in small samples Depending on sample, lepidic or other patterns may be seen (see below) |
| Invasive Adenocarcinoma Lepidic predominant Acinar predominant Papillary predominant Micropapillary predominant Solid (with mucin) predominant | Adenocarcinoma’.‘ Depending on sample, pattern may be seen, but the reliability of this observation is unknown. ‘Non-small-cell carcinoma, probably adenocarcinoma’ (after predictive IHC) Some cases will remain ‘NSCLC-NOS’ if IHC is not predictive |
| Adenocarcinoma variants Invasive mucinous* Colloid pattern Enteric† Foetal (low and high grade) | ‘Adenocarcinoma’ Variant histology may be seen and pattern described in small samples, but reliability unknown. Be aware of possible extrapulmonary metastases mimicking these |
Signet-ring cell and clear cell features no longer indicate variants. They are simply cellular changes, not unique to adenocarcinoma, worthy of mention in the report. The possibility of metastatic disease should be considered. Signet-ring cells raise possibility of ALK gene rearrangement.
*Formerly known as mucinous BAC, these lesions are nearly always multifocal, with distinct radiological features mimicking pneumonia.
†A rare tumour with an IHC phenotype identical to colorectal carcinoma. Clinicopathological correlation is required for diagnosis.
BAC, bronchioloalveolar carcinoma; IHC, immunohistochemistry; NSCLC, non-small-cell lung carcinomas.