Introduction
Sarcomatoid carcinoma is described as pseudosarcomatous carcinoma, carcinosarcoma, spindle cell carcinoma or carcinoma with mesenchymal stroma in various studies.1 With uncertain histogenesis, this rare tumour is composed of carcinoma and mesenchymal cells and discovered at various locations like head and neck respiratory tract, male and female genital tracts and gastrointestinal tract.2, 3 In GIT, oesophagus and oropharynx are the common sites with colon being a rare site.4 Many of these tumours in colon may be diagnosed as GIST, Malignant fibrous histiocytoma (MFH), or leiomyosarcoma. Immunohistochemical staining with cytokeratin and vimentin is helpful in the diagnosis of Sarcomatoid carcinoma of Colon.
We report a case of a 65 years old lady, a known case of Non-Small Cell Carcinoma of Lung on treatment, who presented with pain abdomen. On examination, she had tender abdomen. CECT revealed colonic intussusception with large colonic mass causing obstruction. The patient was put up for right hemicolectomy and the specimen was sent for histopathological examination.
Gross Examination
A right hemicolectomy specimen was received measuring 30 cm in length. On cut open, a polypoid mass measuring 9 x 6.5 x 3 cm was noted in the ascending colon, 16 cm from the proximal and 4 cm from the distal resection margins. Cut surface was solid and whitish.
Microscopy
Sections from the polypoidal tumour was composed of pleomorphic round to epithelioid spindly cells. Mitoses of 12-15/ HPF was noted. Lymphovascular and perineural invasion were not seen.
Immunohistochemistry
On IHC, tumour cells were positive for both vimentin (Fig.5) and Pan-cytokeratin (Figure 4).
Figure 1
Gross appearance of the tumour showing polypoidal grey white mass as part of intussusception
So, histopathology and IHC confirmed the diagnosis of sarcomatoid carcinoma of colon.
Discussion
Sarcomatoid carcinoma of colon was first described by Weidner and Zekan in 1986. 5 It is an aggressive, rare tumour and associated with poor prognosis. Less than 50 cases have been reported in literature till date. Due to limited studies on this tumour, the prognostic factors are yet to be properly elucidated.
Various studies have tried to explain the pathogenesis of this tumour. Study done by Gentile et al 6 had described the progression of tumour from tubulovillous adenoma to sarcomatoid carcinoma. Study done by Delahunt at al 3 linked the accumulation of p53 proteins with the conversion of carcinoma to sarcomatoid tissue.
Histopathologically, the epithelial cells undergo epithelial-mesenchymal transition and appear spindle shaped.
Lymph nodal and distant metastases have been described for the carcinomatous component and is rare for the sarcomatous component. 7 As this is a rare and aggressive tumour with poor prognosis, specific treatment guidelines are limited. Radical surgery, adjuvant chemotherapy and close follow-up is the accepted norm. 8, 9
In this case, the patient has undergone surgery and is now on adjuvant chemotherapy.
Conclusion
More studies on this rare aggressive tumour with poor prognosis needs to be done to find out the epidemiological and prognostic factors. Immunohistochemistry plays a pivotal role in the diagnosis of such tumours with spindle cell morphology.
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