The specific disease of the left upper lung nodular shadow needs to be determined comprehensively according to the size and nature of the nodule. Nodules are divided into three cases: ground glass nodules, partially solid nodules and solid nodules. If the nodules are smaller than 5mm or less, chronic inflammatory changes are mostly considered, no clinical manifestations, no special treatment is needed, and only dynamic follow-up once a year with high-resolution CT is required. However, if the nodule is larger than 6mm or even 8mm or more, accompanied by pleural pulling sign, short burr, lobar shape, it is necessary to be alert to the possibility of early lung cancer and to give enhanced CT examination of the chest and, if necessary, percutaneous lung aspiration cytohistological examination to understand whether early cancer occurs. A nodular shadow in the upper left lung considers the possibility of chronic inflammation, but if the nodule is significantly enlarged, the possibility of early lung cancer needs to be alerted. Therefore, a combination of enhanced CT of the chest and cytohistological examination is needed to further clarify the diagnosis in order to avoid missed diagnosis and misdiagnosis.