A 66-year-old female presented with pancytopenia, hypotension,
and a diffuse purpuritic skin rash on her face and both lower
extremities (figure 1). She was diagnosed with vasculitis, and
steroidal therapy was initiated. A CT scan was obtained which
demonstrated a calcified mesenteric mass (figure 2) with
surrounding mesenteric infiltration. Wall thickening of several
adjacent bowel loops was present. The liver was normal. Selective
injection of the superior mesenteric artery revealed tandem,
segmental stenoses of the distal ileal branches with thrombosis of
the associated draining veins (figure 3). The mass was biopsied and
resected. Postoperatively, multiple skin grafts were placed and the
patient was discharged. What is the diagnosis?
At surgery, the patient's distal small bowel and mesentery
were amalgamated and inseparable. Pathology of the mesenteric mass
revealed a carcinoid tumor.
Ninety percent of carcinoid tumors occur in the GI tract.
These account for 25% of all small bowel tumors and arise from
enterochromaffin cells at the base of the crypts of Lieberkuhn. The
most common location of GI carcinoid tumors is in the appendix
(50%), followed by the small bowel (20% found in the ilium, which
is ten times more common than in the jejunum), rectum (15%), and
stomach and duodenum (5% each).
Appendiceal tumors grow slowly and rarely metastasize. It has
been suggested that these patients frequently exhibit symptoms of
appendicitis before spread occurs, or the diagnosis is made
incidentally when the appendix is removed during cesarean section,
hysterectomy, or cholecystectomy. Eleven percent of appendiceal
carcinoids invade the mesoappendix, but metastases remain unlikely.
Ileal carcinoids are much more aggressive and when they grow larger
than 2 cm, metastases are frequent. Over 75% of patients with
symptomatic spread have a midgut origin.
Carcinoid tumors are of endocrine origin and are classified in
the same category of tumor as pheochromocytoma, medullary carcinoma
of the thyroid, and islet cell tumor of the pancreas.
Duodenal carcinoids have been associated with multiple endocrine
Thirty to 40% of carcinoid tumors have other synchronous or
Carcinoid syndrome is a constellation of clinical findings
related to hormones (most commonly, 5-hydroxytryptamine, or
serotonin) secreted by the tumor. Symptoms of carcinoid syndrome
include flushing, diarrhea, vasomotor instability, endocardial
fibroelastosis, and bronchoconstriction.
In normal individuals, 1% of dietary tryptophan is converted
to serotonin. In the setting of carcinoid syndrome, however, up to
70% of dietary tryptophan may be diverted to this pathway, leaving
insufficient quantities of tryptophan available to generate niacin.
These patients (such as ours) may become overtly niacin deficient
and may present with the characteristic skin changes of pellagra.
Overall, 7% of patients with carcinoid syndrome contract pellagra.
The most common skin change is the formation of multiple
telangiectasias, which occurs in 25% of afflicted individuals.
These are of uncertain origin.
Serotonin metabolized by monoamine oxidase and the breakdown
product, 5-hydroxyindoleacetic acid (5-HIAA), is excreted in the
urine. Excess 5-HIAA in the urine is an indicator of carcinoid
syndrome. Although serotonin is responsible for the majority of
symptoms from carcinoid syndrome, other substrates, including
kallikrein and bradykinin, may cause parts of the symptom complex.
Radiographically, ileal carcinoids usually are submucosal and
are most commonly found within the last two feet of the ileum. Even
when greater than 2 cm in size, these lesions may be quite
difficult to identify at barium studies with the typical redundancy
of the distal small bowel. Systematic fluoroscopic compression is
essential to identify these lesions. Approximately 30% are
The desmoplastic response of the mesentery from the locally high
levels of serotonin leads to angulation and kinking of the bowel,
as well as matting of multiple loops. On computed tomography it is
common to see a focal, calcified mesenteric mass surrounded by
thickened mesentery.The liver is frequently the site of multiple
hypoattenuating lesions which may appear hyperdense during the
arterial phase of injection with helical imaging. Other processes
that present with similar mesenteric findings include Hodgkin's
disease, extensive radiation damage, and advanced metastatic
disease from other processes.
At angiography, the kinking and retraction of the small bowel
and mesentery leads to a "sunburst" appearance. The tumor may be
identified as a hypervascular mass. Arterial branch stenoses are
common due to an elastic vascular sclerosis secondary to the
elevated serotonin levels. These stenoses may lead to mesenteric
ischemia. Venous return is often abnormal or interrupted. No other
vasculitic changes are common.
Even in patients with metastatic symptomatic midgut
carcinoids, the disease progresses slowly, with patients surviving
an average of 3.2 years after diagnosis of liver metastases.
The symptoms from carcinoid syndrome have a higher morbidity and
mortality than does the tumor itself.
Chemoembolization of the hepatic arteries supplying liver
metastases is a useful tool which has been shown in one study to
decrease serotonin levels
while increasing patient life span by 5.2 years.