ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 production can be missing. Thus, immunohistochemistry as well as molecular studies are necessary to make the right diagnosis. E-PS-22-039 Why does not ossification of posterior longitudinal ligament involve an upper part of the axis? T. Yamaguchi*, H. Imada *Dokkyo Medical Universiry Nikko Medical Center, Japan Background & objectives: Ossification of posterior longitudi- nal ligament (OPLL) can involve any parts of the ligament only except an upper part of the axis. To elucidate the reason why this part is not affected we examined 52 cervical spines dissected at autopsy. Methods: The specimens were dissected from cadavers aged over 50 years old at autopsy performed in Dokkyo Medical University and Koshigaya Hospital. There were 39 men and 13 women with a mean age of 69 years old. The formalin fixed specimens were cut into sagittal slices with 5 mm in thick. Decalcified ones were processed for histology after X-ray examination. Results: OPLL were observed in 25 cases on X-ray. The most common type was segmental and the largest lesion involved con- secutive 3 vertebral bodies (C4-C6). The most common location was C6 in 20 cases followed by C4 and C5 in 13 cases, each, C7 in 12 cases, C3 in 5 cases, and C2 in 2 cases. OPLL was found along the axis but never seen at an upper half part. Seven OPLL lesions at intervertebral disc were found in 6 cases: C3/4 in one case, C4/5 in 3 cases, C5/6 in 2 case, and C6/7 in one case. In addition, a specific anatomical structure was found around the axis. Conclusion: Pathogenesis of OPLL is unknown, however, ligament ossification requires blood flow. This study demonstrated that the cervical longitudinal ligament except an upper part is directly attached to the posterior aspect of the cervical vertebral bodies and intervertebral discs. The upper part of the ligament is separated from the upper half of the axis because a bursa and the transverse ligament of atlas lay between them. We conclude that this anatomic structure does not lead to ligament ossification. E-PS-22-040 NTRK-rearranged spindle cell neoplasm: a case report S. Yilmaz Erozbek*, A. Cakir, S. Dervisoglu *Istanbul Medipol University, Pathology Department, Turkey Background & objectives: NTRK (neurotrophic tyrosine receptor kinase)-rearranged spindle cell neoplasms, included in the 5th edition of the World Health Organization (WHO) classification of Soft Tissue and Bone Sarcomas, are characterized by morphological and molecular features resembling lipofibromatosis-like neural tumours. Methods: A 2-year-old boy presented with painless mass that grew as the child got older was observed in the dorsum of the left hand. In the ultrasonographic examination, a vascularized fat-rich lesion measuring 45x16x40 mm was observed in the subcutaneous soft tissue. Excision of the lesion was performed. Prepared slides and blocks were presented to us for consultation. Results: No macroscopic information was available. Histologically, sections showed cellular spindle cell proliferation altered with adipose tissue, with pigmentation. In cellular areas, spindle cells showed moderate pleomorphism, ovoid-to-elongated nuclei with amphophilic cytoplasm. 7 mitoses/mm2 were counted. No necrosis was observed. Histochemical examination of pigmentation showed a positive reaction with Masson Fontana, compatible with melanin. Immunohistochemically, tumour cells were positive for panTRK, patchy positive for CD34, weak positive in myofibroblastic pattern for SMA, negative for desmin, EMA, HMB45, SOX-10. Ki-67 was 25%. We concluded that, this melanin pigment containing tumour similar to lipofibromatosis, is a NTRK-rearranged spindle cell neoplasm with low- intermediate histological grade. Investigation of NTRK fusion with molecular methods were recommended. Conclusion: The NTRK mutation is one of the new entities dis- covered in spindle cell neoplasms with genetic rearrangements. Although there is a wide histological presentation in the litera- ture, it is valuable to evaluate NTRK rearrangement in spindle cell neoplasms, especially when infantile fibrosarcoma, lipofi- bromatosis and fibrosarcoma-like morphology are observed. Molecular examination can be done, also pan-TRK İHC can be used to support the diagnosis. Demonstrating this genetic rear- rangement is clinically important for targeted therapies. E-PS-22-042 Case report of a primary renal vein leiomyosarcoma C. Karantzias, I. Nitsios, C. Roumbas, A. Dimitriadi, X. Gramma- toglou, C. Zorzos*, A. Kostopoulou, A. Kalantzi, E. Giagourta, G. Zografos, T. Choreftaki *Pathology Depar tment, General Hospital of Athens "G.Gennimatas", Greece Background & objectives: We report a rare case of leiomyosarcoma arising from the renal vein. Leiomyosarcomas are rare malignant soft tissue tumours. A minority of these originate from vessel walls, usu- ally from the vena cava with only few arising from other large veins. Methods: An 82 year old female with a history of malignant melanoma, presented at the hospital with a mass on the upper left abdominal quadrant diagnosed from a routine ultrasound. A CT and MRI were performed and a circumscribed large non-functioning mass at the location of the left adrenal gland and the retroaortic position of the left renal vein were depicted. Results: Histological examination revealed a tumour that consisted of intersecting fascicles of spindle-shaped cells with smooth muscle differentiation, nuclear pleomorphism and 10-19 mitoses per High Power Field (HPF). The neoplasm originated from the left renal vein, without invading the left kidney while pushing and causing atrophy to the left adrenal gland. Immunohistochemistry showed diffuse positivity for smooth muscle actin (SMA), Desmin, H-Caldesmon and negativity for S-100, Mart-1, HMB-45, SOX-10. Ki-67 was estimated 35%. Conclusion: These observations confirmed the diagnosis of a leiomyosarcoma of intermediate malignancy Grade 2 according to FNCLCC classification originating from the left renal vein. Primary renal vein leiomyosarcomas are quite rare with only a few cases reported in literature. E-PS-23 | E-Posters Thymic and Mediastinal Pathology E-PS-23-001 Mediastinal teratoma with 4 different somatic type malignan- cies: a case report A. Kotopoulis, P. Tziakou, A. Georgiou, D. Karagianni, G. Agrogiannis* *1st Department of Pathology, School of Medicine, National and Kapodistrian University of Athens, Greece S347