ECP 2023 Abstracts

S98 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 immunoreactivity, accepted as the gold standard for diagnosis, was detected in all cases. 3 of the 12 cases (25%) had lymph node metastasis at the initial diagnosis. In follow-up, lung metastasis was detected in 4 cases (33%). Conclusion: LGFS is a rare sarcoma with local recurrence and metas- tasis risk although it reveals bland morphology. It can result in differ- ential diagnosis problems with other fibroblastic tumours. PS-14-002 Importance of transthyretin-derived amyloidosis (ATTR) detection in carpal tunnel syndrome (CTS) C. Girleanu*, J. Bissonnette, P. Fleming, N. Bermingham, L. Burke *Department of Pathology, Cork University Hospital, Cork, Ireland Background & objectives: Transthyretin-derived amyloidosis (ATTR) is a rare progressive multisystemic disease. Advancements in therapy warrant attention to its indentification. Carpal tunnel syndrome (CTS) is a known symptom manifestation. An institutional audit was per- formed to evaluate the detection of ATTR in CTS cases. Methods: A COGNOS database search of CTS samples containing amyloid at the Pathology Department. CUH from 2008 to 2022 was performed. Data analysed for these cases included age, gender, locali- zation of amyloid deposits (confirmed by Congo Red stain) within the tissue, and results of Amyloid sub-type classification performed at the National Amyloidosis Centre, UK. Results: 126 cases of CTS were identified over a 14-year period (2008-2022). 21 cases displayed amyloid appropriate birefringence on Congo Red analysis with an average age of 75 years (age range- 57 to 91 years). There was a slight excess in males (11/21). In 20 cases amyloid deposits were identified within the stroma with only one case having a known Monoclonal IgM Kappa Band paraprotein. One case incorporated amyloid deposits in both the stroma and vessels. In the 11 cases subtyped, including the case with a known paraprotein, all contained transthyretin (TTR) amyloid subtype. Conclusion: Given the therapeutic advances in management of ATTR amyloid and its known associations with other disease processes such as cardiomyopathy, neurological disorders, etc., its detection is very impor- tant. Our results indicate that all samples of CTS with positive Congo Red amyloid deposits could act as an early histological diagnosis for this entity and therefore subtype analysis should be performed on all cases. PS-14-004 Osteosarcoma of the toe: a clinicopathologic study of 4 cases O. Houghton*, V. Sumathi, A. Rosenberg *Royal Group of Hospitals, Belfast, Ireland Background & objectives: Osteosarcoma of the toe is extremely rare with only 10 well described cases in the literature. It is often unexpected clinically and radiologically, and the histological diagnosis may be challenging. We describe the clinicopathologic features of four cases. Methods: The consultation files of one of the authors and the sur- gical pathology files of the Department of Musculo-Skeletal Pathol- ogy, Royal Orthopaedic Hospital, Birmingham, were searched for toe osteosarcoma. Available H&E slides on each case were retrieved and reviewed. Radiographs were available for review in 1 case. Relevant clinical information was obtained by written questionnaires with refer- ring pathologists and treating physicians. Results: The patients included 3 males and 1 female, ranging in age from 15 to 54 (mean age 32). The tumours arose in the proximal pha- langes, occurring in the first, third and fifth toe, respectively. The spe- cific phalanx of origin in one case was not known. One tumour was a parosteal osteosarcoma and 3 were intramedullary osteosarcomas. The intramedullary tumours included a conventional low-grade central osteosarcoma, an osteoblastoma-like osteosarcoma and a conventional high-grade osteosarcoma. Of the two patients with known follow-up data (the parosteal osteosarcoma and the osteoblastoma-like osteosar- coma) there was no evidence of recurrence or metastasis after a period of 84 months (range 21 to 147 months). Conclusion: This is the largest series of osteosarcoma of the toe. As osteo- sarcoma is often unexpected clinically and radiologically in this location and as low-grade osteosarcoma subtypes, which are more common in the toe, can be confused histologically with benign fibroosseous lesions or with the chondrosseous lesions which have a predilection for the toes, there is potential for diagnostic delay. Pathologists should be aware of osteo- sarcoma of the toe to ensure prompt diagnosis and appropriate treatment. PS-14-005 Prognostic and diagnostic significance of mitotic activity between low grade dedifferentiated liposarcoma and cellular well differenti- ated liposarcoma J. Lee*, H.J. Kwon, G. Choe, K.S. Lee *Seoul National University Bundang Hospital, Republic of Korea Background & objectives: Morphologically ambiguous lesions of overlap between well differentiated liposarcoma (WDL) and dediffer- entiated liposarcoma (DDL) are not infrequently encountered. Inter- pretative difficulties arise when the low-grade sarcoma component that does not meet the criteria for typical DDL. Methods: Tumours of this feature are considered to represent “low- grade (LG) DDL” or “cellular WDL”. Some studies suggested that at least 5 mitotic figures per 10 high-power fields (≥5/10 HPF) are required for diagnosis of DDL. In our study, liposarcoma contains LG sarcoma- tous lesion with mitotic count <5/10 HPF were considered as LG DDL. Results: A total of 244 patients with liposarcoma (average age=60, range=18-91years) were evaluated. The MDM2 amplification was determined using fluorescence in situ hybridization in all cases. The study included 46 (20.53%) typical DDL,28 (11.47%) LG DDL, and 170 (69.67%)WDL. Sixty-nine (28.27%) liposarcoma originated from the retroperitoneum and 175 (72.72%) were observed in limbs and trunk, etc. Kaplan–Meier analysis indicated that DDL was significantly associated with poor recurrence free survival compared (RFS) to WDL (P< 0.001).LG DDL was significantly correlated with a worse RFS compared to WDL (P=0.013). However, LG DDL was not correlated with a better RFS compared to typical DDL (P=0.704). Conclusion: We investigated the clinical relevance of mitotic activity in MDM2 amplified liposarcoma. There is a suggestion that liposar- coma with LG sarcoma component (mitotic count <5/10 HPF) should be included in the WDL or cellular WDL. However, LG DDL definitely shows poor RFS compare to WDL and does not significantly have a better RFS than typical DDL. Thus, LG DDL should not be underes- timated as cellular WDL. PS-14-006 Clear cell chondrosarcoma, an aggressive low grade chondroid neoplasm - a case series S. Naresh Shah*, A. Parameswaran *Apollo hospitals, India Background & objectives: Clear cell chondrosarcoma is a low grade chondroid neoplasm which constitutes 2-4% of conventional chondro- sarcomas and 0.4% of primary bone neoplasms. They radiologically mimic a benign lesion and therefore pathological examination is the gold standard for diagnosing this entity. Methods: We retrieved 109 chondrosarcomas from Apollo hospital lab- oratory database from 2012-2022, of which only 7 cases were of Clear cell chondrosarcoma. Histopathological examination was the mainstay of diagnosing this entity with immunohistochemistry when indicated.