Lepidic-predominant adenocarcinoma of the lung

Lepidic predominant adenocarcinoma (LPA) of the lung, formerly known as non-mucinous bronchoalveolar carcinoma, is a subtype of invasive adenocarcinoma of the lung characterised histologically when the lepidic component dominates in an invasive adenocarcinomacomprises the majority of the lesion.

Terminology

In 2011, the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) introduced a new classification and terminology for adenocarcinoma of the lung.  The term bronchoalveolar carcinoma (BAC) has been extinctretired, and it is recommended that all invasive adenocarcinomas be classified in terms of the "predominant" comprising histology.

The term lepidic means "crawling", and is used by pathologists to describe growth of neoplastic cells "crawling" along normal lung architecture ².

The category of 'lepid predominant adenocarcinoma' now replaces 'non-mucinous bronchoalveolar carcinoma' of the lung; all mucinous tumors are placed in a separate category.

Pathology

Invasive adenocarcinoma is defined as a lesion with >5 mm of invasion into the normal surrounding lung (i.e. lymphatics, pleura, or blood vessels) and/or the presence of tumor necrosis on the basis of histology of the surgical resection specimen. Non-mucinous disease is further assessed for any histologic patterns within the lesion (lepidic, acinar, papillary, micropapillary, and solid growth), and the "predominant" subtype is reported ².

Thus, lepidic predominant adenocarcinomainvasive adenocarcinomas show a predominance of the lung now replaces the tumours previously known as non-mucinous bronchoalveolar carcinoma.

Pathology 

These tend to be non-mucinous lesionsbland pneumocytic-type neoplastic cells with > 5mm of invasiongrowth along normal structures e.g. This is usually a histological diagnosis and is applied when the lepidic component dominates in an invasive adenocarcinoma lesionalveoli.