Adenocarcinomas in situ (AIS) of the lung refer to a relatively new entity for a pre-invasive lesion in the lung. This entity partly replaces the noninvasive end of the previous term bronchoalveolar carcinoma. Adenocarcinoma in situ is defined as a localised adenocarcinoma of <3 cm that exhibits a lepidic growth pattern, with neoplastic cells along the alveolar structures but without stromal, vascular, or pleural invasion 1.
AISs are localised adenocarcinomas of ≤3 cm, with no growth pattern other than lepidic, with neoplastic cells along the alveolar structures but without stromal, vascular, lymphatic, or pleural invasion, and no features of necrosis 6.
There are three histopathological subtypes, the most common is non-mucinous, with mucinous or mixed subtypes being rarely found.
While adenocarcinoma in situ is usually seen as a pure ground-glass nodule or a part-solid lung nodule, there can be overlap among the imaging features of atypical adenomatous hyperplasia, adenocarcinoma in situ, and invasive adenocarcinoma of the lung 1.
Adenocarcinomas in situ are commonly associated with PET false-negative results. FDG PET/CT is recommended when assessing subsolid ground-glass lung lesions that have a solid component measuring more than 8 mm 5.
Treatment and prognosis
Adenocarcinoma in situ carries an excellent prognosis, with reported survival rates of 100% following complete tumor resection 6.
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- 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. 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
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