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Mucinous tubular and spindle cell carcinoma of the kidney

Mucinous tubular and spindle cell renal carcinoma (MTSC) shows proliferation of cells with eosinophilic cytoplasm, anastomosing tubules, mucinous extracellular matrix and low-grade nuclear cytology.

Keywords: mucinous renal cell carcinoma
Corresponding Author: Hannachi Sassi, Samia. Department of Pathology Salah Azaeiz Institute, Bab Saadoun 1006, Tunis, Tunisia. Phone : 00216 71 577 850, Email: samia.hannachi@rns.tn

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Samia HANNACHI SASSI, Raoudha DOGHRI, Karima MRAD, Imen ABBES, Maha DRISS, Naziha BEN HAMIDA, Dhekra KACEM, Khaled BEN ROMDHANE.
Department of Pathology Salah Azaeiz Institute, Bab Saadoun 1006, Tunis, Tunisia.
Case: A 76-year-old female presented with back pain for 1 month duration. Ultrasound abdomen revealed a right renal tumour. Urological CT scan showed a right tumour kidney arising in the medial back region without involvement of the perirenal fat and Gerota's fascia, regional lymph node, vascular involvement and liver lesion (Figure 1). The patient received a radical nephrectomy. Grossly, the specimen received consists of a right kidney with a 35x30x25mm tumour arising in the medial back region. The tumour was well limited of tan glistening colour. There were no cysts or hemorrhages. The calyces and pelvis, along with the ureter were not involved by the tumour (Figure 2). Histologically, the tumour consisted of cords and compressed tubules of cuboidal cells with low-grade nuclear features, and areas of spindle cell configuration. There were foamy macrophages arranged in small clusters (Figure 3), which were separated by a mucinous stroma (Figure 4) with intercellular alcian blue-positive mucinous material (Figure 5). Mitosis and vascular invasion were not found. There was neither sarcomatoid differentiation nor primarily papillary renal cell carcinoma component. Immunohistochemical study showed that the tumour cells were positive for pancytokeratin, cytokeratin 7 (Figure 6), epithelial membrane antigen, cytokeratin 19 (Figure 7) and vimentin (Figure 8). They were negative for cytokeratin 5/6, cytokeratins 20 and CD10. Morphologic appearance and immunohistochemical profile were consistent with a diagnosis of MTSC.
Discussion
The recent World Health Organization (WHO) classification of renal tumours officially included mucinous tubular and spindle cell carcinoma (MTSC) as a separate category (1). The WHO classification describes MTSC as low-grade tumour with a favourable prognosis, a wide age range (17–82 years, mean 53 years) and a female preponderance (male to female ratio of 1:4). Most tumours are single and asymptomatic, although flank pain and haematuria may occur. Macroscopically, they appear as large, well-circumscribed, homogenous, tan-white-pinkish lesions, sometimes centered in the renal medulla. These tumours have been well characterized and distinguished from other renal epithelial tumours by immunohistochemical and cytogenetic studies. These studies point out the morphologic relationships with the distal nephron and the loop of Henle or highlight the spindle cell component (1, 2, 3).
Histologically, these tumours consist of a mixture of tubules and cuboidal and spindle-shaped epithelia cells with low grade nuclei in a background mucinous extracellular matrix. The mucinous component is highlighted by alcian blue. The nuclei are bland, spherical or oval, with inconspicuous nucleoli. These low-grade nuclear features are the same in both the tubular and the spindle cell elements (1, 3).
The histological spectrum of MTSC, describes several MTSCs with unusual features and absence of the typical abundant extracellular matrix, which they termed a “mucin-poor” variant of MTSC (4). MTSC with focal neuroendocrine differentiation have also been reported (5). Simon et al (3) report a case of MTSC with extensive sarcomatoid differentiation, multiple metastases, and a rapidly fatal clinical course. Due to these histological variations, renal tumours with features of MTSC require careful histological examination and judicious use of immunohistochemical stains to exclude other histological types of renal cell carcinoma.
These tumours have a complex immunophenotype and stain for a wide variety of cytokeratins including low molecular weight keratins (CAM 5.2, MAK 6), CK7, CK 18, CK 19 and 34βE12. Epithelial membrane antigen is commonly present, and vimentin and CD15 staining may be seen. Markers of proximal nephron such as CD10 and villin are generally absent (1). Our case fulfils histological and immunohistochemical profile of conventional MTSC.
Cytogenetic data indicate various chromosomal losses and gains, but MTSC of the kidney has no characteristic pattern of genomic aberrations separating it from other subgroups of renal cell carcinomas (6, 7).
MTSC is low-grade tumour with a favourable prognosis, while in the literature, two metastatic cases were reported. Further investigations are required to determine the frequency and true prognosis of these tumours, which are easily identifiable morphologically (6).
Figure 1 CT scan showing right renal tumour
Figure 2 Gross morphology
Figure 3: Low-power view showing tubular areas admixed with solid spindly areas and clusters of foamy macrophages (haematoxylin and eosin, original magnification x100).
Figure 4: Bland spindle cell areas with interdissecting abundant mucinous material (haematoxylin and eosin, original magnification x400).
Figure 5: Alcian blue-positive mucinous material (original magnification x400).
Figure 6: Tumour cells are stained diffusely and strongly after immunostaining for cytokeratin 7 (left corner). Normally (right corner) in the non neoplastic kidney, cytokeratin 7 strongly stained the cytoplasm of the distal convoluted tubular cells. The proximal tubules and glomeruli were negative.
Figure 7: Tumour cells are stained diffusely and weakly after immunostaining for cytokeratin 19 (left corner). Normally (right corner) in the non neoplastic kidney, cytokeratin 19 strongly stained the cytoplasm of the distal convoluted tubular cells. The proximal tubules and glomeruli were negative.
Figure 8: Tumour cells are stained diffusely and strongly after immunostaining for vimentin.
REFERENCES
1. Eble JN, Sauter G, Epstein JI, Sesterhenn IA. World Health Organisation Classification. Pathology and Genetics. Tumours of the urinary system and male genital organs. Lyon : IARC Press, 2004.
2. Zhou M, Maggi-Galluzzi C. Genitourinary Pathology. Churchill Livingstone, 2007.
3. Simon RA, di Sant’Agnese PA, Palapattu GS, Singer EA, Candelario GD, Huang J, JL Yao. Mucinous Tubular and Spindle Cell Carcinoma of the Kidney with Sarcomatoid Differentiation. Int J Clin Exp Pathol 2008; 1: 180-184.
4. Fine SW, Argani P, DeMarzo AM, Delahunt B, Sebo TJ, Reuter VE and Epstein JI. Expanding the histological spectrum of mucinous tubular and spindle cell carcinoma of the kidney. Am J Surg Pathol 2006; 30:1554-1560.
5. Jung SJ, Yoon HK, Chung JI, Ayala AG and Ro JY. Mucinous tubular and spindle cell carcinoma of the kidney with neuroendocrine differentiation: report of two cases. Am J Clin Pathol 2006; 125: 99-104.
6. Ferlicot S, Allory Y, Compérat E, Mege-Lechevalier F, Dimet S, Sibony M, Couturier J, Vieillefond A. Mucinous tubular and spindle cell carcinoma: a report of 15 cases and a review of the literature. Virchows Arch 2005; 447: 978-983.
7. Brandal P, Lie AK, Bassarova A, Svindland A, Risberg B. Genomic aberrations in mucinous tubular and spindle cell renal cell carcinomas. Modern Pathology 2006; 19, 186-194


Date added to bjui.org: 24/10/2009 (publication information)
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