Invasive mucinous adenocarcinoma of the lung
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Invasive mucinous adenocarcinoma (IMA) of the lung is a subtype of invasive adenocarcinoma of the lung formerly known as mucinous bronchoalveolar carcinoma (BAC). They are more likely to be multicentric and tend to have a worse prognosis than non-mucinous types.
In 2011, the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) 4 introduced a new classification and terminology for adenocarcinoma of the lung. The term bronchoalveolar carcinoma (BAC) has fallen out of favor and "invasive mucinous adenocarcinoma of the lung" is the term currently used for the tumors previously known as "mucinous bronchoalveolar carcinoma (BAC)".
Mucinous carcinomas are commonly multicentric, multilobar, and may show bilateral lung involvement 3,4. These patterns may indicate aerogenous spread 4.
Mucinous carcinomas originate from columnar mucus-containing cells (cf. non-mucinous tumors which arise from club cells (i.e. bronchiolar exocrine cells, formerly known as Clara cells) or type 2 pneumocytes, showing a goblet or columnar cell morphology with abundant intracytoplasmic mucin 3,4. The alveoli are usually filled with mucin 4.
Although also consisting of a mixture of histologic patterns, e.g. lepidic, acinar, papillary, micropapillary, and solid growth, as we observe in the non-mucinous invasive tumors, there is no recommendation to subcategorise the invasive mucinous adenocarcinomas, as the clinical relevance of doing so is still uncertain 4.
Usually characterized by areas of dense pneumonic consolidation, ground-glass opacity and nodules 7. Very rarely may manifest in unusual forms such as thin-walled cysts etc.