In a paper appearing in Modern Pathology, John Gross, M.D., associate professor of pathology and orthopedic surgery at the Johns Hopkins University School of Medicine, describes in detail for the first time a slow-growing, bone-covered, noncancerous mass that he named the ossifying spindled and epithelioid tumor, or OSET. The danger for patients with an OSET, he explains, is not from the tumor itself, but that it could be mistaken for a malignant growth and lead to a patient receiving unnecessary chemotherapy or radiation treatments.

Discovery and initial identification of OSET

“The index case biopsy sample that led to the OSET discovery was from a patient with a bone-covered tumor that a colleague sent to me in consultation,” Gross says. “Under the microscope, it had traits that mimicked those of cancerous tissue, such as being hypercellular [composed of many tumor cells] and being positive for cytokeratins [proteins commonly seen in epithelial, or surface-lining, cells]; however, there were other features, such as the indolent bony shell that made me believe it was not likely a malignancy.”