The collecting duct carcinoma of the kidney: a cytogenetical study.

OBJECTIVES: The Heidelberg classification of renal tumours identifies five histotypes of renal cancer, underlining for two of them (conventional and papillary renal cancers) a strict relation between the morphological aspect and the complement of alterations evidenced by the cytogenetic analysis of the neoplastic karyotype. Due to its low incidence, the collecting duct carcinoma (CDC) has not yet been characterized from a cytogenetic point of view. This study analyses the clinical, morphologic and cytogenetic features of the CDC observed and treated in our department.

METHODS: From January 1995 to December 2002, among the 591 patients who underwent surgery for renal cancer, we observed 11 cases of CDC (prevalence 1.9%) treated either by radical (9 cases) or partial nephrectomy (2 cases). During radical nephrectomy a loco-regional lymphadenectomy was always performed. In the 9 cases observed after 1997, a complete cytogenetic analysis of the neoplastic karyotype was carried out.

RESULTS: At pathological examination the disease was found to be confined to the renal capsule (TNM 1997 stage 1) in only 3 patients; venous neoplastic trombosis and nodal metastasis were present in 3 and 6 cases respectively; 2 patients showed distant metastases (lung, bone). Two of the patients affected with stage 1 tumours are still alive with no evidence of the disease at 48 and 88 months after surgery, while the third died following the systemic progression of a concomitant bladder carcinoma. One patient with stage 4 tumour (no. 11) is alive, but the follow up time is still limited (2 months). All the other 7 patients are dead after a mean survival time of 16.3 months (range 0-45). As for cytogenetic analysis, 2 CDCs didn't grow in culture and in one case no karyotype alterations were reported. In the remaining 6 cases hypodiploid stemlines and a homogeneous chromosome alteration pattern were observed, with multiple numerical and structural aberrations (mean 11.1, range 7-15) and the continuous involvement of chromosomes 1 and X or Y, both as traslocation and deletion/monosomy. Additional abnormalities of chromosomes 22 and 13 were found to be common but less frequent.

CONCLUSIONS: The clinical behaviour of the CDC is aggressive and its prognosis is surely poor; surgical treatment seems to be curative only for organ-confined cancer, accounting for the minority of cases. This neoplasm is cytogenetically characterized by hypodiploid stemlines with common involvement of chromosome 1 and the autosomes.