Abstract
Background: Colorectal cancer is the third most commonly diagnosed cancer in both men and women, and one of the more widely recognized preventable cancers. Adenosquamous carcinoma (ASC) of the colon/rectum is an uncommon disease that consists of both glandular and squamous components, and the most common site of ACS is the right and transverse colon. Case Report: Here, we present the case of a 78-year-old woman, who complained of abdominal pain. Colonoscopy revealed a circumscribed tumor in the ascending colon, and no specific lesion was detected in the other areas of the colon or rectum. ASC (pT3N0M0) was diagnosed from right hemicolectomy specimens. Three months after the first surgery, the serum levels of tumor markers had gradually increased, and a new tumor was subsequently detected in the sigmoid colon 2 months later. The sigmoid lesion was surgically resected and diagnosed as ASC (pT3N3M0). Strong PD-L1 expression was also found in the squamous component. Conclusion: To our knowledge, this is the first report of a recurrent sigmoid colon ASC that likely originated from the ascending colon, and PD-L1/PD-1 signaling was likely involved in the immune escape mechanism.
Adenosquamous carcinoma (ASC) of the colon/rectum is an uncommon disease that consists of both glandular and squamous components (1, 2). ASC of the colon accounts for 0.02% to 0.06% of all colorectal malignant tumors. The first case was reported by Herxheimer in 1907 (3). The most common site of ACS is the right and transverse colon (4, 5). Although the clinical manifestations are similar to those of adenocarcinoma, ASC is associated with a poor clinical outcome, with a 5-year overall survival rate of 31%, in comparison to conventional adenocarcinoma (4). ASC has a greater tendency to form both regional and distant metastases, and similar to colorectal adenocarcinoma, the most common metastatic site is the liver, followed by the peritoneum and lung (4). The overall rates of regional metastases and distant metastases were reported to be 46.0% and 42.4%, respectively. In a review of Japanese patients with ASC, Yokoi et al. reported that 48% were female, 56% had right-sided colon cancer, 94% were T3 or more, 62% had lymph node metastasis, and 33% were stage IV (6). ASC has been reported to be aggressive, and is diagnosed at advanced stages. Herein, we report a case of recurrent intestinal ASC suspected to be due to implantation metastasis from the ascending colon to the sigmoid colon. In addition, immunohistochemical analysis of the primary and recurrent lesions was performed. We found strong PD-L1 expression in the squamous component, and the level of PD-L1 expression was increased in the recurrent lesion; therefore, immune escape via PD-L1/PD-1 signaling may be involved in the progression of ASC.
Case Report
A 78-year-old Japanese woman was referred to our hospital with a history of abdominal pain. She had a medical history of asthma and ovarian benign tumor. Diagnostic colonoscopy revealed the presence of a large circumferential and obstructive 6-cm mass. No detectable lesion was seen in the sigmoid colon. Biopsy of the mass indicated carcinoma; however, a detailed histological diagnosis was not obtained. The serum levels of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) were 27.8 ng/ml (normal range=0-5.0 ng/ml) and 78.9 U/ml (normal range=0-37 U/ml), respectively. The squamous cell carcinoma (SCC) antigen level was not measured. Abdominal computed tomography demonstrated thickening of the wall of the ascending colon and no distant metastasis. The patient underwent a right hemicolectomy with D3 lymph node dissection together with partial resection of the duodenum. The pathological diagnosis was ASC without lymph node metastasis (pT3N0M0; Stage IIa). She was followed-up without adjuvant chemotherapy. However, the serum levels of CEA gradually increased 3 months after the first surgery, and a tumor mass was subsequently detected 2 months later in the sigmoid colon by computed tomography and colonoscopy. The CA19-9 levels were also elevated. Biopsy of the tumor revealed a poorly differentiated adenocarcinoma. The values of CEA and CA19-9 before the second operation reached 27.4 ng/ml and 56.4 U/ml, respectively, and the SCC antigen value was 1.2 ng/ml (normal range=0-1.5 U/ml). The patient underwent a sigmoidectomy with D3 lymph node dissection. The pathological diagnosis of the recurrent lesion was ASC (pT3) with lymph node metastasis. She received postoperative adjuvant chemotherapy with a capecitabine plus oxaliplatin regimen for 4 months. No subsequent recurrent lesion has been seen, and all three tumor markers are within normal limits.
Pathological observation. A circumferential mass lesion with ulceration and a 5-cm diameter was seen, and a whitish solid tumor was observed in the cross-section of the lesion (Figure 1A). The solid tumor had an atypical glandular (adenomatous) structure that indicated grade 1 to 2 (well-to-moderately differentiated) adenocarcinoma, and a solid nest pattern that indicated grade 2 SCC (Figure 1B). The ratio of the adenomatous and squamous components was approximately 1:1, and both components were sequentially converted. Fibromatous stroma and immune cell infiltration were also detectable. As shown in Figure 1C, immunohistochemistry (IHC) of cancer tissue showed that the adenomatous component was positive for CK20, and the squamous component was positive for p40 and CK5/6, which is consistent with ASC. Mutations of the RAS gene and microsatellite instability (MSI) were negative, whereas the BRAF (V600E) mutation was detected.
The recurrent lesion was a similar all-around mass lesion with ulceration that was 4 cm in diameter, and a whitish solid tumor was observed in the cross-section of the lesion (Figure 2A). It was hypothesized to be a rapid growth tumor. The tumor was composed of grade 1 to 2 ADC and grade 2 SCC, similar to the primary lesion, and was consistent with ASC (Figure 2B). The adenomatous and squamous components comprised 10% and 90% of the tumor, respectively. Two regional lymph node metastases were observed, and the histology of the lymph node metastases was consistent with ASC. The IHC results were the same as those of the primary lesion (Figure 2C). Additional IHC showed positive CEA and CA19-9 staining in both the adenomatous and squamous components (Figure 2C). Both components were also positive for mismatch repair molecules, such as MLH1, MSH2, MSH6, and PMS2 (data not shown). No positive signals of p53 were observed in either of the components, which indicated the so-called “p53-null mutation” (data not shown).
Additional IHC studies were performed, and p40 and CK20 double-positive cells were sporadically observed in the tumor lesion, especially in the transitional zone between the adenomatous and squamous components (Figure 3A). Notably, PD-L1 overexpression was observed in the squamous component, but not in the adenomatous component (Figure 3B). Over 90% of the squamous component was positive for PD-L1. Stromal immune cells, mainly macrophages, were also positive for PD-L1.
Discussion
ASC of the colon is often detected at an advanced clinical stage, when the tumor is already large, and is characterized by a higher incidence of lymph node metastasis when compared to pure adenocarcinoma. The most common site of colorectal ASC is the right and transverse colon, and the liver is the most common site of metastases, followed by the peritoneum and lung (7). The present case showed stage T3 disease without lymph node metastasis in the primary lesion, and recurrence in the sigmoid colon 5 months after the first operation. Even in common colorectal cancer, hematogenous metastasis from the right colon to the sigmoid colon has rarely been reported (8).
The gross appearance and histological growth pattern of the recurrent lesion were similar to those of the primary lesion, indicating that the recurrent lesion originated from the mucosal area. Colorectal cancer spreading by implantation is also rare; however, it has been described in colonoscopic biopsy sites, laparoscopic port sites, and others (9, 10). Since the incidence of ASC is very rare, the de novo carcinogenesis of ASC in other sites has not been clarified. Therefore, implantation metastasis from the ascending colon to the sigmoid colon may have caused the recurrence of ASC in the present case.
Although both the adenomatous and squamous components have the potential for metastasis in ASC of the colon, more aggressive potential was observed in the squamous component (11-13). In the present study, the ratio of the squamous component was significantly higher in the recurrent lesion than in the primary lesion, indicating that SCC is more aggressive than adenocarcinoma. The histogenesis of ASC is not fully understood, despite the fact that previous studies have suggested several hypotheses, i.e., the presence of embryologic nests of ectodermal cells, squamous metaplasia of the intestinal mucosa, and the presence of pluripotent stem cells of endodermal origin that are capable of multidirectional differentiation (14, 15). In a previous gene sequence analysis of ASC of the pancreas, TP53 mutations and 3p deletions were frequently observed (16). This study also found that the adenomatous and squamous components shared crucial mutation events and similar genomic variations, suggesting that the two cellular components may develop from the same progenitor cancer cells. In the present case, p40 (SCC marker) and CK20 (adenocarcinoma marker) double-positive cells were sporadically observed in the tumor tissues, supporting the hypothesis that the two components are derived from the same pluripotent stem cells or progenitor cancer cells.
In the present study, IHC for p40 was performed to confirm the pathological diagnosis. p40 is one of the p63 isoforms (ΔNp63) that has been identified in recent years to be specifically expressed in SCC (17). The sensitivity and specificity of p40 for SCC has been reported to be 90% to 100% in lung cancer and head and neck cancer. Since the squamous component of the present ASC case was also positive for p40, IHC for p40 might be useful for the diagnosis of ASC in the intestine.
Another interesting result of IHC in this case was that PD-L1 expression was restricted to the squamous component and was not observed in the adenomatous component. PD-L1 expression in colorectal adenocarcinoma has been reported to be around 30% (18). In lung cancer, PD-L1-positive cancer cells were observed in 72% of SCC cases and 27% of adenocarcinoma cases (19, 20). Thus, squamous cancer cells potentially express more PD-L1 than adenocarcinoma cells. In addition, immune checkpoint inhibitors (ICIs) have shown efficacy in patients with MSI-high/mismatch repair-deficient (MSI-H/dMMR) cancers. A recent report described the successful treatment of MSI-H colorectal cancer by anti-PD-1 antibody (21). It has also been reported that a case with metastasized colon ASC, in which the squamous component expressed PD-L1, was successfully treated by anti-PD-1 antibody therapy (22). High levels of PD-L1 expression were also observed in the squamous component in both the primary and recurrent lesions in the present case. A high PD-L1 expression level on tumor cells predicts a beneficial anti-tumor effect of anti-PD-1/PD-L1 therapy in non-small cell lung cancer, head and neck cancer, and melanoma (23, 24).
Although few reports on PD-L1 expression in colorectal cancer have been published, there have been several reports on PD-L1 expression in ASC of the lung, uterine cervix, and pancreas (Table I). From four studies describing PD-L1 in lung ASC, 68 of 157 cases (43.3%) were positive for PD-L1, and PD-L1 was preferentially expressed in SCC (25-28). Two of the four studies described the anti-cancer effect of ICIs in lung ASC; they reported that 4 and 2 of 6 cases showed a partial response and progressive disease, respectively, and that the efficacy of ICI therapy appeared to be higher in ASC than in other cancers with common histological subtypes (29, 30). In a report of ASC of the uterine cervix, 3 of 7 cases were positive for PD-L1, and PD-L1 expression was restricted to SCC (31). Two studies reported PD-L1 expression in pancreatic ASC. Lee et al. showed that 6 of 56 cases were positive for PD-L1, and that the PD-L1-positive ratio was similar to that of ADC, which is a common histological subtype of pancreatic cancer (32). Tanigawa et al. reported that 5 of 6 cases of pancreatic ASC were positive for PD-L1, and that PD-L1 expression was restricted to SCC (33). Several different monoclonal antibodies against PD-L1 are commercially available, but their sensitivity and specificity have been reported to vary (34); as such, the use of different antibody clones might cause discrepancies between the results of different studies.
Taken together, SCC in ASC preferentially expressed PD-L1 in several organs. Although patients with ASC generally show a worse clinical course than those with the usual adenocarcinoma in several organs, ICI therapy targeting PD-1/PD-L1 might be a promising approach for patients with recurrent or metastatic ASC.
Acknowledgements
The Authors would like to thank Mr. Takenobu Nakagawa for a technical assistance. The Ethics Committees of Kumamoto University approved the content of this manuscript (#2224), and written informed consent was obtained from the patient before surgery. Written informed consent was obtained from the patient for publication of this case report and any accompanying images.
Footnotes
Authors’ Contributions
SA and KY gathered the patient`s data and wrote the manuscript. SA, KY, EO, NS, HY, KY, and TB participated in the surgery. YK and DY were responsible for pathological diagnosis of this case. SA, KY, YK, DY, EO, NS, HY, KY, and TB discussed the data and helped write the manuscript. All Authors approved the final manuscript.
Conflicts of Interest
The Authors declare no conflicts of interest associated with this manuscript.
- Received July 16, 2021.
- Revision received September 14, 2021.
- Accepted September 15, 2021.
- Copyright © 2021 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.