S1811 A Rare Case of Synchronous Squamous Cell Tumors of the Rectum: Diagnosis and Management

Abstract

INTRODUCTION: Colorectal squamous cell carcinoma (SCC) is an extremely rare form of colon cancer, accounting for 0.1–0.2% of the cases. It has a female predominance, with a mean age of 57 years old at diagnosis. It is often diagnosed at an advanced stage. We present a case of two simultaneous SCC tumors of the rectum which were managed successfully with multidisciplinary approach. CASE DESCRIPTION/METHODS: A 65 year old female with remote history of left breast ductal carcinoma in situ, in remission after lumpectomy and adjuvant chemoradiation therapy several years ago, presented with intermittent hematochezia. She denied having any constitutional symptoms. Her previous colonoscopy was eight years prior and was unremarkable. There was no family history of gastrointestinal cancer. She rarely drank alcohol and did not smoke cigarettes. During rectal exam, a large mass was palpated in the rectum, without any palpable anal abnormalities. Labs showed normal CBC, LFTs and renal function. She underwent a colonoscopy which revealed an exophytic and friable 4 cm mass in the distal rectum. A separate subepithelial mass was seen at the rectosigmoid junction, with ulcerated mucosa overlying the lesion. The intervening rectum between the 2 distinct masses and the portion of the rectum distal to the rectal mass were both normal. Separate biopsies were taken of the two masses, and pathology revealed invasive, moderately differentiated squamous cell carcinoma with HPV positivity (Image 1). Imaging for staging did not reveal any metastases. The patient received neoadjuvant radiation and chemotherapy (Mitomycin C and 5-Fluorouracil). Post-treatment abdominal imaging showed significant response to therapy (Image 2). Subsequently, the patient underwent a laparoscopic hand assisted proctosigmoidectomy with colonic pouch anal anastomosis and diverting loop ileostomy. Pathology showed complete resolution of tumor at primary sites while carcinoma cells were found in one of the resected lymph nodes (Image 3). DISCUSSION: Colorectal SCC occurs mostly in the distal half of the colon, mainly at the rectosigmoid junction. While isolated colorectal SCCs are rare, our case is even more unique given the presence of synchronous colorectal SCC tumors. HPV infection is associated with colorectal SSC in past literature. To decrease the risk of SCC recurrence, neoadjuvant chemoradiation followed by surgical resection is the mainstay of treatment while recent evidence suggests that chemoradiation alone may be definitive therapy in some cases.Figure 1.: Colonoscopy showing submucosal mass with overlying ulcerated mucosa (arrow) at the rectosigmoid junction (A) and exophytic, friable mass seen in the distal rectum (B). Rectal mass biopsy H & E stain (20X) showing full thickness squamous atypia with lack of maturation consistent with squamous cell carcinoma (C) while diffuse nuclear p40 stain positivity (10X) supporting squamous origin (D) and strong p16 staining (10X) indicative of HPV-associated squamous cell carcinoma (E).Figure 2.: MRI abdomen showing submucosal mass (see arrow) at rectosigmoid junction with compression of lumen (A) and intraluminal mass (see arrow) in distal rectum (B). After chemotherapy and radiation, the mass at rectosigmoid has reduced to scar tissue with T2 hypointensity (C) while mass in distal rectum has completely resolved (D).Figure 3.: H & E stain (20X) showing no residual tumor identified in treated colon of patient with history of squamous cell carcinoma in (A) while treatment effect shown with numerous macrophages, few multinucleated giant cells (black arrow), lymphocytes and small vessel with hyaline changes (blue arrow) in B, and CD68 stain highlights macrophages within the area of treatment response (C). H & E stain (20X) showing lymph node with metastatic carcinoma showing treatment effect and viable tumor cells (arrows) within necrotic debris in lymph node in (E) while CK AE1/3 immunohistochemistry stain (20X) highlighting/confirming metastatic carcinoma with both viable tumor cells and necrotic cells expressing pancytokeratin.