18F-FDG PET/CT Revealed of Rare Primary Lyphoepithelionma-Like Carcinoma of the Lung: A Case Report and Literature Review

Xue Liu^1,2, Tao Jiang¹ and Bao Zhang^1*
*Correspondence: Bao Zhang, Department of Nuclear Medicine, The First Pepole’s Hospital of Huaihua City, Hunan, China, Email:

Keywords

Lyphoepithelionma-like carcinoma ● Lung cancer ● 18F-FDG PET/CT ● Case report

Introduction

Lymphoepithelioma-like carcinoma (LELC) is a rare type of cancer that usually occurs in the pharynx and foregut-derivative organs, including the salivary glands, thymus, stomach and liver [1]. Primary lung LELC is a rare subtype of non-small cell lung cancer, accounting for about 0.92% of other lung cancer types [2]. Lymphoepitheliomatoid carcinoma of the lung was first reported by Begin LR et al. in 1987[3].

Lung LELC is a large, centrally placeholder tumor with a smooth edge in imaging[4]. The diagnosis of lung LELC is mainly dependent on pathological and immunohistochemical results. Histologically, it is difficult to differentiate lung LELC from metastatic nasopharyngeal carcinoma. The diagnosis must be combined with the patient's history, endoscopy or magnetic resonance imaging (MRI) to evaluate whether the tumor is metastasized from nasopharyngeal tumor. Primary lung LELC can be diagnosed after exclusion of nasopharyngeal malignancy as a source. ¹⁸F-FDG PET/CT examination has important application value in the diagnosis of pulmonary nodules or masses. Therefore, this study conducted a brief review of relevant literature.

Case Report

A 44-year-old woman was hospitalized for one year with intermittent coughing and expectoration. She has no history of smoking or previous medical conditions. Laboratory tests for tumor markers showed the following results: neuron-specific enolase was 17.16ng/ml (0-16.3), non-small cell lung cancer associated antigen was 10.49ng/ml (0-3.3), squmaous cell carcinoma antigen was 1.74ng/ml (0-2.5), tumor specific growth factor 67.1U/L (0-68), carcinoembryonic antigen <0.5ng/ml (0-5). DNA test positive for Epstein-Barr (EB) virus. All the indicators related to mycobacterium tuberculosis were negative.

Chest CT showed a soft tissue mass with the size of 6.4cm×7.6cm×8.7cm in the left lower lobe of the lung and non-uniformity of image density. There were patchy and cable-like shadow around the mass. Part of the bronchus in the lower lobe of the left lung was compressed and occluded. On contrastenhanced CT, the mass was inhomogeneously enhanced. The left pleura is thickened with a small effusion in the left pleural cavity. Therefore, this mass was considered a malignant neoplasm of the lung.

To further evaluate the nature of mass and the patient's whole-body condition, ¹⁸F-FDG PET/CT examination was performed. On the maximum density projection(MIP) of the 18F-FDG PET/CT, there was a mass of abnormal increased glucose metabolism on the left side of the chest. On cross-sectional view, the lesion had significant uptake of FDG and maximum standard uptake value (SUVmax) was 10.7. Bilateral hilar and mediastinal lymph nodes were not enlarged and FDG uptake was not abnormal. There was no abnormality in FDG uptake in the remaining tissues and organs of the body. Subsequently, the patient underwent puncture of the lesion. Microscopic pathology findings showed that the cancer cells were arranged in irregular nest-like structures, with elliptic nuclei, fine chromatin, interstitial fibrosis, coagulant necrosis and granulomatous nodules, and a large number of lymphocytes infiltration. The immunohistochemical results were as follows: CK(+), P63 (+), P40 (+), TTF-1 (-). Tissue In situ hybridization immunohistochemistry: EB virus (+). Based on biopsy and immunohistochemical results, the histological changes of this mass were consistent with lyphoepithelionma-like carcinoma (LELC).

In order to exclude the lung lesion from nasopharyngeal carcinoma metastasis, the patient underwent nasopharyngeal MRI examination and found no abnormality. In addition, the otolaryngologist examined the nasopharynx by fiberscopy and did not find any abnormalities. We also re-read the ¹⁸F-FDG PET/ CT images to suggest normal glucose metabolism in nasopharyngeal tissue. Ultimately, the patient was diagnosed with primary lung lymphoepithelioma-like carcinoma, the TNM stage was considered as T4N0M0 IIIA. Due to the large size of the lesion, the patient and his family refused surgical treatment and requested conservative treatment. Therefore, the patient received systemic chemotherapy. The patient's lung CT reexamination indicated that the lesion was significantly smaller than before after 2 months treatment, indicating that the therapy was effective (Figure 1).

Discussion

Lymphoepithelioma-like carcinoma, originally seen in the nasopharynx, refers to undifferentiated carcinoma dominated by lymphocyte infiltration [2]. A primary lung cancer that mimicking undifferentiated Nasopharyngeal carcinoma (NPC) known as lymphoma epithelial tumor-like carcinoma was first reported in 1987 by Begin LR et al.[3] in 1987 first reported a primary lung cancer similar to undifferentiated nasopharyngeal carcinoma called lymphoma epithelial tumor-like carcinoma. Some studies believe that the average age of the disease is younger than that of other types of lung cancer, and there is no significant gender difference, and the incidence of non-smokers is higher [4]. Almost all of the Chinese patients (>90%) had EB virus-positive tumors [4]. The clinical symptoms of lung LELC are non-specific, and cough, sputum and chest pain are common [5-7]. The first clinical symptoms of the patient we reported were cough and expectoration, without any symptoms of infectious diseases.

Lung LELC is no significant specificity on imaging and tends to be confused with other lung malignancies [4]. According to previous literature, the maximum diameter of lung LELC varies from 1.5 to 8cm. Most of the tumors were isolated, mostly in the right lung. In this case, the lesion was located in the lower lobe of the left lung with a maximum diameter of 8.7cm. The diagnosis of lung LELC is mainly dependent on pathological and immunohistochemical results. Histologically, the typical lung LELC consists of undifferentiated carcinoma cells with ill-defined cytoplasmic borders arranged in syncytial sheets and nests [2]. The tumour cell nuclei are round, oval or elongated with mildly irregular nuclear outline, vesicular chromatin and distinct nucleoli [8]. However, it is difficult to differentiate lung LELC from metastatic nasopharyngeal carcinoma. The diagnosis must be combined with the patient's history, endoscopy or MRI to evaluate whether the tumor is metastasized from nasopharyngeal tumor. Primary lung LELC can be diagnosed after exclusion of nasopharyngeal malignancy as a source [2].

¹⁸F-FDG PET/CT examination has important application value in the diagnosis of pulmonary nodules or masses. However, the incidence of lung LELC is low and 18F-FDG PET/CT has been used to evaluate the disease in fewer cases. Therefore, this study conducted a brief review of relevant literature. We performed electronic literature searches of the PubMed, Embase and Cochrane Library databases for English-language articles from the earliest available date of indexing through 25 June 2021. The following key words were used for the selection of studies: FDG, PET, LELC, lung, pulmonary. All English case reports of FDG PET/CT for lung LELC were included in the analysis. Nine case reports were retrieved. Two cases reported by Japanese authors [9, 10] were excluded because the original texts were not available. Finally, only seven articles [5-7, 11-14] met the criteria, including four from China [11-14] and three from Turkey [5-7]. Five patients tested positive for Epstein-Barr virus (Table 1).