Figure 1:

Fumarate hydratase (FH)-deficient renal cell carcinoma, multifocal (FH case #1, 25 year old male). The nephrectomy specimen contained multiple oncocytic tumor nodules. The main neoplasm and all of the others demonstrated a solid tubular architecture (A). Occasional psammoma bodies were noted (B). On high power examination, nuclei were round with punctate but non-prominent nucleoli (C). The largest tumor nodule was separated from the surrounding kidney by a thin fibrous capsule (D). These neoplasms demonstrated loss of fumarate hydratase labeling (E, topportion of the figure) and aberrant expression of 2SC (F, topof the figure). The multiple tumor nodules included an incipient unencapsulated oncocytic nodule (G) which similarly demonstrated loss of fumarate hydratase immunoreactivity (H) and aberrant expression of 2SC (I). Interestingly, single 2SC immunoreactive cells were found at the edge of this incipient nodule and elsewhere in the uninvolved kidney.