ECP 2023 Abstracts

S345 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Methods: We present a rare case of non-small cell lung carcinoma (NSCLC) with an uncommon histopathological subtype and occurring at a relatively young age in this study. A 37-year-old female with a two- month persistent cough presented to the hospital. Imaging revealed a 40x35 mm mass in the right lung’s lower lobe. The resected specimen exhibited squamous and adenoid areas with intracytoplasmic mucin. Results: Immunohistochemistry revealed positive expression of TTF1, p40, CK7, and Napsin A in all cells, ruling out the diagnoses of aden- osquamous carcinoma and primary pulmonary mucoepidermoid carci- noma. Based on the literature search, the case was classified as "NSCLC, showing biphenotypic features," and was found to be PD-L1 positive. Visceral pleural invasion and six metastatic lymph nodes were also identified, resulting in a stage 2A diagnosis. Next-generation sequencing detected somatic mutations in the FGFR3 and RB1 genes. The patient received four cycles of navelbine-cisplatin chemotherapy and is currently under observation for 15 months without medication. No signs of recur- rence or metastasis have been detected in the latest control tomography. Conclusion: The significance of coexpression of TTF-1 and p40 in NSCLC cells remains unclear. To date, only 19 cases have been reported, which frequently present with advanced age at presentation. In most cases, TP53 gene mutation and FGFR1 amplification have been observed. However, our case differs from others reported in the literature due to its early onset and somatic mutations in FGFR3 and RB1 genes. E-PS-21-029 Seromucinous hamartoma mimicking lung cancer: case report F. Mundim*, R. Grande, M. Engelman, G. Engelman, P. Mundim, N. Sousa, E. Berti, M.C. Oliveira, G.H. Junqueira, G. Mendonça, A. Silva *UNIFENAS, Brazil Background & objectives: The patient is a 63-year-old man with previous surgery for colorectal adenocarcinoma without loss of DNA repair gene protein expression. CT scan of the chest reveals a vegetating lesion in the left main bronchus, suspicious for a lung tumour. Methods: Resection of the bronchial tumour was performed by endos- copy and the sample was sent for histopathological analysis. Results: Under microscopy, tumour tissue is composed of epithelial and mesenchymal components. The epithelial components are primar- ily seromucous acini similar to the salivary glands and the glands lining the respiratory epithelium. The mesenchymal components are consist- ent fibrous stroma, free of fat, smooth muscle and cartilage component, without cellular atypias. Immunohistochemistry was focally positive for epithelial membrane antigen (EMA) and tumour suppressor gene TP53 - p53, positive for cytokeratin CK7, and positive for less than 1% of Ki-67 cells of interest. Diagnosis confirmed by immunohistochemi- cal study: Seromucinous hamartoma. Conclusion: Seromucinous hamartoma that occurs in the lung is very rare and has unique clinicopathological features that need to be dif- ferentiated from other benign and malignant lung tumours, which can mimic lung cancer. E-PS-21-030 Primary adenoid cystic carcinoma of the lung: a case report M. Muñoz Martín*, M.L. Vazquez, S. Simón Alonso, M.C. Soriano Rodriguez, V. Sotelo Peña *Hospital Universitario Virgen de la Luz, Spain Background & objectives: Primary adenoid cystic carcinoma of the lung (ACC) is a low-grade malignant epithelial neoplasm, originates in trachea and bronchial system, without association with cigarette smoking and represents 0.04-0.2% of all lung cancers, therefore clin- icopathological behaviour is poorly understood nowadays. Methods: We have reviewed 50 cases per year of primary lung carci- noma during the last twenty years, which only one was diagnosed as a ACC (1/1000). We present one case of ACC, and analyse its evolution and characteristics in relation to features described up to now in the context of this entity. Results: The patient was a 42-year-old man, former smoker, and with recurrent pneumonia for one year. Fiberoptic bronchoscopy described an infiltrating lesion in traqueal carina. Endobronchial resection of the lesion was performed. Histologically, the tumour presented a cribriform pattern, pseudocystic spaces containing basement membrane-like material, lined by a luminal cuboidal line of cells and a peripheral myoepithelial cells. Immunohis- tochemistry: positive for Vimentin, smooth muscle actin, S100 and p63. Five years later, he presented an unresectable recurrence of lesion, receiv- ing radiotherapy and several lines of chemotherapy depending on the evolution of size of lesion. Currently, the patient is still alive and on active maintenance treatment with pemetrexed with stabilization of disease. Conclusion: ACC has a prolonged clinical course, with high recur- rence trend. The stage at diagnosis, positive margins, and solid pattern are indicators of a poor prognosis. Studies should have a long follow-up due to low frequency and long survival of this type of tumours, as in the case of our patient. E-PS-21-031 Thoracic SMARCA4-deficient undifferentiated tumour with ana- plastic lymphoma kinase (ALK) rearrangement - a case report J.H. Nam*, Y. Choi *Chonnam National University Hospital, Republic of Korea Background & objectives: Thoracic SMARCA4-deficient undif- ferentiated tumour (SMARCA4-DUT) is a recently identified high- grade malignancy. It is characterized by inactivating mutations of SMARCA4, gene encoding the ATPase subunit of the SWI/SNF chromatin remodelling complexes. We report the case of thoracic SMARCA4-DUT with ALK rearrangement. Methods: A 59 years old male visited the hospital complaining of 1-month history of chest pain. He was 30-pack year Ex-smoker and had no comorbidity. Chest radiograph and computed tomography showed a 13 x 7.8 cm sized heterogenously enhancing mass involving right mid- dle lobe and extending to adjacent lobes. He was performed lobectomy with stage IIIA (pT4N0M0) malignancy. Results: The resected specimen showed a poorly differentiated malignant neoplasm, characterized by sheets of epithelioid cells with moderate amounts of eosinophilic cytoplasm, atypical vesic- ular nuclei and focal necrosis. Some of the cells have rhabdoid morphology. Immunohistochemistry showed that the neoplastic cells were entirely negative for SMARCA4, indicating loss of the product of this gene in the SWI/SNF complex. There was positive in situ hybridization for ALK gene, and next generation sequenc- ing revealed the ALK rearrangements with intergenic-breakpoints. The patient had been received an adjuvant chemotherapy to prevent postoperative recurrence. But, about 2.8 cm sized mass, near opera- tion stump site, was shown. At present, three cycles of ALK-tyrosine kinase inhibitor are being treated. Conclusion: Our case highlights the significance of ALK rearrange- ment identification in the quest for the precise therapeutic potential of thoracic SMARCA4-DUT. Given the rarity of this condition and the lack of relevant literature, further studies are still needed. E-PS-21-032 Blastomatoid pulmonary carcinosarcoma - a case report and lit- erature review J.H. Nam*, Y. Choi *Chonnam National University Hospital, Republic of Korea Background & objectives: Blastomatoid pulmonary carcinosarcoma is one of the rarest histologic types of carcinosarcoma of the lung.