Rare Sigmoid Colon Malignancies Present Diagnostic Challenges in Case Reports

The sigmoid colon typically follows a predictable anatomical path, but when rare tumors or structural anomalies emerge, the diagnostic process becomes a high-stakes exercise in precision. Two distinct clinical cases illustrate this volatility: one involving an aggressive, rare sarcoma and another involving a tumor located in a colon that had migrated to the wrong side of the abdomen.

Leiomyosarcoma: A Rare and Aggressive Sigmoid Malignancy

Leiomyosarcomas of the sigmoid colon are extremely rare tumors, representing less than 0.1% of all colorectal malignancies. Because their clinical and radiological features are often non-specific, a definitive diagnosis is only established after an anatomopathological examination.

In a 2021 case report published in Radiology Case Reports by Narjisse Aichouni et al., from the Department of Radiology and Department of Pathology at Mohammed VI University Hospital, Faculty of Medicine, University Mohammed First, a 70-year-old male smoker with arterial hypertension presented with abdominal pain and a hypogastric mass. A computed tomography has shown a voluminous heterogeneously enhancing tumor process with a necrotic center, attached to the sigmoid wall, with multiple secondary peritoneal and hepatic masses.

The pathology of this specific tumor was characterized by tumoral proliferation composed of fascicles of spindle cells, exhibiting smooth muscle differentiation and cigar-shaped nuclei showing moderate to severe atypia, and an abundant eosinophilic cytoplasmic. The report noted that numerous mitotic figures can be identified and identified areas of tumoral necrosis. To confirm the leiomyosarcoma diagnosis, researchers used immunohistochemistry, finding the cells positive for SMA, Desmine, and H-caldesmone, while they were negatif for CD117 and DOG1.

Anatomical Anomalies: Carcinoma in a Right-Sided Sigmoid Colon

While the previous case dealt with a rare cell type, a 2022 report published in World J Clin Cases by Liang-Jing Lyu et al., from the Department of Radiology at Tongren Hospital, Shanghai Jiao Tong University School of Medicine, focused on a rare anatomical variation. A 56-year-old Chinese man was admitted to the hospital with abdominal pain, but preoperative CT revealed a redundant sigmoid colon with a mass on the right side of the cecum and ascending colon—an anomaly that the authors state should be considered as a possibility by surgeons and radiologists before surgery.

The imaging showed a redundant sigmoid colon with a mass located on the right side of the cecum and ascending colon. Further analysis revealed that the descending colon crossed to the right at the level of the L4 vertebra and continuing as the sigmoid colon on the right, and the inferior mesenteric artery is shown running to the right instead of its normal left-sided course. This displacement indicated that the cecum was undescended during embryogenesis, as the cecum was displaced toward the left at the level of the L4 transverse process instead of the right pelvic region.

Laparoscopy confirmed an abnormal course in the descending colon and sigmoid colon. Subsequently, hemicolectomy was performed in an open manner after laparoscopic exploration. Pathological examination revealed an infiltrative mucinous adenocarcinoma with two lymph node metastases. The patient was discharged without any complications after a week, and there were no signs of recurrence or metastasis during the 3-month follow-up period.

Comparative Diagnostic Challenges in Colorectal Cases

Both cases underscore the necessity of advanced imaging and pathology to prevent misdiagnosis, though the risks differ based on the pathology. In the case of the right-sided sigmoid colon, the authors concluded that this rare anomaly should be differentiated from ascending colon cancer and pericecal hernia to prevent errors and other surgical complications.

For the leiomyosarcoma patient, the challenge was the aggressive nature of the tumor and its non-specific radiological appearance. For the carcinoma patient, the challenge was the extremely rare anatomic variation of the colon itself, which displaced the cecum toward the left at the L4 transverse process.

Readers should consult with qualified healthcare professionals for clinical guidance and medical advice regarding colorectal malignancies and anatomical variations.