Halo sign and RHS are not disease-specific, and their review of clinical symptoms is essential to narrow the differential diagnosis. Halo signs can result from the spread of inflammatory cells, bleeding, or lepidic growth of some tumors [5]. This aspect is also more reported than primary tumors from secondary tumors to the lung, especially metastases from the GI tract. For example, in the study of Aissaoui et al., it is mentioned that the halo sign in CT of patients who had metastases from the pancreas is more common than other views of the alveolar pattern. This pattern is related to lepidic growth in pathology reports of lung metastases from the pancreas [6]. The growth pattern of lung adenocarcinoma is divided into five types: acinar, papillary, solid, lepidic, and micropapillary. Among these cases, as studies have mentioned, the dominant lepidic form has better 5-year survival than the rest of the growth patterns. Solid and micropapillary growth patterns are worse than others, with a 5-year survival of 55% [7]. The appearance of a halo sign in our patient also had a predominant lepidic growth pattern. Although this growth pattern is in a primary invasive tumor, it is much less likely to metastasize to lymph nodes than solid and micropapillary forms [8]. During the patient's follow-up after about four months, he received his fifth round of chemotherapy. The patient was treated with carboplatin and a pemetrexed chemotherapy regimen.
The prevalence of halo sign and RHS views in patients with Lung adenocarcinoma has not been well investigated, and we have reviewed two retrospective studies that have reported on this. In the study by Edson et al. in 2012, they examined the RHS views in CTscan from 2000 to 2010 in three hospitals from three different countries. They found that among all patients (79 patients) who had this view, two infectious (41 patients) and non-infectious (38 patients) groups were divided. Among 38 patients, only 3 (7.89%) patients were diagnosed with Lung adenocarcinoma [9]. The exciting thing mentioned in this study is that the clinical characteristics of these patients in terms of chronic cough and progressive disease progression are similar to ours. In addition to this view, in the patient's CT scan report, other lesions such as masses, solid nodules, and GGO views have also been seen. Besides having both RHS and halo sign views, our patient also had other lesions, such as cavitary changes and GGO. In another study by Zhang et al. in 2018, they included 226 patients according to the inclusion and exclusion criteria between 2011 and 2017. Of these, 109 patients had lung adenocarcinoma. Only seven patients (6.42%) had a Halo sign. They also mentioned that this view is significantly more in patients with focal organizing pneumonia than in patients with Lung adenocarcinoma [10]. According to the above two studies, it is clear that the prevalence of this disease is rare in patients with a halo sign and even reversed view, and this case is almost unique in that it has both of them together.
In a similar case conducted by Rampinelli et al. in 2014, in ten-year CT scan follow-ups, a 73-year-old woman witnessed changes without increasing or decreasing the size of the RHS form to the halo sign view at three-time points [11]. Considering that our patient was a smoker (35 packs/year) and had a history of exposure to chemicals during his military service, it is possible that asymptomatic changes in his lung occurred years ago. This presence of two views with Each other should be justified in this way. Therefore, more investigations and reports are needed, especially regarding the association of these two views with each other.