SARS-CoV-2 identified by transmission electron microscopy in lymphoproliferative and ischaemic intestinal lesions of COVID-19 patients with acute abdominal pain: two case reports

Abstract

Background: SARS-CoV-2 may produce intestinal symptoms that are generally mild, with a small percentage of patients developing more severe symptoms. The involvement of SARS-CoV-2 in the physiopathology of bowel damage is poorly known. Transmission electron microscopy (TEM) is a useful tool that provides an understanding of SARS-CoV-2 invasiveness, replication and dissemination in body cells but information outside the respiratory tract is very limited. We report two cases of severe intestinal complications (intestinal lymphoma and ischaemic colitis) in which the presence of SARS-CoV-2 in intestinal tissue was confirmed by TEM. These are the first two cases reported in the literature of persistence of SARS-CoV-2 demonstrated by TEM in intestinal tissue after COVID 19 recovery and SARS-CoV-2 nasopharyngeal clearance.

Case presentation: During the first pandemic peak (1st March-30th April 2020) 932 patients were admitted in Hospital Universitari Mútua Terrassa due to COVID-19, 41 (4.4%) required cross-sectional imaging techniques to assess severe abdominal pain and six of them (0.64%) required surgical resection. SARS-CoV-2 in bowel tissue was demonstrated by TEM in two of these patients. The first case presented as an ileocaecal inflammatory mass which turned to be a B-cell lymphoma. Viral particles were found in the cytoplasm of endothelial cells of damaged mucosa. In situ hybridization was negative in tumour cells, thus ruling out an oncogenic role for the virus. SARS-CoV-2 remained in intestinal tissue 6 months after nasopharyngeal clearance, suggesting latent infection. The second patient had a severe ischaemic colitis with perforation and SARS-CoV-2 was also identified in endothelial cells.

Conclusions: Severe intestinal complications associated with COVID-19 are uncommon. SARS-CoV-2 was identified by TEM in two cases, suggesting a causal role in bowel damage.

Keywords: COVID-19; Case report; Intestinal lymphoma; Ischaemic colitis; SARS-CoV-2; Transmission electron microscopy.

Fig. 1

COVID-19 patients operated during the first pandemic peak (from March 1 to April 30, 2020). This figure shows the diagnoses, histological and transmission electron microscopic findings of patients operated during the first peak of the pandemic in our hospital

Fig. 2

Complementary examinations (CT scan, colonoscopy, light microscopy and transmission electron microscopy) from case 1. A, B Coronal contrast-enhanced computed tomography (CT) scan at the moment of diagnosis (A) and after COVID-19 treatment (B). Panel A shows luminal narrowing and marked wall thickening involving the ascending colon, caecum, and terminal ileum. Panel B shows significant decrease in the wall thickening of the colon and terminal ileum, the lymph nodes have also decreased in size and number. C Colonoscopy at the level of the caecum reveals a mass of inflammatory appearance that predominantly affects the ileocecal valve, which is stenosed and prevents passage to the terminal ileum. D Haematoxylin and eosin staining of colonic biopsies showing abundant granulation tissue with lymphoplasmacytic inflammation and vascular proliferation (×200). E Electron micrograph of a portion of an endothelial cell showing several viral particles (red circles) lying apparently free in the cytoplasm, all separate from each other. F Close-up electron micrograph of one of the viral particles in E. The virus surface protrusions (red circle) are distinguished from confounding structures, such as ribosomes in tangential sections of the rough endoplasmic reticulum (red arrow), by the more geometric, lighter, hollow-looking appearance of the former

Fig. 3

Complementary examinations (intestinal resection specimen, light microscopy and transmission electron microscopy) from case 1. A The ileocaecal resection specimen showed an ulcerated lesion with fibrosis of the intestinal wall, causing stenosis. B Haematoxylin and eosin staining of the surgical specimen showing diffuse large B-cell lymphoma germinal center subtype. Lymphocytes of medium and large size with irregular nuclei, vesicular chromatin, conspicuous nucleoli and mitotic figures were observed (×100). C- D Immunohistochemistry of the lesion was performed, showing expression for CD20, CD79a, bcl2, CD10, bcl6, LMO2, MUM1, and c-MYC. The tumour was classified as diffuse large B-cell lymphoma (DLBCL) germinal center subtype. In panel C, CD20 (clone L26, Ventana, Roche, Tucson, AZ, USA) immunohistochemistry is shown (×100). In panel D, a high proliferative index (Ki67) (clone 30-9, Ventana, Roche, Tucson, AZ, USA) was observed (90% in the hotspot areas) (100x). E- F Electron micrograph of the lymphoma tissue, in which viral particles are highlighted (red circles). E Viral particles (red circle) remained in occasional endothelial cells. F In contrast to coronavirus particles (red circle), pinocytotic vesicles (red arrow) have a smooth contour, their cell membrane lipid bilayer may be visualized, and they are often arranged in clusters

Fig. 4

Time course of the patient's 1 (A) main events. This figure shows the main events and complications of the case 1. The first row of the table shows the dates of the events, and the first column describes the complementary examinations carried out

Fig. 5

Complementary examinations (PA Chest X-ray, CT-scan, light microscopy and transmission electron microscopy) from case 2. A PA chest radiograph shows ground-glass opacification of bilateral perihilar region and the peripheral middle third of the right hemithorax. B Abdominal contrast-enhanced CT showing a short stenosis of the proximal transverse colon with mild involvement of the pericolic fat and proximal dilation of the ascending colon and small intestine (white arrow). C-D Haematoxylin and eosin staining of the surgical specimen. C Mucosal necrosis, haemorrhage, and submucosal oedema were observed (×40). D Transmural ulcer showed abundant granulation tissue, chronic inflammation, fibrosis, and steatonecrosis, findings consistent with intestinal ischaemia (×200). E Electron micrograph of the surgical specimen showing virus particles (red circle) in an oedematous, damaged endothelial cell. F Low-power high-resolution electron micrograph with markedly oedematous endothelial cells and pericytes, congested capillaries with red blood cells and platelets, endothelial cell containing enlarged nuclei and active nucleoli. All these features are a reflection of endothelial cell stress, damage, and reactive changes

Fig. 6

Time course of the patient's 2 (B) main events. This figure shows the main events and complications of the case 2. The first row of the table shows the dates of the events, and the first column describes the complementary examinations carried out