Clinicopathologic features and genomic analysis of pulmonary blastomatoid carcinosarcoma

Three cases of BCS were collected from the department of pathology of Shanghai Chest Hospital. These specimens were surgically resected between May 2012 and January 2018. All cases were processed and taken after routine internal perfusion and external fixation by 10% buffered formalin solution. Basic information of patients, grossing photographs and imaging data were reviewed from archived documents and medical records. Patients were routinely screened by chest computed tomography (CT) every six months. The median clinical follow-up time was 68 months (range 13 to 72). The last follow-up time was February 2019. Oncogenic driven gene mutation statuses, including Epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK) and ROS1 rearrangements were routinely detected and confirmed repeatedly by amplification refractory mutation system (ARMS) and/or fluorescence in situ hybridization (FISH) methods. All 3 patients had wild-type EGFR, ALK and ROS1. The pathological and clinical staging were introduced according to the recommendation of the seventh edition of lung cancer [9]. Diagnosis and recognition of H-FLAC and L-FLAC were reevaluated according to the 2015 WHO classification of lung tumors by three experienced pathologists (JZ, JKZ and YCH). Our study was approved by the ethics committee (informed consent for patient biopsy) of Shanghai Chest Hospital of Shanghai Jiao Tong University. Informed consent for surgical operation were signed by all three patients. All patients agreed to participate in the study with all relevant personal and clinical information. Written informed consent was obtained from patient 1 and verbal informed consents were obtained from immediate family members of patient 2 and patient 3 for publication of scientific papers in succession.

Immunohistochemistry was performed on 4-μm dewaxing tissue slices by using the auto-stainer GI100 (DAKO OMNIS) and automated stainer (Ventana Benchmark XT; Roche Ventana) following the manufacturer’s instructions. The diagnostic primary antibodies are listed in Table 1. Normal lung tissue in specimen sections provided better negative and positive controls for panCK, TTF-1, vimentin, α-SMA and Ki-67. For each batch of samples, appropriate positive and negative controls were set according to the instructions of each antibody and the experience of our immunohistochemical laboratory. The titers of all antibodies were verified and approved by strict laboratory procedures.

The patients included two males and one female, with a mean age of 54 (ranged from 38 to 78). Patient one and patient two underwent lobectomy and lymph node dissection, and the first patient received three cycles of chemotherapy subsequently. The third patient underwent three courses of neoadjuvant chemotherapy followed by surgical resection. Detailed information was summarized in Table 2. CT scans revealed that all three tumors showed well-circumscribed mass. The third tumor presented a fibrous pseudocapsule and obvious hemorrhagic necrosis due to the neoadjuvant chemotherapy. Histologically, the epithelial component in patient one consisted of most H-FLAC and fewer L-FLAC components with characteristic squamoid morule structure. The mesenchymal components were mixed with epithelium, and the cells showed a short spindle or oval morphology in the myxoid background (Fig. 1). H-FLAC showed obvious nuclear atypia and mitotic activity with comedo-like necrosis. The epithelial component in patient two consisted of pure H-FLAC and the small oval stromal cells in case two were tightly arranged with high nucleocytoplasmic ratio. These cells showed no evidence of histological and immunohistochemical differentiation (Fig. 2). In patient three, the epithelial was composed of labyrinth-like glands with nucleus locating at the lateral margin and the supranuclear vacuoles toward the base. Besides, some dilated and elongated glands with dirty necrosis resembling the morphology of pulmonary enteric adenocarcinoma. The stromal elements were spindle or fibroblast-like, arranged in bundles, but structurally and morphologically insufficient to diagnose fibrosarcoma, malignant peripheral nerve sheath tumor and other special differentiated mesenchymal tumors (Fig. 3). No conventional high-grade lung adenocarcinoma or other histological non-small cell lung cancer variants were found in all three tumors. Giant cells with bizarre nucleus were not present in any of samples of mesenchymal components.

The results of immunohistochemistry were summarized in Table and Fig. 4. Only the squamoid morule cells of the L-FLAC component but not the surrounding stromal cells in patient one showed nuclear/cytoplasmic localization of β-catenin protein. All H-FLAC and mesenchymal components showed membranous/cytoplasmic dot positive. TTF-1 was positive in epithelial components of the first two tumors. Neuroendocrine markers (CD56 and Synaptophysin) showed various degrees of expression in both epithelial and mesenchymal cells, but nuclear immunostaining for INSM1 was not detected. PanCK was positive in epithelial cells and vimentin was diffusely positive in mesenchymal components. Mesenchymal markers (SMA, MyoD1) were negative in mesenchymal components. S-100 was partially expressed in mesenchymal cells in the third tumor. The proliferation index of epithelial components (30–80%) were significantly higher than that of mesenchymal cells (15–20%). The epithelial displaying enteric adenocarcinoma-like morphology was focally positive for CDX2 in the third patient.

Gene mutation spectrum was depicted in Fig. 5. In three tumors, epithelial and mesenchymal retained highly coincident genetic abnormalities which involved 3 groups of genes (FAT3/LRP1B/PTCH1/RB1 in patient one, RB1/GRIN2A/FBXW7/EGFR/LATS2/PARP4/CDK8 /SDHA/TERT in patient two and KRAS/BRAF/STAT3/KMT2D/CDKN2A/CDKN2B in patient three). In patient one, epithelial component harbored missense mutation of CTNNB1 and was consistent with immunohistochemistry of aberrant nuclear localization of β-catenin in squamoid morule cells. DICER1, BCOR, PTPRT, CTCF and FAT1 mutations only presented in epithelial component. In patient two, BRCA2 mutation was found only in epithelial, while ALK, RICTOR, IL7R, DNMT3A, ASXL2, MYCN and CREBBP mutations were found only in mesenchymal component. In patient three, KAT6A mutation was found only in epithelial, while APC mutation was detected only in mesenchymal component, Furthermore, driver gene mutations of KRAS and BRAF were detected in patient 3. RB1 mutations were found in the first two patients. Patient with L-FLAC component retained mostly missense mutations while patient with pure H-FLAC had various mutation types. Germline TP53 mutation was detected in patient two and somatic TP53 mutations were not detected in all three tumors.