Minimally invasive adenocarcinoma (MIA) of the lung is a relatively new category in the classification for adenocarcinoma of the lung. Lesions that fall into this category refer to small solitary adenocarcinomas <3 cm with either pure lepidic growth or predominant lepidic growth with ≤5 mm of stromal invasion.
There is no significant gender predilection, unlike other lung cancer types which are more prevalent in men.
MIAs are localized adenocarcinomas measuring ≤3 cm and demonstrating either pure lepidic or predominant lepidic growth pattern, with neoplastic cells along the alveolar structures and ≤5 mm of stromal invasion 2. These lesions should not show necrosis, lymphatic, vascular, or pleural invasion.
Three histopathological subtypes are recognized 2:
- non-mucinous: by far the most common subtype
- mucinous: goblet cell (mucus-secreting), often multicentric, rare
Similar to the adenocarcinoma in situ, MIA cannot be securely diagnosed without the entire histologic sampling of the tumor 2.
Minimally invasive adenocarcinomas may be associated with PET false-negative results, particularly when the lesions are small. FDG PET/CT is recommended when assessing subsolid ground-glass lung lesions that have a solid component measuring more than 8 mm 4.
Treatment and prognosis
Patients with MIA lesions have near 100% disease-specific survival when they are completely resected 2. Chemotherapy and radiotherapy are treatment alternatives, particularly for those patients that are not surgical candidates.
History and etymology
The entity formerly known as bronchoalveolar carcinoma was first described by Malassez in 1876, as a bilateral, multinodular form of malignant lung tumor 6.
The shifting terminology of non-invasive adenocarcinoma reflects both an increased utilization of immunohistochemical testing, as well as advances in personalized cancer treatment. Beginning with the 1999 World Health Organization guidelines, there has been an attempt to isolate purely non-invasive and minimally-invasive adenocarcinoma from more advanced adenocarcinoma, due to uniquely favourable prognosis in the former 7. Prior to the 2011 IASLC/ATS/ERS update 2, various forms of invasive disease remained lumped into the BAC category. Thus, scrapping the BAC classification was intended to further remove ambiguity.
- 1. Dacic S. Minimally invasive adenocarcinomas of the lung. Adv Anat Pathol. 2009;16 (3): 166-71. doi:10.1097/PAP.0b013e3181a19e3b - Pubmed citation
- 2. Travis WD, Brambilla E, Noguchi M, Nicholson AG, Geisinger KR, Yatabe Y, Beer DG, Powell CA, Riely GJ, Van Schil PE, Garg K, Austin JH, Asamura H, Rusch VW, Hirsch FR, Scagliotti G, Mitsudomi T, Huber RM, Ishikawa Y, Jett J, Sanchez-Cespedes M, Sculier JP, Takahashi T, Tsuboi M, Vansteenkiste J, Wistuba I, Yang PC, Aberle D, Brambilla C, Flieder D, Franklin W, Gazdar A, Gould M, Hasleton P, Henderson D, Johnson B, Johnson D, Kerr K, Kuriyama K, Lee JS, Miller VA, Petersen I, Roggli V, Rosell R, Saijo N, Thunnissen E, Tsao M, Yankelewitz D. International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma. (2011) Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer. 6 (2): 244-85. doi:10.1097/JTO.0b013e318206a221 - Pubmed
- 3. Lee SM, Goo JM, Park CM et-al. A new classification of adenocarcinoma: what the radiologists need to know. Diagn Interv Radiol. 2012;18 (6): 519-26. doi:10.4261/1305-3825.DIR.5778-12.1 - Pubmed citation
- 4. Austin JH, Garg K, Aberle D et-al. Radiologic implications of the 2011 classification of adenocarcinoma of the lung. Radiology. 2013;266 (1): 62-71. Radiology (full text) - doi:10.1148/radiol.12120240 - Pubmed citation
- 5. Kandathil A, Kay FU, Butt YM, Wachsmann JW, Subramaniam RM. Role of FDG PET/CT in the Eighth Edition of TNM Staging of Non-Small Cell Lung Cancer. (2018) Radiographics : a review publication of the Radiological Society of North America, Inc. 38 (7): 2134-2149. doi:10.1148/rg.2018180060 - Pubmed
- 6. Malassez, L Examen histologique d’un cas de cancer encephaloide du poumon (epithelioma). Arch Physiol Norm Pathol 1876;3,353-372
- 7. E. Brambilla, W.D. Travis, T.V. Colby, B. Corrin, Y. Shimosato. The new World Health Organization classification of lung tumours. (2001) European Respiratory Journal. 18 (6): 1059. doi:10.1183/09031936.01.00275301 - Pubmed
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