ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 negative for EMA, SSTR2a, CD34 and STAT6. The biopsy of the lung nodules showed the same morphological and immuno- histochemical profile, leading to the diagnosis of intracranial SEF and metastatic relapse of disease. Molecular study by RNA sequencing was inconclusive due to poor RNA quality. Break-apart FISH for EWSR1 fusions was negative. Literature review showed only three intracranial sclerosing epithelioid fibrosarcomas. Metastasis of SEF occur in up to 50% of cases, most commonly to the lung. Conclusion: Diagnosis of extra-axial intracranial tumours can be quite challenging. Meningioma is the most common neoplasm but it may display a wide variety of patterns, making mesenchy- mal neoplasms, besides solitary fibrous tumour, an important differential diagnosis in selected cases. SEF usually harbours EWSR1/FUS-CREB gene fusions, nonetheless cases without this molecular alteration have been reported. Furthermore, an alter- native YAP1-KMT2A gene fusion has recently been identified. Accurate diagnosis is of utmost importance given its aggressive behaviour with frequent recurrences and late metastasis. E-PS-22-030 A case report of retiform hemangioendothelioma as pleural tumour with rib infiltration T. Pikivaca*, A. Lukac, A. Mataic, S. Seiwerth *University Hospital Centre Zagreb, Croatia Background & objectives: Retiform hemangioendothelioma is an extremely rare vascular tumour of intermediate biological behav- iour which is prone to local recurrence but rarely shows distant metastases. It predominantly arises in the skin and subcutaneous adipose tissue of the distal extremities. Methods: 39-year-old woman underwent video-assisted thoraco- scopic surgery during which a tumour of the left parietal pleura has been resected with partial resection of the seventh rib. The pleural tumour was radiologically detected during workup of an invasive breast cancer, earlier that year. (Neoadjuvant chemotherapy, left- sided mastectomy with axillary dissection and adjuvant chemo- therapy were performed). Results: Histologically, the resected pleural tumour showed reti- form arborizing vascular spaces lined by bland endothelial cells with hobnail nuclei, characteristic of retiform hemangioendothe- lioma. Immunohistochemical markers CD31, CD34 and ERG were positive, while D2-40, synaptophisin and HHV-8 were negative. Features of malignancy or any other type of vascular tumour were not present in this material, but the tumour infiltrated the underly- ing resected bone superficially and was on the resection margins marked with tissue dye. Given the possible local aggressive behav- iour and recurrence (60% of cases), additional resection and regular monitoring of the patient was recommended. Conclusion: Although retiform hemangioendotelioma predomi- nantly affects skin and subcutis, unusually affected sites (only few cases) are head and neck region, thorax, penis and pleura. Retiform hemangioendothelioma on location other than skin or subcutis may lead to corresponding symptoms or even threatened survival. It is important to completely rule out a possibility of more aggressive vascular tumours (e.g. angiosarcoma), which may harbour areas morphologically similar to retiform hemangioendothelioma. Reti- form hemangioendothelioma often recurs many years after diag- nosis so extensive local excision is required. E-PS-22-031 De-differentiated liposarcomas with heterologous and homolo- gous elements: MDM2, CDK4 and DDIT3 testing on several blocks with homologous and heterologous elements is useful for diagnosis D. Proca*, A. Lazim, J.J. Fu, I. Akhtar *Temple University, USA Background & objectives: Osteosarcoma (OS) heterologous compo- nent in dedifferentiated liposarcoma (DDL) is rare but should be con- sidered and MDM2/ CDK-4 testing employed. Myxoid liposarcoma- like (ML) homologous differentiation with simultaneous MDM2 and DDDIT3 amplification is also unusual and needs to be recognized. Methods: We report three special cases of DDL, two in the retrop- eritoneum and one in the abdomen: a DDL with OS differentiation, confirmed by MDM2 and CDK4 positive testing, as well as two DDL with homologous ML differentiation confirmed by simultane- ous positive MDM2 and DDIT3 testing. Results: The DDL with heterologous osseous differentiation and very rare WDL foci, which were important to identify in order to exclude the diagnosis of extraosseous OS. Without the rare foci of WDL, the extensive high grade spindled DDL may have been misinterpreted as part of an extraosseous OS. MDM2 and CDK4 testing was needed to guide the diagnosis. The other two cases are DDL with homologous myxoid differentiation; FISH testing for MDM2 and DDIT3 amplification is necessary. WDL and DDL can contain ML component, a diagnostic challenge when confronted with a small biopsy. Such tumours have been shown to contain co-amplifications of MDM2 and DDIT3, further adding to a diagnostic dilemma. Conclusion: The presence of pleomorphic cells or lipoblasts in WDL or DDL, as seen in our two cases, should prompt consider- ing MDM2 FISH testing in conjunction with DDIT3, rather than DDIT3 alone. Furthermore, the first case illustrates the utility of MDM2 and CDK4 testing in ruling out other high-grade sarcomas when a DDL diagnosis is uncertain due to absent WDL or presence of heterologous component, particularly high grade OS. E-PS-22-032 Multiple enchondromatosis of the upper limb in combination with multiple haemangiomas in a 20-year-old patient with Maf- fuci syndrome M. Mnikhovich, D. Kushch, A. Romanov*, T. Bezuglova *Central pathology laboratory, Research Institute of Human Mor- phology, Russia Background & objectives: Maffucci syndrome (MS) is a rare congeni- tal disease caused by mutations in the IDH1 or IDH2 genes, manifested by a combination of soft tissue haemangiomas with multiple enchon- dromes as well with other malignant soft tissue and bones tumours. Methods: We present a case of MS in a 20-year-old female with enchondromatosis of the upper extremities in combination with multiple haemangiomas of the face and oropharynx. The patient was operated on for the thumb of the right hand. MSCT showed solid septated mass with low echogenicity. Methods of histologic examination and IHC studies were applied. Results: Microscopy shows fragments of cartilage tissue in its own capsule, which has the structure of an enchondroma, with areas of myxoid degeneration of cartilage and severe necrobiotic changes; fragments of bone tissue with sclerotic changes, foci of axillary bone resorption and the growth of fibroreticular tissue in the intervertebral spaces. Against this background, there are multiple, merging foci of haemorrhages, as well as signs of patho- logical regeneration in the form of an excessive number of small, thin-walled blood vessels of the microcirculatory bed (mimicking capillary haemangioma). S344