One Case Report of Desmoplastic Small Round Cell Tumor of Pleura

BACGROUND: Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive malignancy tumor that often affects the abdomen, especially in males. Extra-abdominal DSRCT is extremely rare. CASE REPORT: Here we report a 33-year-old man diagnosed with DSRCT from pleura without any clinical symptoms. Routine blood examination was normal, and an X-ray examination revealed a chest mass during the routine physical examination. The patient was diagnosed by immunohistochemistry combined with clinical features and imaging examination and nally conrmed by pathology. After the diagnosis, we immediately underwent surgery and postoperative radiotherapy. In the latest follow-up, there was no sign of recurrence. CONCLUSION: Because the disease is asymptomatic at the beginning, it is easy to deteriorate, and there is no specic targeted treatment. Therefore, early diagnosis and treatment are particularly important.


Introduction
DSRCT is a rare, multifocal peritoneal malignancy with the frequently disseminated abdominal disease at presentation, which often occurs in young adults, especially in males. The disease most commonly involves the omentum and peritoneum, followed by the retroperitoneum [1]. Pleural DSRCT is a kind of extra-abdominal DSRCT, which is rare in the lung [2], paranasal sinuses [3], central nervous system [4], soft scalp tissue [5], salivary glands, and pleura [6]. The clinical manifestations are nonspeci c and usually related to the size and location of the tumor. Among them, the translocation of T (11; 22) (P13; Q12) was regarded as its unique marker [6,7]. The disease often signi es a poor prognosis, and anticancer treatment is required, including surgery, chemotherapy, radiotherapy. Combination therapy may prolong survival time [8,9]. Here we report a case about pleural DSRCT.

Case Report
A 33-year-old man was found a mass in the thoracic cavity by chest X-ray during a routine physical examination. He never had any clinical symptoms, such as chest pains and breathing di culties, with no smoking history. Chest CT underwent two weeks later showed there were space-occupying lesions in the right pleural and discontinuity of the fourth anterior rib in the right. Then he was admitted to the department of thoracic surgery. Physical examination reveals normal breath sounds. Tumor markers of lung cancer such as CEA, NES, CY211, SCC were in the normal range. Enhanced Chest CT with threedimensional reconstruction revealed that the tumor appeared as a round-like, sharply de ned lesion in the right thoracic cavity. It was about 4.7×4.2×4.0 cm and slightly hypodense, which was based on the pleura. There was a low attenuation (29 Houns eld Units, HU) on plain examination and heterogeneous enhancement on contrast-enhanced CT, both arterial (47 HU) and venous phases (63 HU) (Fig. 1). The tumor density was uniform, and there was no necrotic cystic change. The fourth ribs had localized bone destruction, which was slightly strengthened after enhancement. PET/CT illustrated a locally hypermetabolic lesion in the right fourth anterior rib (Fig. 2). No abnormalities were found in the enhanced abdominal CT examination. Cranial MRI showed no apparent abnormalities. The patient underwent the Resection of Chest Wall Tumors and a costectomy. The patient was treated by radiotherapy on his second visit. There was no metastasis and recurrence of the tumor. Besides, our team will continue to follow up on patients' tumor metastasis and prognosis.

Availability Of Data And Materials
DSRCT has no speci c diagnostic criteria, and it mainly relies on multiple positive immunohistochemical stains to diagnose the disease. Microscopically, the size of the small tumor cells was consistent, the nucleus was small and deeply stained, and the cytoplasm was sparse, the boundary was not clear, arranged in nests, surrounding sclerotic stroma (Fig. 3).  (Fig. 4). This is similar to the previous results reported by immunohistochemistry [10]. The diagnosis of DSRCT of the pleura was eventually established with no rib invaded.

Discussion
The 5-year survival rate of DSRCT is only 15%. Pathological examinations usually show cell nests with clear outlines in different shapes and sizes and obvious sclerotic stroma around the nests [11]. Histopathological examination can help give a diagnosis [9]. Pleural DSRCT is extremely rare. The previous review about pleural DSRCT studied fteen patients, of which the mean age is 25.5 and maledominated. All patients presented chest or back pain and respiratory symptoms, including dyspnea, cough, pleural effusion. The patient we report didn't have any clinical symptoms though the abnormality was re ected by a chest X-ray. Due to a lack of special clinical manifestations, clinicians may ignore the disease. Histology biopsy is quite important [12]. 10 of 15 patients showed Desmin (+), 4 EMA (+), 4 CD99 (+). The patient we report showed CD57 (+), Bcl-2 (+), CD99 (+), EMA (+), vimentin (+), Desmin (+).
Early diagnosis is di cult because most tumors show nonspeci c gastrointestinal symptoms after a long asymptomatic period [13]. Treatments involve surgery followed by adjuvant radiotherapy or chemoradiotherapy. The survival period reported range from 4 months to 76 months [6]. Combination therapy may prolong the survival time of patients. But it grows rapidly, has a high recurrence rate, and has a poor prognosis, the ve-year overall survival rate is 15% [13]. Therefore, targeted therapies are urgently needed.