Until now, there has been few systematic reports focusing on pulmonary sarcomatoid carcinoma due to the inherent rarity of this disorder. The concept of PSC was first proposed by German pathologist Virchow in 1864. the WHO classified PSC as a subgroup of non-small cell tumors containing sarcomatoid cells or sarcomatoid differentiation[6, 8, 9]. PSC is a rare and accounts for only a small percentage of all lung malignancies. PSC tends to occur in elderly men at the age of 65–75, mostly smokers[2]. The clinical features of PSC are similar to other forms of non-small cell lung cancer, but it is more aggressive and often presents with larger tumors[10]. Central form PSC often present with cough, hemoptysis, fever and so on. In this study, we reported the co-existence of PSC and aspergillosis. Tumor was growing in the left bronchial with aspergillosis on the mass surface in this patient, which may be a rare condition in diagnosis, and provide an opportunity to recognize the co-existence of PSC and aspergillosis. It might be due to 8-year COPD history for which he frequently used of broad-spectrum antibiotics and glucocorticoids, leading to low immunity. Clinicians should be aware of these similarities between PSC and aspergillosis when investigating patients with lung mass.
In the case, this PSC patient was initially misdiagnosed as aspergillus disease through bronchoscope pathological cytological examination, but further larger tissue samples from lung puncture eventually corrected it by histopathology and specific immunohistochemical staining. Hence, if an inadequate specimen is obtained, the malignant disease may not be diagnosed. Bronchoscopy biopsy and sputum cytology showed a low positive rate in PSC diagnosis[11]. It is very important to obtain enough large specimens used for immunohistochemistry and microscopy to diagnose accurately. A definitive diagnosis needs to be made by combining clinical features, immunohistochemistry and molecular biological behavior. In this study, the patient's sputum exfoliated cells and bronchoscopy biopsy did not find tumor cells. Diagnosis is mainly based on lung puncture pathology. Microscopically, a poorly differentiated sarcomatoid components is seen. Immunohistochemistry showed epithelioid and sarcomatoid markers, that is CK(+), Vim(+), which was also an important basis for diagnosis[12].
Pulmonary sarcomatoid carcinoma, as a group of lung carcinomas, is poorly differentiated and highly aggressive and with poor prognosis. It is prone to recurrence after surgery and is insensitive to platinum-based chemotherapy. PSC has limited therapeutic options[4].Next generation sequencing (NGS)technology can analyze genome-wide molecules condition in PSC which is related to tumorigenesis and prognosis. In general, NGS is recommended for PSC patients if it is available, especially for advanced PSC patients, which may provide new treatment strategies [7][13]. More and more research has found that PSC often has potential targetable genomic alterations[14, 15]. By high-throughput sequencing technology, it is found that the most common mutations in PSC are KRAS (34.4%) and TP53 (73.6%). The skipping mutations in MET exon 14 are also frequent (up to 13%) and are associated with the occurrence of PSC[14]. MET signaling pathways activation is generally related with EMT, which is thought to be the driving mechanism for the occurrence and progression of PSC[16], thus Crizotinib may be effective for MET positive PSC patients. The EGFR mutation rate in PSC is significantly lower than other NSCLC groups, and the efficacy of Epidermal growth factor receptor inhibitors is also inconsistent in positive PSC patients. In addition, Studies have found that there is high level expression of PD-L1 and high tumor mutation burden (TMB) in PSC, immunotherapy shows encouragingly efficacy in PSC patients[17–19] and Perbolizumab may be an option for patients with PD-L1 expression greater than 50%[20]. In the case, the PSC patient with EGFR mutation also did not respond well to Conmana. Targeted drugs need a lot of clinical trials to give us a definitive answer. Targeted therapy and immunotherapy are new directions in the treatment which have bring hope for advanced PSC patients. In addition to these therapies, more promising treatment strategies for PSC are needed to be further explored.