Phosphaturic mesenchymal tumors. A polymorphous group causing osteomalacia or rickets

Area of Science:

• Pathology
• Oncology
• Endocrinology

Background:

• Mesenchymal tumors can manifest with paraneoplastic syndromes, including oncogenic osteomalacia or rickets.
• Understanding the diverse histopathological features of these tumors is crucial for accurate diagnosis and management.
• Previous classifications have not fully captured the spectrum of mesenchymal tumors associated with these metabolic bone diseases.

Purpose of the Study:

• To describe the clinicopathologic features of 17 mesenchymal tumors causing osteomalacia or rickets.
• To classify these tumors into distinct morphological groups.
• To correlate tumor morphology with clinical behavior and location.

Main Methods:

• Retrospective analysis of 17 surgically resected mesenchymal tumors.
• Detailed histopathological examination, including assessment of cellular morphology, matrix production, and vascularity.
• Classification into four morphological groups based on predominant tissue components and resemblance to known bone or soft tissue tumors.
• Review of clinical data, including tumor location, recurrence, and metastasis.

Main Results:

• Seventeen mesenchymal tumors causing osteomalacia/rickets were analyzed.
• Ten tumors exhibited mixed connective tissue features with vascular and/or osteoclast-like giant cells, often in soft tissue with benign behavior.
• Six tumors occurred in bone and were classified as osteoblastoma-like (4), nonossifying fibroma-like (2), and ossifying fibroma-like (1), all with benign behavior.
• One soft tissue tumor recurred locally and metastasized, representing the only malignant case.

Conclusions:

• Mesenchymal tumors causing osteomalacia/rickets are histologically diverse and can be classified into four main morphological groups.
• The majority of these tumors, particularly those with mixed connective tissue features, occur in soft tissue and behave benignly.
• Tumors resembling known bone tumors also present with benign behavior, highlighting the importance of comprehensive histopathological evaluation for accurate diagnosis and prognosis.