A newly identified type of tumor, characterized by a hard, bone-like exterior and surprisingly benign interior, has been officially classified, offering relief to patients who might otherwise undergo aggressive and unnecessary cancer treatment. The discovery, detailed in Modern Pathology, provides pathologists with critical tools to distinguish this unique growth from malignant sarcomas, which share some superficial similarities.
The Deceptive Appearance
The tumor initially presents as a hard mass, often found in limbs, resembling cancerous tissue. Patients frequently report discovering these growths—some as large as baseballs—painless but alarming. This resemblance to sarcoma, a rare but aggressive cancer accounting for roughly 1% of adult cancers, has historically led to misdiagnosis and inappropriate treatment. The key lies in the tumor’s unique genetic fingerprint, which does not align with known cancer indicators.
Years of Investigation
Pathologist John Gross first encountered this unusual case in 2022, noting its bony exterior and atypical cellular composition. The mass didn’t fit into established categories, containing keratin (a protein linked to certain cancers) but lacking the genetic markers typically associated with malignancy. Over three years, Dr. Gross tracked down 12 similar cases at other institutions, confirming a pattern of hard, painless growths in patients’ arms and legs.
Genetic Breakthrough
The turning point came through advanced molecular testing. By analyzing gene methylation patterns and performing comprehensive RNA sequencing, Dr. Gross’s team identified a recurring, previously unknown gene fusion present in the majority of cases. This unique “fingerprint” combined with other distinct characteristics provided definitive proof of a new category.
OSET: A New Classification
Researchers have named the tumor OSET (ossifying spindled and epithelioid tumor) based on its appearance and cellular structure. The classification allows for accurate diagnosis and treatment: surgical removal without the need for chemotherapy or radiation. No patients who underwent surgical removal have experienced tumor recurrence.
“One of the biggest problems is overtreatment and giving chemotherapy or radiation for something that really just is benign.” – John Gross, Johns Hopkins School of Medicine
The focus now is on raising awareness among clinicians, patients, and especially pathologists to ensure correct diagnoses. The discovery underscores the importance of precise genetic analysis in avoiding unnecessary and potentially harmful treatments for what is ultimately a benign condition.
