Case 6 -

Mucinous Tubular and Spindle Cell Carcinoma John N Eble, M.D. Holger Moch, M.D.

Case history: 53 year old woman. Detection of a renal mass by CT. A nephrectomy was performed. The patient is free of disease 5 years after nephrectomy. Macroscopic findings: The tumor showed well-circumscribed solid tumor with a uniform gray cut surface. Diagnosis: Mucinous tubular and spindle cell carcinoma Mucinous tubular and spindle cell carcinomas are low grade polymorphic renal epithelial neoplasms with mucinous tubular and spindle cell features. The new WHO classification has included this new tumor subtype. The tumors usually present as asymptomatic masses, often found on ultrasound. There is a wide age range from 17 to 82 years and a male to female ratio of 1:4. Macroscopically, mucinous tubular and spindle cell carcinomas are well circumscribed and have grey or light tan cut surfaces. The tumors are composed of tightly packed, elongated tubules separated by mucinous stroma. Sometimes, the tumors simulate leiomyoma or sarcoma. Many of these tumors had been previously diagnosed as unclassified, sarcomatoid carcinomas or as duct Bellini carcinomas. The tumors have a complex immunophenotype and stain for cytokeratin and EMA. Markers of proximal nephron such as CD10 are absent. By using comparative genomic hybridization and fluorescence in situ hybridization, there is a characteristic combination of chromosome losses, generally involving chromosome 1, 4, 6, 8, 13 and 14. The prognosis seems to be favorable. It has been postulated that these tumors are related to the loop of Henle. However, the immunohistochemical and cytogenetic analysis showed complex immunophenotypes, but could not prove a derivation from the loop of Henle. There was no genetic relationship to clear cell renal carcinomas. References Eble JN, et al. Tumours of the Kidney, in Tumours of the Urinary System and Male Genital Organs. IARC Press: Lyon, 2004. Rakozy C, et al. Low-grade tubular-mucinous renal neoplasms: morphologic, immunohistochemical, and genetic features. Mod Pathol 15: 1162-71, 2002. Weber A, Srigley J and Moch H. [Mucinous tubular and spindle cell carcinoma of the kidney. A molecular analysis]. Pathologe 24: 453-9, 2003. MacLennan GT, Farrow GM, and Bostwick DG. Low-grade collecting duct carcinoma of the kidney: report of 13 cases of low-grade mucinous tubulocystic renal carcinoma of possible collecting duct origin. Urology 50: 679-84, 1997 Parwani AV, et al. Low-grade myxoid renal epithelial neoplasms with distal nephron differentiation. Hum Pathol 32: 506-12, 2001.