Multiple primary lung cancer is rare, with a reported incidence of 3.7% to 8.0%. This number has increased due to the development of clinical diagnostic techniques . Like single lung cancer, MPLC occurs at an average age of 63.4 years, and 36.7% of patients are female . It usually occurs unilaterally . In this case, CT demonstrated that the lesions occurred in both lobes of the lungs.
It is repored that squamous cell carcinoma plus squamous cell carcinoma is the most common type [5,6]. The present case is composed of an adenocarcinoma and adenoid cystic carcinoma, which are rarely reported. Adenoid cystic carcinoma of the lung is a rare type of tumor that makes up 0.04–0.2% of primary pulmonary tumors. It more commonly involves the salivary glands in the head and neck . Histologically, this tumor exhibits three main growth patterns: the cribriform, tubular, and solid patterns. ACC of the lung is characterized by its expression of myoepithelial markers, which include P63, SMA, C-kit, and S-100 protein. Once pulmonary ACC is identified, it becomes essential to determine whether the lesion represents distant metastasis or primary lung cancer . In order to rule out the possibility of metastatic diseases, we conducted a general otorhinolaryngological examination to try to seek a primary salivary gland tumor. It turned out that there is no abnormalities in the ears, nose and throat.
Furthermore, it is also critical and challenging to distinguish whether multiple lung cancers are independent or related. That is, to differentiate multiple primary cancers from intrapulmonary metastases. The former is typically treated surgically, and the prognosis is good. However, the latter involves systemic chemotherapy, and the prognosis is poor . The American Joint Commission on Cancer has adopted comprehensive histologic assessment (CHA) as a diagnostic criterion . The proposal of CHA provided a new basis for differential diagnosis. The contents of CHA include the percentage of various histologic subtypes, nuclear features, and stromal characteristics. This is particularly useful while evaluating multiple lesions that exhibit the same tissue type. The principle of immunohistochemistry technology is that antigen and antibody can combine specifically, so as to characterize and locate the specific antigen or antibody in tissues and cells. It can be used as a first-line method for differentiation and diagnosis in cases where imaging cannot distinguish between two tumor types. In addition, in clinical practice, the integration of radiology, histopathology, and integrated genomic features by multidisciplinary teams promotes a more accurate diagnosis of MPLC . Thus, to further identify whether it was a primary tumor or metastatic cancer, we used histopathology to identify the two lesions from the source. As in this case, the nodule in the left main bronchus expresses both basal cells and glandular epithelial markers, leading to the diagnosis of adenoid cystic carcinoma of origin. The right lung mass expresses TTF-1 and NapsinA, which we confidently diagnosed as originating from adenocarcinoma.
Unlike intrapulmonary metastasis, MPLC often presents as an early-stage disease ; thus, surgical treatment should be considered as the modality of choice for managing MPLC patients . To date, radical surgery is the primary therapy for MPLC. However, the optimal extent of surgical intervention has not yet been standardized . In Tie’s article, he put forward anatomical resection, which is defined as lobectomy, double lobectomy, and pneumonectomy plus lymph node dissection, with adequate pulmonary reserve. When the patient has limited lung function, lobectomy with sublobectomy or sublobectomy alone is also possible. Among these, anatomic segmental resection is preferred for sublobar resection.Unfortunately, due to the distant metastases in our patient, we had to treat her conservatively. For the early patients who are medically inoperable in clinical, experts have proposed the treatment method of stereotactic body radiotherapy (SBRT). Its effectiveness and security have been proved . However, the efficacy of SBRT for patients in advanced stage needs further research.