Figure 2

Sixteen years after resection of the SDH-deficient RCC, patient 5 developed widespread metastases involving lungs, liver, rib, and vertebrae. A lung metastasis was sampled by fine-needle aspiration. Diff-Quik-stained direct smears (a) revealed clusters of monotonous epithelioid cells with granular cytoplasm. A cell block preparation was composed of a similar population of cells with eosinophilic cytoplasm and occasional cytoplasmic vacuoles (b), identical to that of the primary tumor. By immunohistochemistry, the neoplastic cells were positive for PAX8 (c) and negative for SDHB (d), supporting the interpretation of metastatic SDH-deficient RCC. Rare inflammatory cells show weak staining for SDHB (d).