Fox Chase Cancer Center Researchers Document First Case of Rare Rectal Cancer and Its Genetic Signature

Shuanzeng “Sam” Wei, MD, PhD

Researchers at Fox Chase Cancer Center have documented the first case of rectal myxoid leiomyosarcoma (MLS), a rare cancer typically seen in the female reproductive system. The researchers also found a novel fusion gene that can be used to positively identify the cancer at the molecular level.

The findings should help clinicians and pathologists make more accurate diagnoses for better and more personalized treatment decisions, said first author Shuanzeng “Sam” Wei, MD, PhD, an Associate Professor in the Department of Pathology and Medical Director of the Clinical Genomics Laboratory at Fox Chase. He noted that MLS has several “mimics” that can make proper diagnosis especially difficult. 

“Different tumor types have different treatments or different prognoses, so getting the correct diagnosis is very important. I want to stress that it’s difficult to diagnose myxoid leiomyosarcoma, in part because the morphology is not typical to traditional leiomyosarcoma,” said Wei.

The tumor’s features are similar to other tumor types, such as myxoid liposarcoma, myxofibrosarcoma, extraskeletal myxoid chondrosarcoma, myxoid inflammatory myofibroblastic tumor, and endometrial stroma sarcoma with myxoid features, which can lead to misdiagnosis, he added. However, next-generation sequencing-based tests can assist in diagnosis.

Although rare, myxoid leiomyosarcoma is a well-documented cancer that often portends a poor prognosis compared to conventional leiomyosarcoma. It’s most often found in the uterus and external female genitalia, but has also been reported in the ovaries, prostate, stomach, esophagus, heart, and other locations. This is the first documented case of MLS in the rectum.

Wei said the case illustrates the importance of using advanced technology to diagnose tumors at the molecular level. “If you encounter a similar myxoid tumor, you should be careful and not just make a diagnosis lightly. Send it for molecular testing – for example what we are doing with next-generation sequencing – and look for the specific fusion gene to confirm the diagnosis.”

Researchers are continuing to follow up with the patient to collect data on their long-term outcome.

The case study, “Novel MIR143HG::PLAG1 Gene Fusion Identified in a Rectal Myxoid Leiomyosarcoma,” was published in Genes Chromosomes Cancer.