|Year : 2015 | Volume
| Issue : 4 | Page : 1035
Diagnosis of leiomyosarcoma of colon
P Kiran1, PM Shiny2, KS Dhanya1, KP Aravindan2
1 Department of Radiotherapy, Government Medical College Calicut, Kozhikode, Kerala, India
2 Department of Pathology, Government Medical College Calicut, Kozhikode, Kerala, India
|Date of Web Publication||15-Feb-2016|
Ushus Bhavan, Mayithara PO, Cherthala - 688539, Kerala
Source of Support: None, Conflict of Interest: None
Leiomyosarcomas of colon are rare tumors accounting for less than 1% of cases which are often misdiagnosed and confused with gastrointestinal stromal tumor (GIST). We report a case of 54-year-old male presenting with abdominal pain with computer tomography (CT) showing a retroperitoneal mass. He underwent laparotomy and surgical excision of mass was done. On pathological examination, microscopy was suggestive of GIST, but immunohistochemistry was positive for desmin and ultimately this case was diagnosed as leiomyosarcoma.
Keywords: Gastrointestinal stromal tumor, GIST of intestine, leiomyosarcoma colon
|How to cite this article:|
Kiran P, Shiny P M, Dhanya K S, Aravindan K P. Diagnosis of leiomyosarcoma of colon. J Can Res Ther 2015;11:1035
| > Introduction|| |
Incidence of leiomyosarcomas of colon is very low (1:100,000). These tumors usually present as abdominal pain and sometimes as lower gastrointestinal (GI) hemorrhage. This is essentially a pathological diagnosis with hematoxylin and eosin staining having a similar appearance to that of GI stromal tumor (GIST), but with a different immunohistochemistry profile.
| > Case report|| |
A 54-year-old male presented with right iliac fossa pain of 2 month's duration. Clinical examination revealed a mass in the pelvis extending to right iliac fossa. Routine blood investigations were noncontributory and with normal tumor markers. Colonoscopy and upper GI endoscopy were normal. Computed tomography (CT) of abdomen showed a retroperitoneal tumor of size 8.5 × 9.7 × 9.9 cm. The tumor was well-defined, lobulated soft tissue mass with heterogeneous contrast enhancement in the right side of pelvis extending to right iliac fossa. There was no CT evidence of tumor invasion to adjacent organs, ureteric obstruction, or nodal involvement [Figure 1] and [Figure 2]. He underwent exploratory laparotomy and a mass attached to serosa of colon of size 13 × 6.5 cm was identified.
|Figure 1: Coronal section of CT scan showing heterogeneous contrast enhanced mass arising from the serosa of cecum and ascending colon without infiltration of the surrounding structures and luminal extension. CT suggestive of GIST|
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|Figure 2: Axial section of CT scan showing heterogeneous contrast enhanced mass arising from the serosa of cecum and ascending colon without infiltration of the surrounding structures and luminal extension|
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Histopathological examination revealed a solid grey white nodular mass of size 13 × 11 × 6.5 cm in the serosa of ascending colon and cecum extending to ileum. Overlying mucosa was stretched over the tumor. Resected margins of the tumor were free. Microscopy showed a cellular neoplasm with spindle cells arranged in interlacing fascicular pattern [Figure 3]. There was moderate degree of cellular atypia. Mitotic activity ranged from 10 to 12/10 high power field. With provisional diagnosis of GIST, immunohistochemistry was done. Tumor cells were strongly positive for desmin and vimentin and focally positive for smoothmuscle actin [Figure 4] and [Figure 5]. Tumor cells were negative for DOG1,CD34,CD117 [Figure 6] and [Figure 7]. Diagnosis of Grade III leiomyosarcoma was made. Omentum shows infiltration by tumor cells. There was no lymph node metastasis. Resected margins were free.
After surgical excision, patient had adjuvant chemotherapy with ifosfamide and doxorubicin for six cycles and was on follow-up. After an event-free period of 6 months, patient was evaluated with CT of the abdomen which showed a local recurrence of the lesion at the anastomotic site and underwent revision surgery and he is on follow-up now.
|Figure 3: Eosin and haematoxylene-Low power view showing cellular neoplasm with spindle cells arranged in interlacing fascicular pattern with necrosis|
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| > Discussion|| |
Leiomyosarcoma of colon is an infrequent diagnosis usually occurring in males in their middle age.  GISTs are the most common mesenchymal tumors of the GI tract, representing 1-3% of GImalignancies. They are typically defined as tumors whose behavior is driven by mutations in the Kit gene or PDGFRA gene.
Due to increased incidence and histological similarity with GIST, in past leiomyosarcoma, were misdiagnosed as GIST. Immunohistochemistry is the crux of the diagnosis. GIST stains positive for CD 34 and C-kit (CD 117) andstains negative for desmin in contrast to leiomyosarcomas which are positive for desmin and negative for SMA, CD117, CD34, and DOG1. 
Size and grade of leiomyosarcomas determines the survival.  The most important prognostic factor for distant metastasis and survival is grade. For low-grade tumors, the risk of distant metastases at 5 years is <10% compared with almost 50% for high-grade tumors. Tumor size and depth are also prognostic factors with respect to distant metastasis. Presence of tumor cells at the surgical margin and inadequate surgical excision are the most important adverse risk factors for local recurrence. 
In contrast to GIST which is curable with surgery followed by imatinib (in intermediate and high risk patients), leiomyosarcomasbehave aggressively requiring radical excision of tumor followed by intensive cytotoxic chemotherapy regimens. Radiotherapy has only a limited role. Specific guidelines for follow-up are lacking due to rarity of the tumor. In this case as evidenced by the aggressive nature of the tumor, patient had a local recurrence after 6 months.
| > Conclusion|| |
Immunohistochemistry is unavoidable tool in diagnosis of leiomyosarcoma and should be considered in GIST, particularly in unusual sites.
| > References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]