ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 13%, 19% . The PGF including MYC was 14% in ALK-positive and 19% in triple-negative cases. Additionally, the TP63 -rearranged cases showed a strong gene fusion connection between FOXP1 and EIF4E3 . Conclusion: The ALK-negative ALCL is a rare lymphoma, which is now classified as a separate entity that should be differentiated from primary cutaneous ALCL, and other T-cell/B-cell lymphomas with CD30 expression and anaplastic morphology. Comprehensive molecular studies under a larger cohort of ALK- ALCL are limited due to the low number of cases. Further investigation is needed not only to give more insight into the clinical significance of genetic alterations but also in search of new molecular targets for person- alized therapy. PS-10 | Poster Session Soft Tissue and Bone Pathology PS-10-001 Diagnostic utility of h3.3k36m immunostaining in chondro- blastomas: a study of 16 cases from a tertiary cancer referral centre in India V. Dave*, B. Rekhi *Tata Memorial Hospital, India Background & objectives: Chondroblastoma is a relatively uncom- mon benign bone tumour. At times, there is a challenge in differentiat- ing it from its diagnostic mimics, especially on limited biopsies, with treatment-related implications. To evaluate H3.3K36M immunostaining in chondroblastomas. Methods: Ten cases were in the form of biopsy specimens and six were referred cases in form of paraffin blocks. Immunohistochemi- cal staining for H3.3K36M (monoclonal, RM193, 1:100 dilution) was graded in terms of staining intensity(1+to 3+) and the percent- age of tumour cells showing unequivocal nuclear staining. Proximal tibia (5/16, 31.25%) was the commonest site, followed by the proximal humerus (4/16, 25%). Results: We observed positive immunohistochemical staining for H3.3K36M in 15/16(93.75%) chondroblastomas, including all the tumour components, such as tumour cells and pink cartilage, but sparing the osteoclast-like giant cells. The percentage of tumour cells showing positivity ranged from 30% to 95%. We observed 3+ stain- ing in 13/15((86.6%) cases and 2+ staining pattern in 2/15(13.3%) cases. A single case, which showed nuclear atypia displayed positive immunostaining for H3.3K36M in 80% of tumour cells with 3+ stain- ing. None of the other 12 giant cell-rich lesions, including giant cell tumour of bone, displayed positive immunostaining for H3.3K36M. Conclusion: Overall diagnostic sensitivity of H3.3K36M for chon- droblastoma was 93.7% and specificity was 100%. This study, which is one of the first from our country, supports the diagnostic value of H3.3K36M for diagnosing chondroblastoma, including its distinction from its various diagnostic mimics on limited biopsy specimens. PS-10-003 Metalic-alloy wear debris after total hip arthroplasty is induc- ing periprosthetic tissue inflammation on subcellular level S. Fokter*, R. Podlipec, E. Punzón-Quijorna *University Medical Centre Maribor, Slovenia Background & objectives: The metallic-associated adverse local tissue reactions (ALTR) and events accompanying worn implant materials are poorly understood on the subcellular level. Current immunohistochemical techniques lack chemical sensitivity to investigate causal relations between material and biological response on submicron scale. Methods: A combination of photon, electron and ion beam micros- copy-spectroscopy techniques including hybrid optical fluorescence and reflectance micro-spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), helium ion microscopy (HIM) and micro-particle-induced X-ray emission (micro-PIXE) were applied on periprosthetic tissue obtained at revi- sion surgery of a patient with osteoarthritis, who was treated earlier with a titanium-alloy total hip arthroplasty. Results: Micron sized wear debris was found as the main cause of the tissue oxidative stress exhibited through lipopigments accumulation in the nearby lysosomes. This may explain the signs of chronic inflam- mation from prior histologic investigation. Furthermore, insights on extensive fretting and corrosion of the debris on nm scale and a quantitative measure of significant Al and V release into the tissue together with hydroxyapatite-like layer formation particularly bound to the regions with the highest Al content were revealed. Finally, by micro-PIXE we observed a wide spread of Ti- alloy debris throughout the whole tissue sample and confirmed selective metal leaching that corresponds to elevated concentrations in the patient’s serum. Conclusion: The functional and structural information obtained at the subcellular level contributes to a better understanding of the macroscopic inflammatory processes observed on the tissue level. The established label-free correlative microscopy approach can efficiently be adopted to study any other clinical cases related to ALTR, as it can reveal more insights into implant rejection pro- cesses compared to the conventional histological examination fur- ther down on a submicron to single molecular scale. Funding: This research was funded by Helmholtz European Part- nering (CROSSING project, Grant-No: PIE-0007) and the Euro- pean Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 799182 (TissueMaps project). PS-10-004 Extraadrenal soft-tissues Myelolipomas: clinicopathological study of 10 cases M. Garcia Martos*, Y. Gómez Navarro, C.M. Vieru, A. Panizo Santos *Hospital General Universitario Gregorio Marañón, Spain Background & objectives: Myelolipoma is an uncommon benign tumour. It is most often found in the adrenal glands, although lesions in other unusual sites have also been described. The aim of our study is to describe the clinicopathological features of extraadrenal myelolipomas. Methods: The pathology departmental archives of two University Hos- pitals were searched from 2005-2021 for patients originally diagnosed as extraadrenal myelolipoma. The cases were reviewed by the authors. Clinical parameters such as age, gender, tumour sites, and follow up were obtained from the existing medical records. Results: Ten patients were identified: 7 males and 3 females, age ranged from 55 to 48 years. None of the patients had a previous history of malignancy or haematological diseases. All patients were diagnosed incidentally. The tumours involved posterior mediastinum (1), retro- peritoneum (2), pelvic soft tissues (1), and paravertebral presacral (6). CT scan showed in all patients a well-demarcated tumour with fat density showing heterogeneous enhancement. So liposarcoma was suspected and surgical resection was performed. The tumours were well-circumscribed, encapsulated, with yellow to grey cut surfaces. Histologically, the tumours showed mature adipose tissue and hemat- opoietic elements, with concordant inmunohistochemistry. All patients went follow-up with no recurrence at the time of evaluation. S119