Benign clear cell tumor (‘sugar’ tumor)
It is a rare tumor, occurring in any age as an asymptomatic peripheral nodule. Because of their immunohistochemical and ultrastructural features, they have been supposed to origin from pericytes; anyway, their origin is a matter of discussion. They consist of polygonal cells with clear, glycogen-rich cytoplasm.
Cytologic diagnostic features
- Clusters of polygonal and spindle-shaped cells
- Vacuolated or granular cytoplasm
- PAS-positive cytoplasm
- Non-small cell carcinoma with clear cell change
- Carcinoid tumor
- Metastatic renal cell carcinoma
Immunocytochemistry is helpful: most sugar tumors are positive for HMB-45, CD34 and S-100 and negative for cytokeratins and CEA.
It presents as an incidental nodule on radiographs, particularly in elderly men. A hamartoma is a neoplasm in an organ that is composed of tissue elements normally found at that site, but growing in a haphazard mass.
Transthoracic FNA is very sensitive and specific in diagnosing this lesion. A mixture of mesenchymal (mainly fibromyxoid and cartilaginous material) and epithelial elements is seen in FNA material. Bland spindle cells in a fibromyxoid stroma and mature cartilage, with chondrocyte in lacunae, are observed; epithelial glandular cells and adipocytes are often present.