A Rare Case of Primary Rectal Squamous Cell Carcinoma and the Use of Cytokeratin Markers.

Sindu Iska,Kapisthalam Kumar

doi:10.7759/cureus.21175

Abstract

Lower gastrointestinal cancers are commonly adenocarcinoma of the colon and rectum and squamous cell carcinoma (SCC) of the anus. Rectal squamous cell carcinoma (SCC) is a rare gastrointestinal tract malignancy, as rectal SCC is assumed to be from the migration of anal squamous cells. However, primary rectal SCC is rarer. Here, we present a case of a 63-year-old male who was found to have rectal SCC that was very close to the anus. Through literature review, it was noted that SCC and adenocarcinoma of rectal origin stain positive for cytokeratin CAM 5.2 and not the anal canal lesions. This patient's tumor was positive for CAM 5.2. The patient was treated with 5-fluorouracil and mitomycin C with radiation therapy for five weeks. The post-therapy repeat PET scan showed complete resolution of the tumor and oligometastasis. Unfortunately, the 20-week follow-up PET CT showed para-aortic and retrocrural lymph nodes consistent with malignancy. This case emphasizes the use of immunohistochemical stains for diagnosis and treatment planning in patients with rectal SCC. Once the diagnosis was confirmed, the patient was treated as anal SCC. The importance of differentiating between rectal and anal SCC can be argued, although the treatment is the same; however, the prognosis is worse based on nodal involvement in rectal SCC. Patients with early intervention have a five-year overall disease-free survival of greater than 80%.

Highlights

Colorectal cancer is the third most common carcinoma in the United States [1]
The NCI states that the overall five-year survival for rectal squamous cell carcinoma (SCC) was found to be 48.9% compared with 62.1% for adenocarcinomas [2]
The incidence of primary rectal SCC is rising with time, and the diagnostic criteria for squamous cell cancer involving the rectum include (i) absence of evidence of squamous cell carcinoma of any other part of the body, indicating possible metastasis; (ii) careful proctoscopy/colonoscopy to exclude proximal extension of anal squamous cell carcinoma; and (iii) lack of a fistulous tract lined by squamous cells

Summary

Introduction

Colorectal cancer is the third most common carcinoma in the United States [1]. Lower gastrointestinal cancers are commonly adenocarcinoma in the colon and rectum, whereas squamous cell carcinoma (SCC) is common in the anus. He was treated with 5fluorouracil and mitomycin C with radiation therapy for five weeks with two cycles This was followed by a repeat PET scan in five to eight weeks (Figure 2) that showed complete remission of the hypermetabolic focus in the rectum and peritoneal nodules. The patient had a repeat PET CT scan 20 weeks after complete remission, which showed hypermetabolic right para-aortic, left retroperitoneal, and right retrocrural lymph nodes consistent with malignancy (Figure 3). He is currently on second-line chemotherapy with cisplatin and etoposide

Discussion

Findings

Conclusions

Disclosures