A 62-year-old man was given tracheal intubation for chest tightness after detecting SARS-CoV-2 using real-time (RT-PCR) in sputum samples during a week of hospitalization at a local hospital. The patient was then diagnosed with critical COVID-19 using computed tomography (CT) (Figure. 2a) after being transferred to the ICU of our hospital on 29 January 2020. On the third day, he showed diarrheal symptoms with bloody stool, which gradually improved in the following five days. Until the seventh day, the fecal occult blood test reports were negative, but respiratory difficulties continued to aggravate. After two weeks, the patient was provided with veno-venous extracorporeal membrane oxygenation (VV-ECMO) treatment and re-developed bloody stool the next day. Abdominal enhancement CT indicated sigmoid colon occupation (Figure. 2b) and colonoscopy suggested carcinoma. After two tests for SARS-CoV-2 nucleic acid showed negative results and the body temperature returned to normal, the patient underwent radical resection of sigmoid cancer and colostomy on 21 February 2020. Family members living with him, including his wife, son, and daughter-in-law, were released from quarantine after being tested negative for SARS-CoV-2 using nucleic acid tests. The key clinical features are summarized in Fig. 1.
Macroscopic examination showed a 6.5⋅5.0 cm ulcerated and necrotic mass in the middle of the sigmoid colon. Histological examination revealed that the tumor surface and lumen were necrotic, presented a tubular glandular and sylph-like arrangement, and showed the infiltration of peritumor fibrotic stroma by a large number of inflammatory cells (Fig. 3a).
IHC staining showed that CK20, CDX-2, and mismatch repair marker (MSH2, MSH6, MLH1, and PMS2) expression were positive, while CK7 and CMV expression were negative in the tumor cells. Furthermore, MUC2 was negatively expressed in the tumor cells (Fig. 3b). Compared with that in the surrounding enterocytes, ACE2 expression, located in the cell membrane and cytoplasm of tumor cells, were significantly enhanced (Fig. 3c). Two tissue microarray composed of 103 carcinoma tissues and 183 enterocyte were generated to validate that ACE2 expression percentage was very high in both carcinoma and enterocytes (93.2% and 75.4%, respectively), but its intensity was higher in carcinoma than that in controls, the strongly positive ACE2 expression being 73.8% in the tumor, while being only 4.4% in the enterocytes (Table 1). In colon cancer cells, SARS-CoV-2 nucleocapsid expression was localized in the cell membrane and cytoplasm (Fig. 3d), however, all tissue microarray samples showed negative expression. CD3, CD4, CD8, CD20, CD56, CD163, TIA-1, GrB, and PD-1 expression in tumor microenvironment were immunohistochemically assessed. The results revealed that the majority of infiltrated immune cells are mononuclear phagocyte, followed by some T lymphocytes, but minimal natural killer (NK) cells infiltrated ration, which express CD163 (Fig. 4a), CD56 and CD3 (Fig. 4b) respectively. CD20 showed limited expression in the germinal center. The proportion of CD4 and CD8 positive T cells was similar. The percentage of CD8 + T cells producing the cytotoxic molecule were further assessed. TIA-1, GrB (Fig. 4c), and PD-1 (Fig. 4d) were detected in a limited number of infiltrating CD8 + T cells, with TIA-1/CD8, GrB/CD8, and PD-1/CD8 being 0.22, 0.20, and 0.34, respectively.
Table 1
ACE2 expression in tissue microarrays having 103 colorectal cancer and 183 enterocyte cases
| Total | Colorectal carcinoma | Enterocyte | P value |
ACE2 Level | 283 | 103 | 183 | < 0.0001 |
0 | 51 | 7(6.8%) | 45(24.6%) | |
1 | 150 | 20(19.4%) | 130(71.0%) | |
2 | 84 | 76(25.2%) | 8(4.4%) | |