Macroscopically the resected 18 cm colorectal specimen showed an ulcero-fungating mass 6x5 cm in diameter which obstructed the lumen almost completely. There were 2 polyps in the vicinity of the tumor which were 1,5 and 0,5 cm in diameter and 41 lymph nodes were resected from the meso.

Histologically the tumor was composed of a mixture of carcinomatous and sarcomatous areas (Figure 1). The carcinomatous component was a moderately differentiated adenocarcinoma with intracytoplasmic and luminal mucin production in some areas. Sarcomatous component was composed of anaplastic giant cells with strangely shaped nuclei showing bizarre mitoses but there was also a population of smaller spindled cells which were arranged in short fascicular and haphazard pattern (Figure 2).

Fig 1: Carcinomatous and sarcomatous areas of the tumor (H&E;, x110)

Fig 2: Sarcomatous areas with anaplastic giant cells, (H&E;, x220)

Immunohistochemical studies showed strong positivity for cytokeratin and EMA in adenocarcinomatous areas and also in many of the bizarre giant cells of the sarcomatous areas (Figure 3). These sarcomatous areas were mainly vimentin positive but smooth muscle actin and myoglobin negative.

Fig 3: Strong positivity for keratin in carsinomatous areas and also in many cells of the sarcomatous areas (Keratin, x220)

The two polyps found were adenomatous and the larger one showed focal malignant transformation.

The two lymph nodes out of 41 examined lymph nodes were metastatic and interestingly it was sarcomatous in one lymph node and carcinomatous in the other.

The postoperative course was uneventful and the patient received 3 cycles of chemotherapy with local radiotherapy. He is alive with no evidence of disease 4 months after surgery.

The histogenesis of sarcomatoid carcinomas is uncertain and various hypothesis have been proposed to explain the biphasic nature of these tumors. One is collision theory of independent neoplastic growths from multipotent stem cell, epithelial to mesenchymal conversion by epithelial-stromal reaction and the other is the combination of the two [1,2,4]. As we could demonstrate the epithelial nature of the sarcomatous tumor cells immunohistochemically with cytokeratin and EMA positivity in our patient, this finding supports the dedifferentiation of carcinoma cells which means epithelial to mesenchymal conversion.

These tumors when located in the upper aerodigestive tract including esophagus and stomach have polypoid architecture and can be diagnosed early and usually have a relatively favorable prognosis. But sarcomatoid carcinomas of the lower intestinal tract have an aggressive clinical course because of their rapid growth and high frequency of recurrence and distant metastasis [1,2].

We could find 8 cases of sarcomatoid carcinoma of the colon in the Medline search which the outcome of all patients reported indicate an aggressive biological course [1-6].

1) Kim JH, Moon WS, Kang MJ, et al. Sarcomatoid carcinoma of the colon: A case report. J Korean Med Sci 2001;16:657- 60.

2) Nakao A, Sakagami K, Uda M, et al. Carcinosarcoma of the colon: Report of a case and review of the literature. J Gastroenterol 1998;33:276-9.

3) Di Vizio D, et al. Sarcomatoid carcinoma of the colon: a case report with literature review. Tumori 2000;87:431-5.

4) Isimbaldi G, Sironi M, Assi A. Sarcomatoid carcinoma of the colon. Report of the second case with immunohistochemical study. Pathol Res Pract 1996;192:483-8.

5) Quban A, Nawanb RA, Coppola D. Diagnostic and pathogenetic implications of colorectal carcinomas with multidirectional differentiation: a report of cases. Clin Colorectal Cancer 2002;1:243-8.

6) Gentile R, Castellaneta A. Carcinosarcoma of the colon, one or two tumors? Pathologica 1997;89:62-8.