Stromal tumors of gastrointestinal tract include a

variety of primary mesenchymal tumors of the

gastrointestinal tract, such as leiomyoma, leiomyo-

sarcoma, leiomyoblastoma, and schwannoma.1

Schwannomas are rare tumors derived from Sch-

wann cells, which form the neural sheath. Gastro-

intesinal schwannomas are rare and most of them

originate in the stomach or the small intestine. Sch-

wannomas of the colon are extremely rare. Few case

reports have described the occurrence of schwan-

nomas in the colon.1-4

Case Report

Our patient was a 45-year-old woman whose gen-

eral health condition was good before the appearance

of symptoms. She visited our gastrointestinal clinic in

June 2005 complaining of bloody stool with blood

clots and mucus content for 1 week, with several epi-

sodes of mild diarrhea. She denied any abdominal

pain, body weight loss, or recent change in bowel

habit. She also denied any medical or operative his-

tory or family history of cancer. Her vital signs were

normal and physical examination were unremarkable.

Flexible sigmoidoscopy revealed a huge yellow bulg-

ing intra-luminal tumor obstructing the lumen at 50

cm above the anal verge (Fig. 1). A biopsy of the tu-

mor was obtained and pathology showed inflamma-

tory exudates, necrotic debris, acute and chronic in-

flammation, and granulation tissue formation. Though

no malignancy was found in the biopsy specimen, en-

doscopic findings indicated colon cancer, so the pa-

tient was referred to a proctologist for operation. Lab-

oratory tests and other examinations demonstrated

only mild anemia (hemoglobin, 10.0 g/dL). Dou-

J Soc Colon Rectal Surgeon (Taiwan) December 2008

Case Report

Schwannoma of the Colon: Report of a

Case and Review of the Literature

Hsin-Yuan Hung1

Jy-Ming Chiang1

Jinn-Shiun Chen1

Reiping Tang1

Tse-Ching Chen2

1Division of Colon and Rectal Surgery,

Chang Gung Memorial Hospital, Lin-Kou,

Taiwan2Department of Pathology, Chang Gung

Memorial Hospital, Lin-Kou, Taiwan

Key Words

Gastrointestinal schwannoma;

Colon;

Immunohistochemistry

Schwannomas of the colon are extremely rare, and it is necessary to treatthem by radial excision with a wide margin because of their tendency torecur locally and become malignant if inadequately treated. In the presentstudy, we report a rare case of a colonic schwannoma that was success-fully treated by surgical resection in our department. Immunohistochemi-stry revealed that the tumor was positive for S-100 and negative forC-KIT, smooth muscle actin, CD21, CD34, and CD35. The patient wastherefore diagnosed with a schwannoma, not a gastrointestinal stromal tu-mor(GIST). We report the findings of endoscopy, radiology, and pathol-ogy in a patient with colonic schwannoma. The literature on colonicschwannomas has been reviewed.[J Soc Colon Rectal Surgeon (Taiwan) 2008;19:128-132]

Received: September 25, 2008. Accepted: December 31, 2008.

Correspondence to: Dr. Jinn-Shiun Chen, M.D. Division of Colon and Rectal Surgery, Chang Gung Memorial Hospital 199, Tung

Hwa North Road, Taipei, Taiwan. Tel: +886-3-3281200 ext. 2101; Fax: +886-3-3278355.

128

ble-contrast barium examination revealed a huge

ovoid intra-luminal mass in the mid-portion of the de-

scending colon, which resulted in partial obstruction

of the colon. (Fig. 2). Abdominal computed tomogra-

phy (CT) using oral and intravenous contrast agents

revealed a soft tissue mass at the junction of the de-

scending and the sigmoid colon.

No definite paraaortic and pelvic lymphadenoathy

or definite hepatic metastasis was noted (Fig. 3).

In July 2005, the patient underwent an operation

in which a segment about 26 cm-long of the left colon

was resected. On sectioning, a 5*4*3 cm yellowish

white polypoid mass was found. The tumor consis-

tency was elastic, and the tumor originates from a

muscular layer with focal ulcerated overlying mu-

cosa. Microscopic examination of the neoplasm re-

vealed a tumor in the muscular wall composed of in-

terlacing bundles of spindle cells (Fig. 4). Mild nu-

clear pleomorphism and a mitotic activity of 6/50

HPF were noted. Immunohistochemical staining re-

vealed that the tumor cells were positive for S-100

(Fig. 5) and negative for C-KIT, smooth muscle actin,

CD21, CD34, and CD35. The patient was therefore

diagnosed with a colon schwannoma, not a gastroin-

testinal stromal tumor (GIST).

The patient recovered well. She was discharged

on the eighth postoperative day and reqularly fol-

lowed up at the clinic for 2 years; no recurrence was

found.

Discussion

Schwannomas usually present as well-circum-

scribed masses attached to peripheral nerves, cranial

nerves, or spinal nerve roots.5 Schwannomas of the

colon and rectum are extremely rare. Primary schwan-

nomas of the bowel are rare and occur most frequently

Vol. 19, No. 4 Desending Colon Schwannoma 129

Fig. 1. Colonoscopic picture of descending colon Schwan-noma.

Fig. 2. Double-contrast barium examination revealed ahuge ovoid intra-luminal mass in the mid-portion ofthe descending colon (arrow).

Fig. 3. Computed tomography scan revealed a polypoid tu-mor at descending colon.

in the stomach. Colonic schwannoma was first re-

ported by Lamy et al.6 A large number of schwannoma

cases have been reported since 1910. Ito et al re-

viewed 37 cases of schwannomas of the large intestine

in 1996.7

Colonic schwannomas tend to be circumscribed,

but are also non-encapsulated nodular or ovoid mass-

es with a polypoid component. They present as poly-

poid intra-luminal lesions, and the overlying mucosa

may have ulcerations. The tumor specimen obtained

by forceps biopsy is not always sufficient for his-

tological diagnosis. In our patient, the biopsy showed

ulceration with granulation tissue. The patient pre-

sented with symptoms, including abdominal pain,

bowel obstruction, and rectal bleeding.8

Colonic schwannomas are slow-growing tumors

and are usually solitary. These lesions are character-

ized by a peripheral lymphoid cuff, which may con-

tain germinal centers.3 Routine hematoxylin and eosin

staining does not enable differentiation between ne-

urogenic and myogenic tumors. Immunohistochemi-

cal staining is a new reliable technique for making a

correct differential diagnosis. In our patient, the tumor

cells were positive for S-100 protein and negative for

CD34 and smooth muscle actin. Gastrointestinal sch-

wannomas are reported to be commonly associated

with a diffuse S-100 protein reaction and peri-tumoral

lymph follicles.9

Most schwannomas are benign and symptomatic,

but the possibility of malignant degeneration does ex-

ist and is directly related to the tumor dimensions.

Radical surgical treatment is the gold standard in all

cases. The role of chemotherapy and radiotherapy in

treating schwannomas remains uncertain.10,11

In our patient, the tumor size was large (5 cm) and

the mitosis count was 6 per 50 high-power fields;

therefore, we diagnosed this tumor as having high ma-

lignancy potential. Since histological criteria for de-

fining the grade of malignancy of gastrointestinal

schwannomas have not yet been determined, and still

their metastatic potential is not known, careful obser-

vation of the patient’s postoperative course should be

necessary.

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