ECP 2023 Abstracts

S258 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Results: A 67-year old woman attended the colposcopy clinic with a history of persistent high-risk HPV infection and repeated LLETZ (large loop excision of the transformation zone) procedures for HSIL/ CIN3. In 2022 she underwent total abdominal hysterectomy as defini- tive treatment for residual disease of the cervix. Histological examina- tion of the cervix revealed residual HSIL/CIN3 with extensive endocer- vical gland colonisation. There was also involvement of the lower uterine segment and the endo- metrial cavity by strips and nests of dysplastic squamous epithelium. No true invasion was identified and following consultation with spe- cialist colleagues, it was agreed that the lesion was best classified as in situ i.e., HSIL/CIN3 replacing the endometrium. Conclusion: High grade squamous intraepithelial lesion (HSIL) of the cervix extending into and replacing the endometrium is a rare phe- nomenon, and potential diagnostic pitfall, with only occasional case reports. These lesions are best classified as in situ and do not show true evidence of invasion. Thorough sampling and microscopic examination for evidence of invasive disease is critically important in such cases. E-PS-10-024 Uterine inflammatory myofibroblastic tumour with FN1::ROS1 gene fusion: a tumour to be known C. Genestie*, S. Cotteret, M.A. Bani, J. Scoazec, N.I. Ben Romdhane *Department of medical biology and pathology, Morphological pathol- ogy laboratory, Gustave Roussy Cancer Campus, Villejuif, France Background & objectives: Most uterine inflammatory myofibroblastic tumours (IMTs) harbour ALK rearrangement. However, other gene alterations have been described. Herein, we report a case of a uter- ine IMT with FN1-ROS1 fusion and emphasize on the importance of extensive molecular testing in ALK-negative tumours. Methods: A 34-year-old woman presented with menorrhagia. Endo- scopic exploration found a well-circumscribed 35 mm intra-uterine lesion. The tumour was made of spindled to epithelioid cells in a myxoid stroma. A patchy expression of actin and desmin was noted. ALK was negative. Therefore, myxoid leiomyosarcoma was initially suspected. We received the specimen for second opinion, complemen- tary immunochemistry and molecular techniques. Results: Histologically, the tumour had suggestive morphologic fea- tures. It was made of bland spindle cells with hypercellular (fascicular/ storiform) and myxoid hypocellular areas admixed with scattered lym- phoplasmacytic infiltration. There was no atypia or increased mitotic figures. Tumour cells were weakly positive to actin and desmin. There was no expression of keratins, PS100, CD10, CD34 and ALK (ALK1 and D5F3 clones). No ALK-rearrangement was detected by fluorescen- cein situ hybridization. Interestingly, moderate and patchy cytoplasmic immunostaining for ROS1 was only noted. Targeted RNA sequencing revealed FN1-ROS1 rearrangement that fused FN1 exon 23 to ROS1 exon 34. We concluded to a IMT with a FN1::ROS1 fusion. Conclusion: This case highlights the importance of testing for non-ALK genes in ALK-negative uterine neoplasms morphologically compatible with IMT. The absence of ALK positivity in a lesion morphologically sug- gestive of IMT must prompt an extensive profiling combining immunohis- tochemistry, fluorescence in situ hybridization and especially RNA fusion analysis. Making an accurate diagnosis is essential since such patients may benefit from targeted therapy with tyrosine kinase receptor inhibitors. E-PS-10-025 Aggressive angiomyxoma mimicking a cervical polyp: uncommon presentation of a rare entity T. Georgescu*, A. Georgescu, D. Cretoiu, T.G. Jaswal, M. Sajin, N. Suciu *Department of Pathology, "Carol Davila" University of Medicine and Pharmacy Bucharest, Department of Pathology, National Institute for Mother and Child Health "Alessandrescu-Rusescu", Romania Background & objectives: Aggressive angiomyxoma of the female genital tract is a benign, slow-growing, spindle cell neoplasm, usually encountered in perineum and vulva of reproductive age women. Cervi- cal presentation is exceedingly rare, with only few case reports, and may pose difficult differential diagnoses. Methods: We report the case of a 41–year-old female, who presented to our outpatient Gynaecology Department for dysuria and abdominal pain. Upon routine speculum checkup, a large polypoid mass (32/12/8 mm), tan-coloured, with wide base, apparently originating from the external cervical os. The lesion was subsequently electroresected under general anaesthesia and sent to the Pathology Department for histo- pathological examination. Results: Histopathological examination revealed an incompletely excised polypoid lesion, covered by squamous epithelium and com- posed of bland spindle cells embedded in a loose myxoid stroma, with prominent capillary network. The differential diagnosis included a traumatized/oedematous cervical polyp, superficial angiomyxoma, deep angiomyxoma and myxoid liposarcoma. While the base of the tumour and the infiltrative character of the lesion could not be evalu- ated, immunohistochemical stains proved unequivocal. The lesion was diffusely positive for SMA, Desmin, CD34 and hormonal receptors (ER, PR), with a low Ki67 proliferation rate, confirming the diagnosis of aggressive angiomyxoma. The patient underwent a second interven- tion for complete excision and shows no signs of recurrence at 8-month follow-up. Conclusion: In conclusion, aggressive angiomyxoma of the cervix, although benign, is an extremely rare entity, with important clinical outcome due to its prognosis and evolution. Aggressive angiomyxoma of the lower female genital tract should be entirely excised in order to minimize the recurrence rate. Although no distant metastases have been reported, local infiltrative character and characteristic immuno- histochemical profile distinguishes aggressive/deep angiomyxoma from a superficial angiomyxoma or from a traumatized/ulcerated cervical polyp. E-PS-10-026 Mesonephric-like adenocarcinoma of the ovary - an underdiag- nosed entity T. Georgescu*, A. Georgescu, A. Cernat-Stefan, M. Sajin, N. Suciu *Department of Pathology, "Carol Davila" University of Medicine and Pharmacy Bucharest, Department of Pathology, National Institute for Mother and Child Health "Alessandrescu-Rusescu", Romania Background & objectives: Mesonephric adenocarcinoma is a rare aggressive tumour affecting the uterine cervix or corpus. In the cervix, it develops from mesonephric remnants, which may be present deep in the cervical wall and is composed of well-differentiated glands featur- ing eosinophilic intraluminal secretions. Methods: A 56-years-old female presented to our Gynaecological Department with abdominal pain. Ultrasound examination revealed a 12/8,5/7 cm solid left adnexal mass with variable echogenic areas. During surgery, the tan-grey tumour with multiple areas of necrosis was diagnosed as well-differentiated adenocarcinoma NOS on frozen section. Paraffin-embedded sections were supplemented by additional immunohistochemical stains in order to establish the final diagnosis. Results: Histopathological examination revealed a solid prolifera- tion of well-differentiated glandular structures with clear or pale- eosinophilic cytoplasm, elongated nuclei and intraluminal secretory material. The overall aspect was that of a well-differentiated endo- metrioid neoplasm without squamous differentiation and with rather frequent areas of necrosis. The tumour was diffusely positive for CK7, showed “wild-type” pattern of staining for p53 and was negative for hormone receptors as well as WT1 and p16. Additional stains showed diffuse positivity for PAX8, GATA3 and TTF1. Moreover, CD10 showed apical membranous positivity in most tumour cells and Ki67