Adenosquamous and squamous carcinoma of the colon and upper rectum: a clinical and histopathologic study

Squamous and adenosquamous carcinoma of the colon and proximal rectum are rare neoplasms in which the clinicopathologic behavior and the most appropriate management are unknown. The purpose of this study was to review the histology and clinical course of the largest series of cases ever reported from a single center on this rare condition.

The Mayo Clinic tissue registry was searched for all primary cases of squamous and adenosquamous carcinoma of the colon or rectum proximal to 8 cm from the dentate and presenting before December 31, 1992. Of the 52 identified cases there was adequate histologic material for review in 44 cases. These cases were divided into pure squamous-cell carcinoma (n = 11), mixed adenosquamous carcinoma (n = 31), and adenocarcinoma with benign-appearing squamous metaplasia (adenoacanthoma; n = 2). Squamous-cell carcinomas were examined for evidence of human papilloma virus by in situ hybridization. A retrospective review of medical records was undertaken in all 52 cases with respect to predisposing factors, clinicopathologic behavior, prognostic features, and treatment with adjuvant therapy.

The charts of 52 patients (20 females), with a mean age of 58.6 (range, 19-90) years, were reviewed. Right-sided lesions were the most common (43 percent). Metastatic disease was evident at presentation in 49 percent of patients, the most common sites in order being liver, peritoneal, and lung. The five-year overall survival rate was 34 percent, Stage I to III disease had a 65 percent five-year survival rate, and Stage IV mean survival time was 8.5 months. For node-positive and node-negative disease, 23 and 85 percent, respectively, survived five years. There was no evidence of human papilloma virus in the six squamous-cell carcinomas examined.

Squamous and adenosquamous carcinomas of the colon and rectum are rare neoplasms. Although a poor prognosis can be expected for node-positive disease, patients with negative nodes do generally the same as patients with adenocarcinoma histology. Based on advances made with multimodality therapy of squamous-cell cancer of the anus and adenocarcinoma of the rectum, further studies should define the role of postoperative therapies for these lesions.