FINAL DIAGNOSIS: - MODERATELY DIFFERENTIATED RENAL CELL CARCINOMA, CLEAR CELL VARIETY OF THE RIGHT KIDNEY WITH MULTIFOCAL ANGIOMYOLIPOMA WITHIN THE KIDNEY AND PERINEPHRIC LYMPH NODES.
Tuberous sclerosis (TS) is an autosomal dominant inheritable disorder with variable penetrance which affects many organ systems including the brain, heart, kidneys, and skin. The majority of the manifestations of this disease is a result hamartomatous growths, like the angiomyolipomas in this case, which lead to dysfunction such as seizures, cardiac arrhythmias, or renal failure in the affected organ. Patients with TS may also develop true neoplasms such as giant cell astrocytoma and, as in this case, renal cell carcinoma.
In the recent past our understanding of the genetic error responsible for TS has greatly increased with the identification of the TSC1 and TSC2 chromosomal loci. TSC1, located on chromosome 9, and TSC2, located on chromosome 16, are mutated in approximately 50 % of familial TS. In addition, in the Eker rat, an autosomal dominant hereditary renal carcinoma animal model, a germline mutation in the murine homolog of TSC2 has been identified, lending support to the hypothesis that this locus is a mediator of renal neoplasms.
The presence of renal cell carcinoma and angiomyolipoma in a single kidney is a rare event with only 34 cases being reported in the English literature. The majority of these cases (twenty) have been reported in patients with TS. Bjornsson et al reported that renal cell carcinomas arising in the background of TS have microscopic characteristics which distinguish them from sporadic renal cell carcinomas with there being a higher frequency of sarcomatoid differentiation with the neoplastic cells being immunoreactive with HMB-45 and frequently non-immunoreactive for cytokeratins. None of these features were present in this case.
The presence of angiomyolipomas within both the kidney and perinephric lymph nodes is not an ominous sign. Follow up studies in patients with both renal and lymph node involvement by an angiomyolipoma have shown that all reported patients are alive, with a follow up time ranging from 3 to 18 years. Therefore, it is felt that the presence of angiomyolipoma deposits within lymph nodes is consistent with a benign angiomyolipoma.