ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 CD117, Dog1, ALK-1, Desmin and Inhibin-alpha were negative. The lesion was diagnosed as calcifying fibrous tumour. The ovarian cysts were yellow body haemorrhagic cysts and follicular cysts. Conclusion: The CFT is a rare tumour with a distinctive histologi- cal presentation. That usually occurs in children and young adults. Several sites have been reported but predominantly in the gastro- intestinal tract. Usually presented as a solitary lesion, however, multifocal tumours have been observed in up to 10% of cases, in some studies. The diagnosis is based on histology, because clinical and radiological features are nonspecific. Awareness of this entity is crucial to distinguish it from peritoneal carcinosis and other mesenchymal tumours. E-PS-06-037 An unexpected Lynch Syndrome patient, Muir torre variant R. D’Amato Pascarella*, M. Cerati, A.M. Chiaravalli, I. Carnevali, F. Sessa *University Hospital of Insubria, Varese, Italy Background & objectives: As immunotherapy is now FDA approved as first-line setting in metastatic or unresectable mismatch repair (MMR) defective gastrointestinal tumours it has become even more crucial to identify them. Methods: A peculiar case of a 52 years-old male with an important weight loss, jaundice with hyperbilirubinemia and increased of the other hepatic markers. No apparently relevant past medical history was reported. He underwent routine blood tests, tumoral markers and further investigation through imaging revealed dilatation of the intrahepatic biliary ducts and a polypoid mass of the papilla. Results: Microscopically after formalin-fixation, paraffin- embedding, hematoxylin-eosin fixation and immunohistochemical stain the diagnosis of ampullary adenocarcinoma was made. Taking into account the young patient age his medical history was further investigated and were taken aback by what we discovered. Ten years before he was diagnosed with a sebaceous adenoma with the loss of MSH2/MSH6 MMR proteins. With this new information we tested the ampullary tumour for MMR protein expression and the result was the same; also, his family history was significant. NGS molecular analysis of MSH2, MSH6 and EPCAM genes dis- covered a pathogenic variant of MSH2 gene. Considering all the data the patient was labelled as LS, Muir-Torre variant. Conclusion: This is a remarkable example of how important is not only to make the correct diagnosis but also to always evaluate the medical and familiar history of patients which is crucial to identify LS or MMR defective patients but also to give them the best pos- sible therapeutic opportunity since the advent of tissue-agnostic anti-cancer drugs. E-PS-06-038 Morphogenetic role of mast cells in colorectal cancer A. Filin*, E. Chupandina, V. Shishkina, A. Goryacheva *Voronezh State Medical University, Russia Background & objectives: Mast cells are found in various tumours and one of the main cells of the tumour microenvironment with differ- ent effects. However, the assessment of the role of mast cells in tumour morphogenesis does not always give an unambiguous result Methods: 46 patients with diagnosed colorectal cancer and detected mast cells by immunohistochemical method, on paraffin sections using monoclonal mouse antibodies to Tryptase and Chy- mase. Mast cells ware quantified in the tumour and at the invasive margin of the tumour. The degree of mast cell degranulation was also determined. Results: The mast cells are widely represented in the tumour microenvironment, but predominate in the invasive margin of the tumour rather than in its centre. At the same time, the functional activity of mast cells was distributed in the opposite way. Mast cells with the greatest degranulation were just observed in the tumour itself. And in the invasive region, mast cells were functionally less active or inactive, despite the quantitative advantage. Quantitative assessment of mast cells revealed no correlation with life expectancy, the presence of regional metastases. There is a decrease in the amount of cells with a decrease in the degree of differentiation of the tumour (in the invasive region). Conclusion: Mast cells are widely represented in the tumour microenvironment in colorectal cancer. There is a significant advantage in their number in the invasive edge of the tumour. But it is impossible not to take into account their functionality. The decrease in the number of mast cells in the tumour tissue may be due to their increased activity in this area, and not to their exclu- sion from the morphogenetic process. E-PS-06-039 Visceral leishmaniasis presented as colitis in a patient with multiple myeloma A. Sykaras*, C. Kouvidou *Department of Pathology, Evangelismos General Hospital, Ath- ens, Greece Background & objectives: Visceral Leishmaniasis (VL) is a poten- tially fatal parasitic disease and the most severe form of Leishmaniasis caused by protozoa of the species Leishmania. VL usually affects the bone marrow, the liver and the spleen of immunocompromised patients. Methods: A 67-year-old man was admitted with persistent bloody diarrhea. The patient was immunosuppressed with a medical his- tory of renal transplantation and multiple myeloma under treat- ment. Colonoscopy findings included erythema, oedema, ero- sions-ulcers and pseudopolyps distributed in a continuous fashion suggesting inflammation of the entire colon. Multiple biopsies were taken from all colon segments. Results: Histological examination of large intestinal mucosa was compatible with the endoscopic findings of colitis revealing a mild crypt architectural distortion, mucosal surface erosions and a moderate to severe neutrophilic and eosinophilic inflammatory infiltration of the lamina propria. Moreover, a striking finding in all biopsy samples was the presence of numerous macrophages (some of them enlarged) in the lamina propria, containing abun- dant and dense intracytoplasmic microorganisms. Their morphol- ogy (round to oval, uniform and hematoxylinophilic) was strongly suggestive of Leishmania amastigotes. Giemsa histochemical stain also highlighted the morphology of Leishmania parasites. The diagnosis of Leishmania infection was confirmed by sero- logical tests and the patient responded well to the treatment with amphotericin B. Conclusion: The involvement of the gastrointestinal tract is unu- sual in Leishmaniasis and is considered as an atypical feature of VL. Intestinal VL affects mainly the duodenum whereas colonic VL is extremely rare and has been reported predominantly in immunosuppressed patients. Colonic VL may present macroscopi- cally as colitis but usually the musosa appears normal and the diagnosis is based on the histological findings. Pathologists should be aware of the presence of Leishmania parasites in colon biopsies from immunocompromised patients with diarrhea. S227