ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Conclusion: Although the presence of implanted foreign materials such as: Dacron and plastic grafts, steel plate and bone wax, retained for prolonged periods is known to be very rarely in association with the development of angiosarcomas, there are no cases reported in the literature regarding the association with retained surgical gauzes. Like all the abdominal textilomas, a highly aggressive cancer arising around a retained surgical gauze is a serious medico-legal problem leading to a poor prognosis and a high mortality rate. E-PS-22-006 Malignant solitary fibrous tumour of the mandibula: a case report S. Ben Cheikh*, A. Baccouche, M. Krifa, S. Mestiri, W. Majdoub, A. Bdioui, S. Hmissa *Pathology department, Sahloul University Hospital of Sousse, Tunisia Background & objectives: Solitary fibrous tumour (SFT) is a rare neoplasm arising most commonly in the thoracic cavity. Those occur- ring in the head and neck represent 10% of all cases. We report a case of malignant SFT of the mandibula with literature review. Methods: We report a case of a 73-year-old man, presented with a history of swelling in his lower jaw for the past six months. On examination, the mass was painless, nodular, measuring 1,5cm in great dimension and expanding to the soft palate. The computed tomography scan revealed a destructive soft tissue mass. The patient underwent a surgical resection. Results: Macroscopically, the mass was firm, lobulated and gray- white in colour with haemorrhage. Microscopically, the tumour consisted of spindle cells arranged in long, interlacing fascicles and whorls. The cells showed moderate atypia. The mitotic range was 6 mitoses / 10 high power fields. The cells grew around dilated, branched thin walled vessels. The surgical margins were positive. Immunohistochemically, tumour cells stained positive for CD34 and STAT6. They were negative for PS-100, β-catenin, Erg, smooth-muscle actin and desmin. Based on these histological and immunopathological findings, the diagnosis of malignant solitary fibrous tumour of the mandibula was made. Conclusion: The diagnosis of malignant solitary fibrous tumour of the mandibula might be challenging for pathologists. Awareness of it’s occurrence in this atypical site is crucial in order to prevent confusion with other spindle cells neoplasms. E-PS-22-007 Osteosarcoma of the bone in patient with primary hyperparathyroidism S. Ben Cheikh*, A. Bdioui, S. Moussa, O. Belkacem, W. Majdoub, A. Baccouche, S. Hmissa *Pathology Department, Sahloul University Hospital of Sousse, Tunisia Background & objectives: The association between osteosarcoma and hyperparathyroidism is very rare, only 10 cases have been reported in the literature to our knowledge. Herein we report an uncommon case of osteosarcoma in women with primary hyperparathyroidism. Methods: A 39-year-old female presented to our hospital for a subtrochanteric femoral fracture through a lytic lesion. She underwent resection of the bone lesion and the fracture was immobilised. The surgical specimen was analysed in the department of pathology. Results: The pathological examination showed an undifferentiated tumour composed of pleomorphic, epithelioid and spindle cells producing osteoid matrix in a lace-like arrangement. The diagnosis of high-grade osteoblastic osteosarcoma was made. Afterwards, she was referred to an oncologist for chemotherapy. In the meantime, she experienced a remarkable remission of left hip pain. A computed tomography scan was performed and showed osteolytic lesions of left hip and L5 vertebra. Therefore, the patient was managed by an endocrinologist who discovered primary hyperparathyroidism with an elevated serum calcium and parathyroid hormone. Conclusion: The patient in the present report provides one more clinicopathological example of an osteosarcoma in association with hyperparathyroidism. In light of the increased use of parathormone for treating osteoporosis, we should be aware of possible coexistence between these two conditions. E-PS-22-009 Anastomosing haemangioma: report of 3 cases with molecular and immunohistochemical studies Y. Chang Chien*, A. Mokánszki, L. Beke, G. Méhes *Dept. of Pathology, University of Debrecen, Clinical Center, Hungary Background & objectives: Anastomosing haemangioma (AH) is a newly described distinct vascular neoplasm that, histologically, may confuse with well-differentiated angiosarcoma (AS) for those who are unfamiliar with this rare entity. Methods: We aimed to identify the molecular genetic differences between AHs and ASs by carrying out immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and next- generation sequencing (NGS) analysis from three AHs and three ASs Results: Immunohistochemically, all six cases showed positivity for cyclin D1 and pERK. The three AH case results were weakly positive for p53 and MIB-1, whereas the IHCs for HIF-1α were negative in all three cases. Those three cases of angiosarcoma revealed strong, diffuse positivity for p53, 50-70% for MIB-1, and multifocal, moderate-to-strong HIF-1α expression. To further clarify the difference of p53 expression, we carried out a FISH which revealed polysomy in all three AS cases; genetic aberration was absent in the AH group. In one AH case, the GNA11 c.627G>T; p.Q209H nucleotide variant was detected. Conclusion: We demonstrated three cases of anastomosing haemangiomas with one case harbouring a GNA11 mutation which, besides conforming to its clonal nature, also serves as an impor tant molecular signature to distinguish AHs from well-dif ferentiated ASs. We also addressed t he potential molecular differences between these two entities. Nevertheless, due to the small sample size and its rarity, a larger scale study is needed to elucidate this issue. Clinical information and histology features still serve as the gold standard for the correct diagnosis. E-PS-22-010 MKL2 rearranged chondroid lipoma - a pitfall in frozen section interpretation Z.S. Chua*, S.W. Leong, Y. Soon, B. Wu, C.H. Kuick, K.T. Chang, Y. Mok *National University Health System, Singapore Background & objectives: Chondroid lipomas are rare benign adipocytic tumours that can be mistaken for more aggressive S337