ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 risk of metastatic disease, but in our case the tumour was detected in an early stage and was confined to the Ampulla. After 2 months the patient is alive and well without signs of relapse. Further inves- tigation is needed to expand our knowledge and improve diagnosis and treatment of these patients. E-PS-06-020 Intestinal obstruction as initial manifestation of lobular breast cancer metastasis. A case report G. Galanopoulos*, E. Souka, N. Novkovic, C. Dastamani, E. Tso- volou, K. Manoloudaki *Pathology Department Metaxa Cancer Hospital, Greece Background & objectives: Breast cancer is the most prevalent malig- nancy affecting women, usually metastasizing to the bones, lung and liver. Gastrointestinal tract metastases are rare, mostly involving the stomach. An unusual case of lobular breast cancer primarly detected as abdominal carcinomatosis is presented. Methods: A 49-year-old woman without a known history of breast cancer was admitted with ileus, having mentioned only minor symptoms of dyspepsia during the last 6 months. The exploratory laparotomy revealed massive carcinomatosis affecting the perito- neum, ovaries, cecum and transverse colon. Bilateral salpingo- oophorectomy, right hemicolectomy and partial peritonectomy were performed. Grossly, the tumour areas had a brownish micro- nodular appearance. Results: Microscopically, the tumour consisted of small sized cells with round or ovoid nuclei and scant cytoplasm arranged in single files, cords and nests. The immunohistochemical analysis showed positive staining for CK7, GATA 3, GCDFP-1, CK903, P120 and negative for CDX2, CK20, and e-cadherin. ER and PR receptors were strongly positive (80% and 40% respectively). Her2/neu was negative (1+). Both morphological and immunohistochemical results confirmed the diagnosis of metastatic lobular breast cancer. No abnormal findings were found on breast ultrasound and digital mammography that followed. Conclusion: Abdominal carcinomatosis of breast cancer has a prevalence of 0.7% and can be detected on initial diagnosis in some cases. Since the signet-ring morphology of lobular carcinoma may mimic gastric carcinoma, differential diagnosis may be challeng- ing. Even with a known history of breast cancer, abdominal metas- tases can be overlooked on a long disease-free interval. Immu- nohistochemical analyses are necessary in the majority of cases. E-PS-06-021 Crawling-type gastric adenocarcinoma with progression to signet-ring cell (diffuse) carcinoma M. Souto de Moura*, I. Gullo, C. Fleming, C. Peixoto, J. Lopes, C. Fátima *Department of Pathology, IPO-Porto, Portugal Background & objectives: Crawling-type gastric adenocarcinoma (CTAC), also designated as intestinal-type adenocarcinoma with anastomosing glands, is a rare variant of gastric cancer with specific morphological and molecular characteristics. We present two cases of CTAC and review the morpho-molecular features of this rare entity. Methods: Case 1: 61-year-old woman referred to our hospital with the diagnosis of diffuse/signet-ring cell (SRC) carcinoma of the antrum. Endoscopy revealed a 1.2x1.0 cm lesion, slightly elevated and centrally depressed, removed by endoscopic submucosal dis- section (ESD). Case 2: 77-year-old woman referred for SRC carcinoma of the incisura. Endoscopy revealed focal irregularity of gastric mucosa with 0.5x0.2 cm, removed by ESD. Results: Both lesions consisted of branching, anastomosing, “letter-shaped” glands with low-grade atypia. Intramucosal diffuse (SRC) carcinoma (pT1a) was identified adjacent to the glandular component, representing a major part of the lesion in case 1 and only a small focus in case 2. Neoplastic glands displayed gastric phenotype in case 1; by immunohistochemistry, there was expression of MUC5AC and MUC6 in the glandular component; intestinal markers (CDX2, CD10, and MUC2) were negative and the SRCC component showed abnormal E-cadherin expression. Case 2 was almost entirely constituted by anastomosing glands with goblet cells, mimicking dystrophic intestinal metaplasia (IM), and IM was observed in the background mucosa. Conclusion: CTAC associated to diffuse (SRC) carcinoma rep- resents a rare subtype of gastric cancer with distinctive morpho- logic and molecular characteristics. Its recognition is crucial, due to the possible progression to diffuse (SRC) gastric carcinoma (doi:10.1007/s10120-012-0173-2), as occurred in our cases. CTAC may harbour molecular alterations typically found in diffuse gas- tric carcinoma (doi:10.1038/s41379-018-0181-9), which offer an explanation for CTAC de-differentiation. Pathologists should be aware of this peculiar entity, also for the importance of distin- guishing CTAC from its mimickers, namely dystrophic intestinal metaplasia. E-PS-06-022 Hepatoid gastric carcinoma metastatic to the skin - a case report C. Valavanis*, N. Novkovic, G. Stanc, S. Stasinopoulou, N. Kopanakis, E. Souka *Molecular Pathology Unit Metaxa Cancer Hospital, Greece Background & objectives: Hepatoid adenocarcinoma of the stomach (HAS) is a rare aggressive tumour with hepatocellular differentiation. Skin metastasis of HAS is an unusual site. It usually occurs in elderly patients and often is diagnosed in advanced stage. Methods: A 87-years-old male was presented to our hospital for a large skin lesion on the back. A skin biopsy was made. There is no clinical history of cancer. Results: The pathologic examination revealed, in the subcuta- neous tissue, an invasive high-grade carcinoma with solid and tubular pattern, intracellular mucin producing cells (signet-ring like cells) and necrosis. Histochemical stains PAS (+), Alcian Blue (+) and PAS-D (-) showed the presence of neutral and acid mucins. The immunohistochemistry was positive for CK7, EMA(MUC1), MUC5AC, CA9/19, HepPar1, TTF-1 (cytoplasmic expression). Ki-67 was positive in 50% of neoplastic cells. Negative immuno- reactivity was found for Napsin A, CK20, CDX2, MUC2, Melan A, HMB45 and S-100. Based on morphological and immunohis- tochemical features a diagnosis of a high grade hepatoid adeno- carcinoma with putative gastrointestinal origin was made. Further investigation confirmed the gastric origin. Conclusion: The HAS is a very rare entity. Making the diag- nosis of this tumour type is a dilemma for the pathologist and the clinician and may lead to misdiagnosis. The main differen- tial diagnosis is with hepatocellular carcinoma, especially if the primary lesion is found in the liver. Due to its rarity, there is no consensus regarding therapy. Treatment of metastatic disease remains to be defined. S222