Primary de novo malignant giant cell tumor of kidney: a case report

BACKGROUND Osteoclast-like giant cell tumors are usually observed in osseous tissue or as tumors of tendon sheath, characterized by the presence of multinucleated giant cells and mononuclear stromal cells. It has been reported in various extraosseous sites including breast, skin, soft tissue, salivary glands, lung, pancreas, female genital tract, thyroid, larynx and heart. However, extraosseous occurrence of such giant cell tumors in the kidney is extremely rare and is usually found in combination with a conventional malignancy. De-novo primary malignant giant cell tumors of the kidney are unusual lesions and to our knowledge this is the second such case. CASE PRESENTATION We report a rare case of extraosseous primary denovo malignant giant cell tumor of the renal parenchyma in a 39-year-old Caucasian female to determine the histogenesis of this neoplasm with a detailed literature review. CONCLUSION Primary denovo malignant giant cell tumor of the kidney is extremely rare. The cellular origin of this tumor is favored to be a pluripotential mesenchymal stromal cell of the mononuclear/phagocytic cellular lineage. Awareness of this neoplasm is important in the pathological interpretation of unusual findings at either fine needle aspiration or frozen section of solid renal masses.