Uncommon Colorectal Neoplasms

 

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The diagnosis and management of uncommon tumors of the pelvis, rectum, and colon are difficult because of the rarity of many of these disease entities. As a result, there is often a delay in the diagnosis and treatment of these lesions. Pathology of pelvis and perineum is often the bane of the general surgeon or practitioner, but the ability of colon and rectal surgeons to manage rare or unusual tumors of the pelvis and perineum readily and appropriately distinguishes their expertise.

Given the wide diversity of histology found in the pelvis, there is a great variety in the different types of tumors that occur in this region. As mentioned, many of these tumors are quite rare, and much of our knowledge comes from retrospective case series. This has not allowed significant progress in understanding their pathophysiology and developing optimal treatment schemes for them. On the other hand, our understanding of lesions such as gastrointestinal stromal tumors and anal intraepithelial neoplasia is evolving at a fairly rapid rate. The goal of this issue of Clinics in Colon and Rectal Surgery is to provide an accurate and concise account of the literature for many of the rarer tumors of the pelvis and to update the reader with the latest in their evolving management.

Drs. Philip Chung and Steven Hunt begin the issue with a review of carcinoid tumors. They discuss the diagnosis, surgical management, and evolving advances in the adjuvant therapy used to treat neuroendocrine tumors.

Next, colorectal lymphomas are discussed by Drs. Frank Quayle and Jennifer Lowney. The gastrointestinal tract represents the most common extranodal site for lymphoma to occur. Chemotherapy is the preferred therapeutic modality, and surgery is typically reserved for complications of the disease. However, given the rarity of primary gastrointestinal lymphoma, there is some uncertainty, depending on which literature is reviewed, regarding its optimal management.

Epidermoid tumors of the anus is presented by Drs. Bruce Robb and Matthew Mutch. For better understanding of these tumors, there have been changes in their classifications, which are discussed. The evolution and current role of chemoradiation therapy as definitive therapy and surgery as palliation or salvage therapy are discussed.

Retrorectal tumors are addressed by Drs. Sean Glasgow and David Dietz. These tumors are rare and often difficult to diagnose. The review covers the diagnosis, imaging, preoperative planning, and surgical approach to the wide variety of benign and malignant presacral tumors.

Drs. Rishindra Reddy and James Fleshman discuss gastrointestinal stromal tumors (GISTs). There have been significant advances in our understanding and management of these tumors. The identification of tumor suppressor gene c-kit as the underlying mechanism for the development of GISTs has greatly advanced our understanding of the mechanisms of tumorigenesis. It has also led to the development of the “targeted” chemotherapeutic agent imatinib mesylate, a tyrosine kinase inhibitor.

Drs. Marc Singer and Matthew Mutch review the management of anal melanoma. This lesion is considered a great masquerader because its signs, symptoms, and appearance often mimic those of common benign diseases of the anus. Unfortunately, it is a highly lethal tumor and few advances have been made over the past several decades. The article addresses how to avoid delays in diagnosis and the management issues of wide local excision versus abdominoperineal resection.

The increasingly difficult problem of anal intraepithelial neoplasia (AIN) and other benign lesions of the perineum are covered by Drs. Aalok Sahai and Ira Kodner. In the era of human immunodeficiency virus, the incidence of AIN has exploded. In many respects, this represents the same disease that occurs in immunocompetent patients, but its natural history and the risk of malignant degeneration in the immunocompromised population have created a much more complicated disease process. The authors address the evolution in the demographics, management, and surveillance of AIN in both immunocompetent and immunocompromised patients.

The last topic, vascular tumors of the pelvis, is covered by Drs. Marcus Tan and Matthew Mutch. Hemangiomas and other vascular lesions are unusual causes of lower gastrointestinal bleeding, which, if left unrecognized, can lead to life-threatening hemorrhage. They present the essentials for a timely diagnosis and treatment plan.

I had great pleasure putting together this issue of Clinics in Colon and Rectal Surgery. It is my hope that the reader finds it informative and enjoyable to read.

Matthew G MutchM.D. 

Section of Colon and Rectal Surgery, Department of Surgery, Washington University School of Medicine

660 S. Euclid Ave., Box 8109, St. Louis, MO 63110-1010

Email: mutchm@wudosis.wustl.edu