ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 E-PS-09-030 Metastatic epithelioid trophoblastic tumour: a case report G. Martins Pereira*, M. Araújo, J. Ferreira *Instituto Português de Oncologia de Lisboa Francisco Gentil, Portugal Background & objectives: Epithelioid trophoblastic tumour (ETT) is a rare form of gestational trophoblastic tumour and 25% present with FIGO stage IV disease. We report a case of a patient with stage IV ETT expressing programmed cell death protein 1 (PD-L1). Methods: A 40-year-old woman presented with abnormal uter- ine bleeding and recent weight loss. An MRI revealed a 4.3cm endometrial tumour. On biopsy, a diagnosis of undifferentiated carcinoma was suggested. Hysterectomy with bilateral adnex- ectomy and omentectomy was performed. Pre-surgical β-HCG levels were not assessed and post-surgery β-HCG was 4.1mUI/ mL. Currently, 3 months after surgery, the patient is under adju- vant chemotherapy. Results: Gross examination revealed a white tumour invading the outer half of the myometrium and multiple small white nodules in the omentum. Histologically, the tumour showed a multinodu- lar proliferation of monotonous medium-sized eosinophilic cells, arranged in strands and nests, associated with extensive geo- graphic necrosis and deposits of hyaline-like material. The cells displayed eosinophilic/clear cytoplasm with round nuclei and small nucleoli. Neoplastic cells expressed keratins (AE1/AE3 and cam5.2), p63, GATA3, inhibin (focal), HPL (focal) and PD-L1 (>50%). The cells did not express SMA, desmin, β-HCG, PAX2 or PAX8. The proliferative index Ki-67 was 20%. A diagnosis of an epithelioid trophoblastic tumour with epiploic metastasis was rendered. Conclusion: Epithelioid trophoblastic tumours most often present in FIGO stage I/II and treatment is therefore surgical. In the rare event of advanced disease, conventional chemotherapy has a low success rate. Since ETT often shows strong PD-L1 expression, as seen in our case, a few case reports have showed a good clinical response to immune checkpoint inhibitors (such as pembrolizumab). Immunotherapy may prove useful in the treatment of metastatic drug-resistant ETT. E-PS-09-031 Histological particularities of pulmonary phyllodes tumour metastasis: a case report I. Msakni*, R. Aouadi, N. Mansouri, F. Gargouri, M. Ben Thayer, K. Tlili, B. Laabidi *Department of Pathology, Military Hospital of Tunis, Tunisia Background & objectives: Phyllodes tumours (PT) are rare neoplasms accounting for less than 1% of all breast cancers. Malignant phyllodes tumours are likely to metastasize mainly to lungs. We, hereby, present an uncommon histological pattern of lung metastasis of a Phyllodes tumour. Methods: We present a case of lung metastasis in a patient known to have a breast phyllode tumour. Results: A 40-year-old woman with history of left mastectomy for phyllodes tumour three years earlier presented with a rapidly growing mass of the right lung. Chest-Tomography Scan showed a tumour of the middle lobe along with pleural infiltration. A lobec- tomy was performed. Histological examination showed a mesen- chymal proliferation entrapping ductal structures that showed to be bronchic lumens expressing TTF1 and not a ductal tumoral com- ponent. The tumour cells were arranged in intersecting bundles. They had atypical spindle-shaped nuclei. Mitosis and mitonecro- sis figures were noted. The tumour was highly vascularized. The diagnosis of pulmonary and pleural metastasis of phyllodes tumour was established. Conclusion: PT are biphasic tumours composed of both stromal and an epithelial component. PT has an inherent recurrence and metastatic potential especially to the lung. Histologically, mesen- chymal component may be the only pattern observed in metastasis site. That could be challenging for the diagnosis especially if no history of breast cancer is known. E-PS-09-032 Uterin spindle cell mesenchymal neoplazm, NTRK fusion-pos- itive uterine sarcoma B. Konuk*, C.S. Topal *Umraniye EducationTraining Hospital, Turkey Background & objectives: Uterine sarcomas are a rare type of tumour with a wide range of morphological and genetic characteristics. Recent improvements in the genetic characterisation of these tumours have created a new clinicopathological category that includes NTRK-rear- ranged uterine sarcomas. Methods: In the hysterectomy material of a 52-year-old female patient with menorrhagia, a 5 cm diameter solid tumoral lesion was identified. When the histomorphological observations were combined with the immunohistochemical profile, the group of CD34,S100,Pan-Trk positive uterine spindle cell neoplasms was classified as NTRK fusion uterine sarcoma. The next generation of sequencing investigation found fusion between the NTRK1gene exon10 and the TPM3gene exon7 and junction regions. Results: These neoplasms have a variably cellular and fibrosar- coma-like appearance and are distinguished by generally homo- geneous spindle cells with a scant cytoplasm. Atypia is usually mild to moderate. Mitotic activity is varied. Differential diagnosis includes high-grade endometrial stromal sarcoma, undifferentiated uterine sarcoma, inflammatory myofibroblastic tumour, COL1A1- PDGFB fusion sarcoma, solitary fibrous tumour, adenosarcoma and malignant melanoma. In leiomyosarcoma-like uterine sarcomas that are desmin and h-caldesmon negative and lack ER and PR expression, if S100 and CD34 is positive, we recommend pan- Trk immunostaining and if it is positive then molecular studies to screen for NTRK fusion for differential diagnosis and treatment options. Conclusion: The importance of NTRK mutations in the devel- opment of numerous solid tumours is increasingly recognized. Accurate identification of these rare tumours is critical for the treatment option of TRK inhibitors like Larotrectinib that is a pan- TRK inhibitor. This case demonstrates the importance of consider- ing newly defined NTRK fusion sarcomas in the histopathological evaluation of uterine sarcomas in terms of diagnosis and treatment. E-PS-09-033 Benign cystic mesothelioma: a rare case report B. Konuk*, Ş. Çetin *Umraniye EducationTraining Hospital, Turkey Background & objectives: Benign cystic mesothelioma is a mesoder- mal tumour that covers the surface of organs such as the peritoneum, pleura, and pericardium. It is a proliferative neoplasm composed of mesothelium epithelial and mesenchymal cells. Methods: A 31-year-old female patient presented to the gynaecol- ogy outpatient clinic with inguinal pain. Ultrasonographic imaging revealed a 200*117 mm cystic tumour on the anterior abdominal wall. Total abdominal colectomy, low anterior resection, subtotal S264