Soft tissue sarcomas are rare mesenchymal tumors, with an incidence of fewer than six cases per 100,000 inhabitants. They account for only 1-2% of cancers in adults.1 Some have coexisting epithelial and mesenchymal components, and so are classified as sarcomatoid carcinomas.2 Their habitual locations are the head, neck, and female reproductive tract; they can also be present in the esophagus and stomach, but their location in the colon is exceptional.3 Metaplastic theory is the most widely accepted histogenesis hypothesis for these tumors, positing that the sarcomatoid component originates in metaplasia of the epithelium, which would explain cytokeratin marker positivity in the mesenchymal component.4 The recent use of molecular tools has enabled a more precise classification of this tumor to be made, while identifying common alterations, such as gene translocations, kinase pathway disruptions, epigenetic deregulation, genomic instability, and failures in the mechanisms of replication and cell survival, which has facilitated the development of targeted therapies.5

An 84-year-old man with a past medical history of controlled high blood pressure, had symptom onset three months earlier, primarily with constipation, loss of appetite, weight loss (approximately 12 kg), early satiety, bloating, asthenia, and adynamia. Symptomatic treatment for irritable bowel syndrome was given, with no improvement, so he sought further medical attention. At hospital admission, the patient presented with a 2 cm enlargement of the liver under the costal margin, as well as a poorly defined, mobile abdominal mass located in the right colonic frame that was not painful upon palpation. Given those findings, complementary studies were ordered. A liver and biliary tract ultrasound reported hepatomegaly with a heterogeneous granular parenchyma and the presence of nodules and isoechoic and hypoechoic nodules with metastatic characteristics, with bright points suggestive of microcalcifications, as well as a multi-lobulated anechoic mass that compressed and displaced the gallbladder. A contrasted computed tomography scan of the chest, abdomen, and pelvis confirmed the findings in the liver and revealed concentric and asymmetric thickening of the colonic wall, measuring between 15 and 21 cm, with punctate calcifications and a total length of approximately 71 mm at the level of the hepatic angle. A rounded lymph node, measuring 6 mm in diameter, was identified, along with multiple diverticula in the sigmoid colon and descending colon, and no signs of metastatic involvement in other organs (Fig. 1). Colonoscopy with biopsy was then carried out that revealed an indurated neoproliferative lesion occluding the entire intestinal lumen and covered by fibrinopurulent exudate at the junction of the mid and lower third of the ascending colon. Lesion histopathology reported well-differentiated and ulcerated intestinal adenocarcinoma. Due to the persistence of the intestinal obstruction, laparotomy with right hemicolectomy plus transverse ileum resection with end-to-side anastomosis was performed. The histopathologic report of the surgical specimen stated negative surgical margins, with two of the seven lymph nodes identified as metastatic, thus establishing the final diagnosis of high-grade sarcomatoid carcinoma (G4) composed of mucinous (60%), intestinal (20%), micropapillary (5%), and sarcomatoid (15%) elements. The tumor infiltrated the submucosa, muscularis propria, and pericolonic tissues, without perforating the visceral peritoneum, but with lymphovascular invasion (Fig. 2A-D). After his satisfactory postoperative progress, the patient was referred to the medical oncology outpatient service to evaluate adjuvant treatment, given the irresectability of liver metastases.

Figure 1.

Coronal view of a computed tomography scan of the chest, abdomen, and pelvis, with IV contrast, showing thickening of the wall of the ascending colon and a heterogeneous liver parenchyma due to metastatic activity.

Figure 2.

Histologic section (H&E x4). A and B) Intestinal tumor with a mucinous component and the presence of bone tissue is seen. Intensely eosinophilic areas are identified in the central area (pink) with trabecular structure and the presence of osteocytes in lacunae. A mucinous component is also seen in the lighter-colored zones with loose, slightly basophilic, extracellular matrix, surrounding the areas peripheral to the bone tissue. C and D) Eosinophilic islets of fragments of the bone matrix are seen surrounded by loose mesenchymatous tissue and atypical cells characterized by irregular-shaped nuclei, hyperchromasia, and nuclear pleomorphism (black outline).

In the present case, a mesenchymal tumor in the colonic region of an advanced-age adult patient was confirmed. The sarcomatoid component suggests the term “carcinosarcoma” but that entity is not recognized by the World Health Organization (WHO) in digestive tract tumors, and so the correct terminology is carcinoma with a sarcomatoid component.6 Until now, only 33 cases of this tumor have been reported in the colon, primarily in the rectum, and only six in the ascending colon,7 highlighting the importance of the present case. The first documented case was in 1985, with a fatal outcome four years after diagnosis.8 There are currently no standardized treatment guidelines. However, patients treated at specialized, high-volume centers present with better results. Management tends to start with surgical resection with negative margins, followed in some cases by chemotherapy or radiotherapy,9 as occurred with our patient. Even so, these sarcomas are challenging, due to their low diagnostic sensitivity, limited therapeutic options, and the difficulty for developing clinical trials.10 Their rareness has impeded the establishment of specific clinical guidelines. Nevertheless, surgical resection continues to be the therapeutic cornerstone, occasionally complemented with chemotherapy or radiotherapy. A relevant limitation of the present case was the impossibility to perform immunohistochemical tests (desmin and CD 117) because of a lack of supplies at the host institution, and so the diagnosis was based solely on characteristic histologic findings considered sufficient in the well-defined clinicopathologic contexts. In conclusion, the evidence suggests that treatment at specialized centers improves outcomes, underlining the need to centralize care and promote studies that standardize the approach to these rare cases, as well as the importance of a detailed diagnostic process, to abolish diagnostic uncertainty.