British Journal of Radiology (2005) 78, 255-256
© 2005 British Institute of Radiology
doi: 10.1259/bjr/36083619
Small cell carcinoma of the colon: barium study and CT findings
H C Kim, MD1,
S I Park, MD1,
S J Park, MD2,
H C Shin, MD1,
M-H Oh, MD3,
H H Kim, MD1,
W K Bae, MD1 and
I Y Kim, MD1
Department of 1 Diagnostic Radiology and 3 Pathology, Soonchunhyang University, Cheonan Hospital, 23–20 Bongmyung-dong, Cheonan, Chungcheongnam-do, 330-721 and 2 Department of Diagnostic Radiology, College of Medicine, Soonchunhyang University, Bucheon Hospital, 1174 Jung-dong, Wonmi-gu, Bucheon, Gyeonggi-do, 420-021, Republic of Korea
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Abstract
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Extrapulmonary small cell carcinoma is a rare neoplasm. It is an aggressive malignant tumour characterized by rapid local progression and early metastasis. We report a case of small cell carcinoma arising in the transverse colon in a 34-year-old man who presented with epigastric pain. On CT, a poorly enhancing bulky mass encircling the transverse colon with extensive regional lymph node metastases was observed. A segmental annular narrowing with thick interhaustral folds of the transverse colon was found by barium enema examination. This is the first report of barium study and CT findings of extrapulmonary small cell carcinoma of the colon.
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Introduction
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Extrapulmonary small cell carcinoma is a rare malignant condition that can arise from various organs, such as the salivary gland, pharynx, oesophagus, stomach, small bowel, colorectum, gallbladder, uterus, kidney and skin [1, 2]. This neoplasm manifests highly aggressive behaviour and the prognosis is generally poor, especially when involving the gastrointestinal tract [1–3]. Small cell carcinoma of the colon is rare, and constitutes about 1.5% of all colon cancers [4]. To our knowledge, the radiological findings regarding small cell carcinoma of the colon have not been previously described in the English literature. We present the barium enema and CT findings of a case of small cell carcinoma of the colon.
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Case report
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A 34-year-old man was hospitalized due to epigastric pain. Physical examination revealed a palpable mass in left upper abdomen. Chest radiography showed no pathological findings. An abdominal CT scan was performed on an eight-channel multislice helical CT scanner (LightSpeed Ultra; General Electric, Milwaukee, WI). It revealed a poorly enhancing mass encircling the transverse colon (Figure 1a
) and extensive adjacent lymph node metastasis (Figure 1b). Barium enema examination showed mild annular narrowing with thickening of interhaustral folds in the transverse colon (Figure 2). The proximal and distal margins of the lesion showed gradual tapering without shouldering. Colonoscopy showed a semicircular ulcerating and fungating mass in the transverse colon. Microscopic examination obtained from colonoscopic biopsy showed that the mass is composed of small cells with hyperchromatic nuclei, coarse chromatin, inconspicuous nucleoli and little cytoplasm. Immunohistochemical examination revealed diffuse positivity for CD56, synaptophysin, and neuron-specific enolase, and negativity for cytokeratin, leukocyte common antigen, CD3 and CD20, which was consistent with small cell carcinoma. The patient is being treated by systemic chemotherapy.
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Figure 1. Post contrast enhanced CT images of the small cell carcinoma of the colon. (a) Axial CT image shows bulky poorly enhancing mass (black arrows) encircling the transverse colon (open arrows). (b) Axial CT image obtained 55 mm above the mass shows extensive metastatic lymph node enlargement (white arrows) in the both para-aortic areas and along the mesenteric root.
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Figure 2. Barium enema examination shows mild annular narrowing of the transverse colon with thick interhaustral folds due to circumferential invasion by the small cell carcinoma. The proximal and distal margins of the lesion (arrows) are gradually tapered.
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Discussion
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Extrapulmonary small cell carcinoma has been understood as a distinct disease entity with biological behaviour and prognosis different from those of other carcinomas of a given site [1, 2]. The pathological features of extrapulmonary small cell carcinoma are similar to those of pulmonary small cell carcinoma [5]. They have small neoplastic cells with a markedly hyperchromatic nucleus and scanty cytoplasm. They frequently showed neuroendocrine differentiation by immunohistochemical staining for neuron-specific enolase, chromogranin and synaptophysin [3].
The diagnosis of extrapulmonary small cell carcinoma of the colon should be made only when the possibility of metastasis from a tumour arising in the lung has been excluded. Although a chest CT scan was not performed in our case, chest radiographs were normal at presentation and remained normal over a 6 month follow up period.
Small cell carcinoma is rare in the colon or rectum, accounting for about 1.5% of all colorectal carcinomas [4]. In a review of previous reports on small cell carcinoma of the colon, radiological findings have not been described in the English literature. Our case showed a poorly enhancing bulky exophytic mass encircling the transverse colon on CT. The barium enema showed mild annular narrowing and thick interhaustral folds without overhanging edges, which were different from typical findings seen in ordinary annular colonic adenocarcinomas. Small cell carcinoma of the colon is a neuroendocrine tumour that can originate from the mucosa as well as the submucosa, and the barium enema appearances of our case were more suggestive of a submucosal lesion invading the mucosa than a mucosal lesion. However, the precise site of origin of the tumour could not be identified histologically because the pathological specimen was only obtained from colonoscopic biopsy, and not from a gross specimen obtained at operation. Additionally, our case could not easily be differentiated from circumferential involvement of the transverse colon by lymphoma from the CT and barium enema findings. Because colonic lymphomas are relatively less common and show diverse imaging features [7], specific differential imaging features between colonic lymphoma involvement and our case could not be found.
In conclusion, we present the barium study and CT findings of a very rare case of extrapulmonary small cell carcinoma of the colon.
Received for publication August 5, 2004.
Revision received October 20, 2004.
Accepted for publication November 25, 2004.
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References
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Abstract
Introduction
