Misleading New Entity in Tumors of Kidney: A Case Report and Literature Review

doi:10.4236/oju.2012.24039

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Open Journal of Urology, 2012, 2, 219-222

http://dx.doi.org/10.4236/oju.2012.24039 Published Online November 2012 (http://www.SciRP.org/journal/oju)

Misleading New Entity in Tumors of Kidney: A Case

Report and Literature Review*

El Fatemi Hinde1#, Hammas Nawal1, Hafid Imane1, Tazi Fadl2, Elfassi Jamal2, Amarti Afaf1

1Department of Pathology, Hassan II Teaching Hospital, Fez, Morocco

2Department of Urology, Hassan II Teaching Hospital, Fez, Morocco

Email: #[email protected]

Received July 16, 2012; revised August 24, 2012; accepted September 7, 2012

ABSTRACT

Introduction: Mucinous tubular and spindle cell carcinomas (MTSCC’s) are recently described rare type of renal cell

carcinoma (RCC). They may have morphological similarities to papillary RCC (papRCC) and in our case to carcinoma

collecting ducts of Bellini. Case Report: We report a rare case of renal tumor, mucinous tubular and spindle cell carci-

noma in a 56-year-old woman. The tumor, located in the left kidney, was well circumscribed. MTSCC’s are characte-

rized by small, elongated tubules lined by cuboidal cells and/or cords of spindled cells separated by pale mucinous

stroma. Discussion: MTSCC is a rare type of renal cell carcinoma. Pathologists should be aware of the histological

spectrum of MTSCCs to ensure an accurate diagnosis. Careful attention to the presence of a spindle cell population may

be helpful in the differential diagnosis in tumors with predominant compact tubular growth.

Keywords: Renal Carcinoma; Mucinous Tubular and Spindle Cell Carcinoma; CD10; Immunohistochemistry

1. Introduction

Mucinous tubular and spindle cell carcinoma (MTSCC)

of the kidney is a novel neoplastic entity of renal cell

carcinoma (RCC) that has only recently been recognized.

It was first described in 1998 and specifically described

by Parwani et al. [1] a series of MTSCCs as a separate

entity. The recent World Health Organization classifica-

tion of renal tumors officially included MTSCC as a

separate category [2]. Because MTSCC has only recently

been recognized, there are no more than 80 cases re-

ported in the literature [1,3-5]. In the present report, we

report a case of MTSCC that showed unusual morphol-

ogic features of spindle cell predominance, psammoma-

tous calcification, and depletion of extracellular mucin.

2. Case Report

A 56-year-old woman had macroscopic hematuria for 1

month. She had no medical or family history of any ma-

lignancy. All of his laboratory data were within the nor-

mal ranges. Computed tomography revealed a huge renal

mass in the left kidney (Figure 1). No metastatic lesions

or lymph node enlargement were noted. The gross tumor

had dimensions of 12.5 × 12.0 × 10 cm and was located

in the inferior pole, confined to the renal parenchyma,

and surrounded by a pseudocapsule. The tumor was well

circumscribed and showed a variegated, grayish white

cut surface with hemorrhagic and necrotic areas. Renal

vein invasion and perinephric fat involvement were not

identified. The nephrectomy specimen was extensively

sampled. Sections were fixed in 10% neutral-buffered

formalin and processed for light microscopy via conven-

tional methods. Routine processing for histologic ex-

amination included paraffin embedding, sectioning, and

standard staining with hematoxylin and eosin safran.

Morphologically, the tumor showed predominantly spin-

dle cells arranged in fascicles composed of bland oval to

spindle nuclei with fine chromatin and small nucleoli

(Figure 2). There were tubular structures variably lined

by small cuboidal cells with eosinophilic cytoplasm and

focal psammoma bodies. Approximately 95% of the tu-

mor was composed of spindle cell carcinoma cells that

merged with areas of tubular structures. There was no

significant atypia, increased mitotic activity, or vascular

invasion identified. An interesting finding was focal

psammomatous calcification. There was depletion of

extracellular mucinous material throughout the sections

(Figure 2). The scant mucinous material was not appre-

ciated by hematoxylin and eosin stain but it required

mucin stain to be recognized. Some foamy histiocytes

and a inflammatory cells identified in the stroma with

necrotic and hemorrahgic areas. Three diagnoses were

suspected in these histological patterns: inflammatory

pseudo-tumours, carcinoma of collecting ducts of bellini

*The authors declare no conflict of interest.

#Corresponding author.

EL F. HINDE ET AL.

220

Figure 1. Computed tomography revealed a huge renal

mass in the left kidney.

Figure 2. Hematoxylin Eosin Safran (HES) × 40. Tumor

showed spindle cells arranged in fascicles composed of

bland oval to spindle nuclei with fine chromatin and small

nucleoli. Extracellular mucinous material.

and mucinous tubular and spindle cell carcinoma. Muci-

nous stroma was reactive for alcian blue and periodic

acid—Schiff stains. Immunohistochemical studies dem-

onstrated that tumor cells showed diffuse, intense stain-

ing for epithelial membrane antigen, cytokeratin (CK) 7,

8/18 and focally vimentin. The tumor cells were com-

pletely negative for CK20 and CD10.

3. Discussion

Although there is a relatively small number of series de-

tailing this Renal Cell Carcinoma, its unique morpho-

logical features and clinical presentation are sufficiently

characteristic that the World Health Organization has

recognized it as a distinct clinicopathologic entity. Much

is known about this tumor, but its histomorphological

features, histogenesis, and relationship to other renal cell

tumors remains undefined. MTSCC’s is preferentially

observed in adults. Patients’ age ranged from 21 to 81

years, with a mean and median of 55.8 and 58.5 years,

respectively. The male to female ratio was 1/3 [4,6]. The

right kidney was more involved [5]. Their diameter var-

ied between 1.8 and 17 cm (mean diameter, 6 cm) [4].

The tumor is usually present as an asymptomatic mass,

often found on ultrasound. Occasionally, the patients

may present with flank pain or hematuria [7]. The tumors

were generally confined (pT1 or pT2) in more than 80%

of the cases [4,5,8]. The radiological appearance of

mucinous tubular and spindle cell carcinoma is diverse

and therefore indistinguishable from the more common

subtypes of renal cell carcinoma [9]. Grossly, tumors are

mainly circumscribed and can be large and are usually

contained within the renal capsule. Histologically, tu-

mors show tubules or cords of cuboidal cells that transi-

tion to sheets of spindle cells against a basophilic muci-

nous matrix. The epithelial nuclei are round to ovoid and

bland, and mitotic figures are rare. Either spindle or tu-

bular components can predominate, and mucin can be

sparse or absent. Foamy macrophages, heterotopic bone,

and psammomatous calcification are described as well as,

rarely, necrosis [6]. Small numbers of cases with high

nuclear grade (Fuhrman grade 3) are reported [10]. True

sarcomatoid change has also rarely been described

[11,12], with authors noting, in addition to classic

MTSCC morphology, high-grade spindled areas resembling

fibrosarcoma and undifferentiated pleomorphic sarcoma,

with necrosis and a high proliferation index. MTSCC

tumors have a complex immunoprofile. Shen et al. [8]

demonstrated the expression of differentiation markers of

proximal tubules, which were renal cell carcinoma marker

antigen (RCC Ma) (92%), a-Methylacyl-COA racemase

(AMACR) (92%), CD15 (Leu M1) (67%) as well as

CK7, which is known to stain the distal tubules (92%).

Positive staining was seen with markers that were found

in the collecting duct epithelium, including EMA and

peanut agglutinin (PNA) [4]. The remaining markers,

which are more specific to the proximal tubules, are

CD10, the collecting duct (aquaporin 3) and the kidney-

specific cadherin expressed in only a few cases [8,13].

The vimentine positivity was infrequent. It is observed in

14% - 40% of the cases [4,8,13]. The proliferative rate

(MIB-1) was low, suggesting a low proliferation activity,

[4,14] a finding that may in part explain the low malig-

nancy of this tumor type. Mucinous tubular and spindle

cell carcinoma with spindle cell predominance may

simulate a variety of benign or malignant spindle cell

renal tumors. In cases with limited diagnostic material,

such as fine-needle biopsy specimens, it is important to

recognize that this spindle cell morphology may occur in

MTSCC and may necessitate differential diagnostic con-

sideration from other spindle cell neoplasms [15]. The

major differential diagnosis of the mucin-poor spindle

cell predominance MTSCC is the sarcomatoid differen-

tiation (SD) that has been recognized to arise in all types

EL F. HINDE ET AL. 221

of RCC since the Heidelberg classification of renal cell

tumors was published in 1997 [16]. The presence of SD

in RCC represents high-grade transformation that has a

deleterious effect on prognosis. Tumors containing SD

have a decreased 5-year survival rate from 79% to 22%

in stage-matched patient cohorts; tumors containing more

than 50% SD have an even worse prognosis [17]. Muci-

nous tubular and spindle cell carcinoma lacks large, hy-

perchromatic/pleomorphic nuclei or significant mitotic

activity and had a much more uniform architectural pat-

tern. Ki-67 can be helpful in demonstrating the low pro-

liferation rate in MTSCC. The widening spectrum of

MTSCC in recent years has led to the description of

atypical, sarcomatoid and metastatic cases as well [10,

14]. It therefore seems more important to be aware of

such morphological changes in MTSCC diagnosis and

employ IHC analysis [18,19] However, there are also

cases that are extremely similar to papRCC in the diffe-

rential diagnosis [5,8]. Fluorescent in situ hybridization

or comparative genomic hybridization studies may take

the place of IHC investigation in the differential diagno-

sis. These studies have reported multiple chromosomal

losses including 1, 4, 6, 8, 11, 13, 14, 18, 22 instead of

chromosomal additions [4,13,20,21]. The chromosome 3

losses that are typical for clear RCC have not been found.

In summary, we report a case of mucin poor spindle

cell predominance MTSCC with psammomatous calcifi-

cation that expands the histologic spectrum encountered

in these tumors that may overlap with other renal neo-

plasms and can be a diagnostic dilemma. Awareness of

variable morphologic variants of MTSCC is important to

avoid a misdiagnosis.

4. Acknowledgements

The authors thank Dr F. Mege-Lechevallier and Dr S.

Collardeau Franchon for their help in the diagnosis.

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