Benign and low-grade cartilaginous tumors: an update on differential diagnosis

Cartilaginous neoplasms hold considerable share in the routine diagnostics of bone tumor pathology. Benign cartilage forming tumors, that are in general more frequent than their malignant counterparts, may often pose diagnostic challenges. Distinction of a benign cartilaginous lesion from a low-grade malignant tumor can render difficulties especially in a small biopsy material. Considering the divergent therapeutic and prognostic implications, a careful assessment of histologic, radiologic and clinical findings/features is very important, and an experienced multidisciplinary team is indispensable to achieve an accurate diagnosis. This mini review focuses on the histomorphological findings of benign, locally aggressive and low-grade cartilaginous tumors referring to the latest edition of WHO Classification of Tumors of Soft Tissue and Bone Tumors (fifth edition, 2020). The focus of this article is on the differential diagnosis of benign cartilaginous lesions and their distinction from other cartilaginous lesions, especially their malignant counterparts. Histomorphology, in correlation with imaging findings, serve as the cornerstone in the diagnosis of cartilaginous tumors. Based on overlapping morphological and radiological features between the tumor types, including benign and malignant ones, their diagnosis can be challenging. Emerging molecular findings play a notable role in understanding the underlying mechanisms involved in their development, though their routine use in molecular diagnostics is limited to few indications. Likewise, the role of immunohistochemistry remains limited in the differential diagnosis of the cartilaginous tumors, emphasizing the need for joined histological and radiological evaluation.