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
Received July 16, 2012; revised August 24, 2012; accepted September 7, 2012
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
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.  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 . 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.
opyright © 2012 SciRes. OJU
EL F. HINDE ET AL.
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.
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 . Their diameter var-
ied between 1.8 and 17 cm (mean diameter, 6 cm) .
The tumor is usually present as an asymptomatic mass,
often found on ultrasound. Occasionally, the patients
may present with flank pain or hematuria . 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 . 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 . Small numbers of cases with high
nuclear grade (Fuhrman grade 3) are reported . 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. 
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) . 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 . 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
Copyright © 2012 SciRes. OJU
EL F. HINDE ET AL. 221
of RCC since the Heidelberg classification of renal cell
tumors was published in 1997 . 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 . 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.
The authors thank Dr F. Mege-Lechevallier and Dr S.
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