Primary Adenocarcinoma of Small Intestine: A Case Report

 

Article by:

M. Shaikh

R.G.W. Pinto

 

 

Abstract

Although the small intestine contributes to 75% of mucosal surface area of the gastrointestinal (GI) tract, malignancies of the large intestine are fifty times more numerous and the small intestine is the site of only 1% of all GI tumors. Furthermore, adenocarcinomas of the small bowel are most frequent in the duodenum and are increasingly less common at more distant sites of the small intestine.[1]

 

Introduction:

The small intestine with its three parts; the duodenum, jejunum, and ileum, represents the longest part of the digestive tract accounting for 75% of the length (about 6 metres long and 4 times the length of the large intestine) and 90% of the absorptive surface of the GI tract.[2]

Malignant tumors of the small intestine are rare all over the world with a global incidence of less than 1.0 per 100,000 population.[3] Cancers of the small intestine account for only 0.42% of total cancer cases and 2-3% of cancers of digestive system in the United States.[4] Owing to the rarity of its occurrence, there is limited data in Indian literature.

There are 4 major histological subtypes  of  small intestinal malignancies which are adenocarcinoma, malignant carcinoid, lymphoma and leiomyosarcoma; adenocarcinoma being the commonest histological type.[5]

Here we present a case of adenocarcinoma of small bowel with extensive metastasis to the peritoneum, forming serosal nodules in the large bowel and consequently causing ischemic perforation of a segment of large bowel.

 

Case report:

A 75-year-old female, ex-smoker  (beedi)  for 20  years,  presented  with  a  chief  complaint  of  moderate  to  high  grade  fever  for  20  days, vomiting dark brown-black vomitus for 2 days, loose black tarry stools for 2 days. Patient was pale, with decreased bilateral breath sounds. There was bilateral massive pleural effusion, perforation of large bowel and peritonitis.

Exploratory laparotomy revealed a 3 x 3 cm perforation in the splenic flexure of the colon and multiple aphthoid ulcers in the transverse colon. Multiple peritoneal deposits and pelvic seedlings were observed. The medial surface of spleen was sloughed off. There was a growth noted in the mesentery of the small bowel 60 cm distal to duodeno jejunal flexure which was believed by the surgeon to be a metastasis from adenocarcinoma of large bowel. Resection of large bowel segment, resection anastomosis of the jejunal segment with the growth and, splenectomy was done and specimens were sent for histopathology.

 

GROSS  EXAMINATION:

The segment of jejunum showed a vertically oval ulcer 1 x 1.5 cm located at the mesenteric border (Figure 1). Cut section through the ulcer showed a grayish-white growth infiltrating the mesentery (Figure 2).

TC-July2017-024 - Segment of jejunum with the growth seen TC-July2017-025 - The growth is seen to infiltrate the mesentery

The large bowel segment measuring 22 cm in length showed a perforation measuring 3 x 3 cm. Ten periserosal nodules were isolated from the large bowel.

 

MICROSCOPY:

Sections from the growth in the jejunum showed moderately differentiated adenocarcinoma infiltrating the serosa (Figures 3 and 4).

TC-July2017-026 - Hematoxylin & Eosin (H&E) TC-July2017-027 - H&E section x 40 X view of moderately differentiated adenocarcinoma

Sections from the perforation in the large bowel showed acute inflammation, perforation, hemorrhage and ischemic necrosis. There was no evidence of malignancy. Sections from the periserosal nodules showed evidence of metastasis from moderately differentiated adenocarcinoma. Sections from spleen showed extensive necrosis.

 

Discussion:

Malignant tumors of the small intestine are amongst the rarest of GI malignancies. Several theories have been postulated to explain why the low incidence of malignant tumors at this site such as, the presence of large volumes of alkaline fluid in the small bowel, the presence of various enzymes and high IgA levels, causing dilution and detoxification of potential carcinogens and the prevention of prolonged contact of such carcinogens with the mucosa. In addition, the small intestine has a very limited number of bacteria that can transform potential procarcinogens to carcinogens.[5]

In general, adenocarcinoma of the small intestine predominates in males as compared to females (male to female ratio of approximately 1.4:1),[6,7] and has a peak incidence in the 7th decade. The most common site is periampullary duodenum; adenocarcinomas in the jejunum and  ileum  are  rare.[8,9]

Significant risk factors for adenocarcinoma of the small intestine include Crohn’s disease, celiac disease, Lynch syndrome and familial adenomatosus polyposis (FAP).[10,11] Patients with Peutz-Jeughers syndrome, juvenile polyposis and MUTYH-associated polyposis are also at an increased risk. Adenocarcinoma rarely develops in ileostomies and ileal pouches after colorectal surgeries. Small bowel adenocarcinomas are usually asymptomatic in the initial stages; most patients therefore present with advanced tumors when bowel obstruction occurs. The most common symptoms include abdominal pain, weight loss, vomiting and occult gastrointestinal bleeding.[9]

The typical gross appearance, histological features and immunochemistry findings are discussed below.

 

GROSS:

Duodenal adenocarcinoma is usually relatively well circumscribed and have a polypoidal/ papillary configuration and central ulceration whereas jejunal and ileal tumors most often show circumferential annular involvement with extensive ulceration. Ileal adenocarcinoma may mimic Crohn’s disease. Multifocality and lack of mucosal component should raise the possibility of a metastasis.[12]

 

HISTOLOGY:

These are usually moderately differentiated adenocarcinomas associated with a mucinous component.[12]

 

IMMUNOHISTOCHEMISTRY:

Adenocarcinoma of the small intestine most often express CK 7 (30-50% of tumors) and less often CK-20 (only around 60% of tumors).[13,14] CDX-2 is usually positive but often with a heterogeneous staining pattern including areas with only weak staining/without expression.[13]

 

TC-July2017-028 - Authors Pg32

 

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