ECP 2023 Abstracts

S212 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: The described clinical cases draw attention to the underes- timated role of chromogranin A expressing cells of the colonic mucosa as a component of the pathogenesis of slow transit constipation. Further study of the pathogenesis of slow transit constipation can reduce the number of unjustified surgical interventions. E-PS-06-076 A case of acute appendicitis as a result of actinomycosis E. Psychogiou*, P. Tziakou, P. Megas, M. Miliou, K. Papadopoulou, A. Konstantinidou, E. Papadopoulou, D. Riga, C. Glava, I. Vamvakaris *General Hospital of Athens Sotiria, Greece Background & objectives: Actinomycosis is a rare, indolent, and multisystemic infection caused by Actinomyces, bacteria of the oral and intestinal flora. It affects the abdominal region and the most com- mon presentation is a perforated appendix. Symptoms are nonspecific, which makes differential diagnosis challenging. Methods: A 36-year-old man was admitted to our hospital with abdom- inal pain in the periumbilical and right lower quadrant areas. Acute appendicitis was diagnosed and appendicectomy was performed. The surgical specimen measured 6,5X1,5 cm with haemorrhagic and pseu- domembranous inflammatory serosal surface. Results: The histologic examination revealed characteristic clumps of basophilic filamentous bacteria in a vaguely rosette-like configuration surrounded by acute inflammatory cells. With higher magnification, a typical sulfur granule surrounded by neutrophils was found. Also, transmural inflammation, lymphoid hyperplasia were identified, along with mucosal ulceration and architectural distortion. At the submu- cosa, the outer portion of the abscess showed evidence of organization, with vascularized granulation tissue and fibrosis in addition to chronic inflammatory cell infiltration. The Actinomyces colonies were compat- ible with the diagnosis of appendicular actinomycosis. Microbiological exams of the patient were negative. Conclusion: We report this case due to the rarity of this entity, high- lighting the importance of considering actinomycosis in the differential diagnosis of an intrabdominal mass or unspecific, recurrent abdominal pain, especially if it has an insidious, chronic evolution. It is mostly diagnosed post-operatively by histological analysis. The combined therapy of surgery and antibiotic appears to cure more than 90% of actinomycosis, having an excellent outcome in avoiding recurrence, especially when the infection is treated in an early stage. E-PS-06-077 A rare intestinal deposition of a common material: not everything is melanosis. P. Puente López*, G. Escuer, C. Saus Sarrias, L. Guerra Pastrián, E. Palacios Lázaro *La Paz University Hospital, Spain Background & objectives: Deposits in the gastrointestinal tract are relatively frequent. They have a broad differential diagnosis and can be classified into two types: pigmented (melanosis, pseudomelanosis, brown bowel syndrome, hemochromatosis, barium granuloma, tattoo, melanoma) and non-pigmented (xanthoma, muciphages, pseudolipo- matosis, infectious diseases, malakoplakia). Methods: For this biopsy, a radiological examination of the sample was carried out and histochemistry techniques PAS and Perls were used for the histological evaluation. Mass spectrometry and scanning microscopy are also performed. Results: 84-year-old male who underwent a colonoscopy for consti- pation, showing a whitish stellate area of 10mm, flat, with a normal mucosal pattern that was biopsied. We received several fragments of large intestine mucosa in which the mucosa does not show epithelial dysplasia, what is striking is that in the lamina propria there are macrophages, with a golden pigment that is refractile but not birefringent, which are intermingled with muscle bundles. The pigment is negative for Perls and PAS; therefore, an X-ray of the block is performed, showing radiopaque material. Mass spectrometry and scanning microscopy were performed, in which abundant deposits of barium and sulfur compatible with barium sulfate were observed. Conclusion: A common finding in daily practice is the presence of deposits in the intestine, being more frequent the pigmented ones. The morphologic and histochemical characteristics of these materials are fundamental for their differential diagnosis. The barium sulfate deposit presents as a refractile but not birefringent and radiopaque material. This material can cause chronic granulomatous inflam- mation, raising the differential diagnosis with inflammatory bowel disease. E-PS-06-078 The adenoma-carcinoma sequence in third pathway of colonic carcino- genesis (GALT) adenocarcinomas: 3 case report and literature review D.G. Puppa*, D. Turberg, G. Arnoux, C. Rubio *Centre Médicale Univers. (HUG), Switzerland Background & objectives: Little is known regarding the origin and the precursor lesion of the GALT carcinoma which despite having a favourable prognosis is not included in the current WHO classification. We report a case series covering the adenoma-carcinoma sequence in GALT neoplasia. Methods: Three original early cases are reported with morphological, pathological staging, molecular and electron microscopy study features with follow-up. All the cases described in the litterature under the terms “dome” and “GALT” are reviewed. Results: From our archives the following cases were selected: 1) a tubular adenoma with typical histological GALT features, 2) a tubular adenoma with malignant transformation with GALT features both in the adenomatous and in the invasive components (pT1 N0), 3) a tubular adenoma with malignant transformation and deep wall invasion show- ing superficially GALT features (pT3b N0). Conclusion: A GALT differentiation can be identified not only in the adenocarcinoma but also in the pre-invasive adenoma. This variant is likely underecognized when limited to the superficial part of the tumour and shouldn’t be missed. Our findings support the already proposed Third Pathway model of Colonic Carcinogenesis. The lack of adverse morphological features, synchronous metastasis and recurrences in this series as well in the literature are consistent with a low-risk histotype thus deserving to be added to the WHO classification. E-PS-06-079 Mixed adenocarcinoma arising in Meckel’s diverticulum: a case report P. Rodrigues Veiga*, J. Fraga, A. Lapa *Pathology Department, IPO Porto, Portugal Background & objectives: Meckel’s diverticulum (MD) represents the most common congenital malformation of the gastrointestinal tract and is caused by incomplete obliteration of the vitelline duct during intrauterine life. Malignant transformation is very rare, with carcinoid tumours being the most common. Methods: We describe a case of a 32-year-old man that presented with a suspected Meckel’s diverticulitis associated with intestinal obstruction. He was submitted to segmental enterectomy. The post-op was complicated with peritonitis and dehiscence of the anastomosis. Terminal ileum resection and terminal ileostomy were performed. Results: The histopathological examination revealed a poorly differen- tiated mixed adenocarcinoma arising in a diverticulum with all layers of the small bowel compatible with MD. The tumour showed mainly tubule-papillary and poorly cohesive areas, which was invading the