ECP 2023 Abstracts

S178 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Methods: A prospective cross-sectional analysis of 50 cases of salivary gland lesions was conducted in a period of 6 months in histopathology department. ROSE was performed and aspirated material was spread on slides and stained with diff quik stain. Lesions were then categorized as per Milan System. The Data was entered and analysed by using SPSS version 21. Results: A cross sectional study was conducted in histopathology labo- ratory with a sample size of 50 salivary gland lesions presenting in both indoor and outdoor patients. Most affected site was parotid gland fol- lowed by submandibular gland and minor salivary glands respectively. Majority of the challenges were faced in categorizing salivary gland lesions with suspicion of neoplasm on the basis of clinical and radio- logical data but the Milan category ’non-diagnostic’ was assigned either due to lesional heterogeneity, fibrosis or necrosis resulting in non-repre- sentative sampling, aspiration of only myxoid material lacking a cellular component and various preparation artifacts during staining procedure. Conclusion: Challenges faced during rapid onsite evaluation of sali- vary gland lesions can be minimized by using appropriate aspiration techniques, preservation of aspirated material for further evaluation and additional ancillary testing and provision of appropriate clinical and radiological data useful in deciding type of aspiration technique, nature and exact site of the lesion. Effective collaboration is needed between surgeon, radiologist, cytotechnicians and both resident and reporting pathologist in order to minimize wastage of time and resources and repeat testing. E-PS-04-015 Cytohistologic correlation of gynaecologic malignancies: can peri- toneal fluid cytology reliably subtype gynaecologic malignancies? T. Sabljic*, S.K. Lou *University Health Network, Canada Background & objectives: Cytological examination of peritoneal fluid (PTFL) often represents the first and only pathological speci- men available to guide management of gynaecological malignancies (GM). This study examines the cytohistologic concordance between subtyping of GM between PTFL and its subsequent surgical speci- men (SS). Methods: The study retrospectively identified positive PTFL speci- mens with a GM between 2017 and 2022. Cases where the PTFL was obtained after or concurrently with its diagnostic SS (biopsy/resection) were excluded. The diagnosis, including histotype and grading, was compared to its corresponding SS with an analysis of potential factors leading to its cytohistologic discordance. Results: GM affected 55.8% (502/899) of malignant PTFL, of which, 22.3% (112)/15.7% (79) was the initial/only diagnostic sample, respec- tively. Compared to SS, when subtype was rendered/favoured (95/112, 84.8%), PTFL cytology had an accuracy of 97.9%. Factors in lack of/ discordant subtyping include cytopathologist preference, specimen limitations, or discordance between morphology and immunohisto- chemistry. In six cases (5.4%), the PTFL diagnosis was more than or as definitive as the SpS diagnosis. In five cases (4.5%), cytology correctly identified one of the components of a mixed carcinoma/car- cinosarcoma. In the six cases where the initial SS was non-diagnostic due to lack of/scanty lesional tissue or necrosis, the subsequent PTFL was diagnostic. Conclusion: When compared to SS, diagnosis and subtyping of GM on PTFL cytology is highly accurate and sometimes, more definitive than its surgical counterpart. In some cases, subtyping is limited by extrinsic factors (e.g., specimen limitations, immunohistochemistry discordance with morphology). In other cases, cytopathologists prefer not to subtype despite classic morphologic and immunohistochemi- cal features. This highlighted an opportunity for improvement in the diagnosis/subtyping of GM in PTFL, which may be the initial or only diagnostic specimen prior to patient treatment. E-PS-04-016 Atypical pleural liquid cells reveal their secret B. Suciu*, A. Maggio, C. Laurent *Centre Hospitalier de Béziers, France Background & objectives: Primary effusion lymphoma is a rare vari- ant of diffuse large B-cell lymphoma which develops similarly to an effusion located inside the serous cavities. The purpose of this paper is to highlight the algorithm used to reach this difficult diagnosis. Methods: One Papanicolaou (PAP) stained slide, two May Grunwald- Giemsa (MGG) stained slides and a cell-block, standard staining, hematoxylin and eosin, were examined. A panel of immunohisto- chemistry markers was ordered; the slides were stained following the standard protocol. The markers used are: CD45, CD20, CD3, CD138, Ki-67, HHV8, MUM1, ALK, EBV-LMP1, CK AE1/AE3, Ber-Ep4, CK 5/6, WT1, Calretinin, SOX10. Results: The majority of markers came out negative: CK AE1/AE3, Ber-Ep4, CK 5/6, WT1, Calretinin, SOX10 with the exception of CD45. Ki67 80% - nuclear stain. Mesothelial tumours, carcinoma and melanoma are excluded. This did not conclude the case, so a second batch of immunohistochemistry markers was performed, with the results being quite a surprise: the cells were negative for CD20, CD3 and positive for CD138. Based on the plasmablastic morphology and the fact that the cells were CD20, CD3 negative and CD138 positive, a third round of immunostains is ordered, following a specific algorithm. The cells were HHV8, MUM1 positive and ALK, EBV-LMP1 negative. The diagnosis of primary effusion lymphoma was concluded. Conclusion: Primary effusion lymphoma is a rare form of large B-cell lymphoma which develops in the serous cavities in patients usually infected with HIV or immunocompromised by transplants. This case was challenging because of cell morphology, but also because the aeti- ology of the effusion was thought to be of cardiac or renal origin. The key histological aspects are moderate to large sized plasmablastic-like cells that are negative for B-cell markers CD20, CD79a, PAX 5 and are positive for CD138, CD45, MUM1 and HHV8. E-PS-04-017 Acantholytic squamous cell carcinoma mimicking epithelioid angiosarcoma: a diagnostic challenge by cytology M. Taweevisit*, P. Thorner *Department of Pathology, Thailand Background & objectives: Squamous cell carcinoma is the most com- mon malignancy of the head and neck region. Most cases present little diagnostic difficulty on fine needle aspiration (FNA), but unusual vari- ants can be problematic. Methods: The authors report a case of the acantholytic squamous cell carcinoma of the oral cavity in a 36-year-old man. Smeared slides from the FNA were fixed in 95% ethanol and stained with the Papanicolaou stain. A computerized tomographic scan demonstrated a mass of the left buccal mucosa, measuring 1.6 x 1.3 cm. Then, wide excision was carried out. Results: The FNA showed hypercellularity. Malignant cells arranged in isolation, loosely cohesive groups and a linear configuration. Such cells were round to elongated, with vesicular nuclei and prominent nucleoli. Cells possessed occasional intracytoplasmic vacuoles, misinterpreted on FNA to be vasoformative features as seen in malignant endothelial cells. The cytologic diagnosis was “positive for malignancy, suggestive of angiosarcoma”. An excision was performed and by histology, the tumour was diagnosed as acantholytic squamous cell carcinoma. The malignant cells were positive by immunostaining for AE1/AE3, p40, p63 and vimen- tin, but negative for CD31, CD34 and ERG. The intracytoplasmic vacu- oles were PAS- and mucin-negative and negative for the above antibodies. Conclusion: This case highlights the diagnostic challenges on cytol- ogy when malignant acantholytic squamous cells show intracytoplas- mic vacuoles, and stresses how immunohistochemistry is important