Abstract Background The skeletal muscle is an unusual site for metastasis from renal cell carcinoma (RCC). Metastatic RCC must be differentiated from benign primary soft-tissue tumors because aggressive surgical resection is necessary. Case presentation We present the case of a 65-year-old man with metastatic RCC in the gluteus maximus muscle (3.8 cm in diameter) found on enhanced computed tomography (CT) 6 years after nephrectomy. Retrospectively, the small mass (1 cm in diameter) was overlooked 5 years earlier on enhanced CT. Because the growth of the lesion was slow, benign tumor was a differential diagnosis. However, magnetic resonance imaging (MRI) showed that the mass had high-signal intensity on T1- and T2-weighted images (WIs) compared to that of skeletal muscle, with mild enhancement by Gadolinium. The MRI features were unusual for most soft-tissue tumors having low-signal intensity on T1-WI and high-signal intensity on T2-WI. Therefore, under a diagnosis of metastatic RCC, the lesion was resected together with the surrounding skeletal muscle. The histology was confirmed to be metastatic RCC. Conclusion MRI features of metastatic RCC may be beneficial in differentiating it from primary soft-tissue tumor.</p

Akio Sakamoto

Akira Yokomizo

C S.

Chen CK

Coppa GF

De Beuckeleer LH

Di Tonno F

Holland JM

Iwamoto Y

Kazuhiro Tanaka

Linn JF

McNichols DW

Nabeyama R

Ruiz JL

Schatteman P

Shuichi Matsuda

Suguru Matsuura

Tatsuya Yoshida

Teo EL

Thrasher JB

Yoshifumi Hori

Yoshinao Oda

Yukihide Iwamoto

English

PubMed

Springer - Publisher Connector

BioMed Central
World Journal of Surgical Oncology
ssOpen AcceCase report
Metastasis to the gluteus maximus muscle from renal cell 
carcinoma with special emphasis on MRI features
Akio Sakamoto*1, Tatsuya Yoshida1, Suguru Matsuura2, Kazuhiro Tanaka1, 
Shuichi Matsuda1, Yoshinao Oda2, Yoshifumi Hori3, Akira Yokomizo3 and 
Yukihide Iwamoto1
Address: 1Department of Orthopedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan, 2Department 
of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan and 3Department of Urology, 
Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan
Email: Akio Sakamoto* - akio@med.kyushu-u.ac.jp; Tatsuya Yoshida - yoshidat@ortho.med.kyushu-u.ac.jp; 
Suguru Matsuura - matsus@surgpath.med.kyushu-u.ac.jp; Kazuhiro Tanaka - tanaka@ortho.med.kyushu-u.ac.jp; 
Shuichi Matsuda - mazda@ortho.med.kyushu-u.ac.jp; Yoshinao Oda - oda@surgpath.med.kyushu-u.ac.jp; 
Yoshifumi Hori - dagutrio@surgpath.med.kyushu-u.ac.jp; Akira Yokomizo - yokoa@uro.med.kyushu-u.ac.jp; 
Yukihide Iwamoto - yiwamoto@ortho.med.kyushu-u.ac.jp
* Corresponding author    
Abstract
Background: The skeletal muscle is an unusual site for metastasis from renal cell carcinoma
(RCC). Metastatic RCC must be differentiated from benign primary soft-tissue tumors because
aggressive surgical resection is necessary.
Case presentation: We present the case of a 65-year-old man with metastatic RCC in the
gluteus maximus muscle (3.8 cm in diameter) found on enhanced computed tomography (CT) 6
years after nephrectomy. Retrospectively, the small mass (1 cm in diameter) was overlooked 5
years earlier on enhanced CT. Because the growth of the lesion was slow, benign tumor was a
differential diagnosis. However, magnetic resonance imaging (MRI) showed that the mass had high-
signal intensity on T1- and T2-weighted images (WIs) compared to that of skeletal muscle, with
mild enhancement by Gadolinium. The MRI features were unusual for most soft-tissue tumors
having low-signal intensity on T1-WI and high-signal intensity on T2-WI. Therefore, under a
diagnosis of metastatic RCC, the lesion was resected together with the surrounding skeletal
muscle. The histology was confirmed to be metastatic RCC.
Conclusion: MRI features of metastatic RCC may be beneficial in differentiating it from primary
soft-tissue tumor.
Background
Renal cell carcinoma (RCC) has widespread and unpre-
dictable metastatic potential [1], even after curative
nephrectomy is performed [2,3], RCC is able to metasta-
size to virtually any site. The most common sites of meta-
static RCC are the lungs, lymph nodes, bones, liver and
brain [4]. In several autopsy series, about 0.4% of cases
with RCC had skeletal muscle metastases [2].
Making a diagnosis of metastatic RCC to the skeletal mus-
cle is challenging, because the site is unpredictable, in
addition to it being rare. Furthermore, cases of metastasis
Published: 4 August 2007
World Journal of Surgical Oncology 2007, 5:88 doi:10.1186/1477-7819-5-88
Received: 5 May 2007
Accepted: 4 August 2007
This article is available from: http://www.wjso.com/content/5/1/88
© 2007 Sakamoto et al; licensee BioMed Central Ltd. 
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), 
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Page 1 of 4
(page number not for citation purposes)
World Journal of Surgical Oncology 2007, 5:88 http://www.wjso.com/content/5/1/88arising long after nephrectomy have been reported [2,5].
The differential diagnosis is primary soft-tissue tumor. It is
particularly important that benign soft-tissue tumor
should be differentiated, because aggressive surgical resec-
tion is necessary for metastasized RCC, but not for benign
soft-tissue tumor [6].
Generally, either open or needle biopsy is necessary in
order to make a diagnosis, in cases of soft-tissue tumor,
because the surgical procedure is different depending
upon the histological diagnosis. In the current paper, we
present a case of RCC with metastasis to the gluteus mus-
cle. The lesion was treated without biopsy, because the
MRI features suggested metastatic RCC. We wish to
emphasize the MRI features of metastatic RCC to the skel-
etal muscle, which could be beneficial in differentiating
metastatic RCC from primary soft-tissue tumor.
Case presentation
A 59-year-old man underwent right radical nephrectomy
for RCC of 3.8 centimeters in diameter (stage pT1a N0
M0). One year after the nephrectomy (when he was 60
years old), recurrence was seen in the adrenal gland. Con-
sequently, resection of the adrenal gland was undertaken.
Six years after the nephrectomy (when he was 65 years
old), a routine checkup using computed tomography
(CT) of the chest and abdomen detected a small mass in
the gluteus maximus muscle. The tumor was located in
the gluteus maximus muscle adjacent to the fascia, and
this was enhanced by contrast medium (Figure 1). On
physical examination, the tumor was palpable in the glu-
teus maximus muscle. He had no tenderness or referred
pain. Retrospectively, the tumor had been visible 5 years
earlier, 1 year after the nephrectomy, as a mass of 1 cm in
diameter (Figure 1). CT examination had not included the
area of the gluteus maximus muscle until the latest CT
examination.
Magnetic resonance image (MRI) showed that the lesion
adjacent to the fascia had higher signal intensity than that
of skeletal muscle on T1- and T2-weighted, and T2-STIR
images. The lesion had a rather regular border to the sur-
rounding gluteus maximus muscle, and was capsulated by
a thin area with low-signal intensity on both T1- and T2-
weighted images (Figure 2A–2H). Edema of low-signal
intensity on T1-weighted and high-signal intensity on T2-
weighted images was observed (Figure 2A–2B). The lesion
was mildly homogeneously enhanced by Gadolinium on
T1-weighted imaging (Figure 2C).
Primary soft-tissue tumor was a differential diagnosis.
Because the growth of the lesion was slow over 5 years,
benign soft-tissue tumor was suspected. The fact that the
lesion was capsulated by a thin area as seen on MRI also
supported the diagnosis. However, the MRI features were
unusual for most soft-tissue tumors having low-signal
intensity on T1-weighted imaging and high-signal inten-
sity on T2-weighted imaging. Therefore a diagnosis of
metastatic RCC was suspected rather than primary soft-tis-
sue tumor. Because metastatic RCC was strongly sus-
pected, wide resection including the surrounding skeletal
MRI shows diffuse high-signal intensity on T1- (A, D, F; TR/TE = 487/9.5) and T2- (B, E, G; TR/TE = 3500/89) weighted images with cap ulation of low-signal intensity on T1- and 2-weighte  images (A, B; axial, D, E; sagittal, F, G; coronal)Figure 2
MRI shows diffuse high-signal intensity on T1- (A, D, F; TR/
TE = 487/9.5) and T2- (B, E, G; TR/TE = 3500/89) weighted 
images with capsulation of low-signal intensity on T1- and 
T2-weighted images (A, B; axial, D, E; sagittal, F, G; coronal). 
Edema of low-signal intensity on T1-weighted and high-signal 
intensity on T2-weighted images can be observed (A, B). The 
tumor has high-signal intensity on T2-STIR (H; coronal). 
Moderate enhancement by Gadolinium (0.2 ml/kg, Magnebist, 
Schering, Germany) is seen on T1-weighted image (C; axial). 
(Siemens Symphony 1.5T, FOV = 200 × 200 mm, matrix = 
256 × 320).
Computed tomography with contrast medium (100 ml, Omnipaque300, Daiichi-Sanky , Japan) shows a well-defined mass in th  gluteus maximus muscle, at the age of 60 years old (A; Toshiba AquilionTM4, 120 kV, 300 mA, 0.5 sec/r) and at the ag  of 65 ye rs ld (B; To hiba, Aqu lionTM64, 120 kV,300 mA, 0.5 sec/r)Figure 1
Computed tomography with contrast medium (100 ml, 
Omnipaque300, Daiichi-Sankyo, Japan) shows a well-defined 
mass in the gluteus maximus muscle, at the age of 60 years 
old (A; Toshiba, AquilionTM4, 120 kV, 300 mA, 0.5 sec/r) and 
at the age of 65 years old (B; Toshiba, AquilionTM64, 120 kV, 
300 mA, 0.5 sec/r).Page 2 of 4
(page number not for citation purposes)
World Journal of Surgical Oncology 2007, 5:88 http://www.wjso.com/content/5/1/88muscle was undertaken. Biopsy was not performed in
order to avoid unnecessary contamination from the pro-
cedure. The resected tumor was composed of alveolar pro-
liferation of carcinoma cells with clear cytoplasm and
small round-shaped nucleoli (Fuhrman grade 2), resem-
bling the previously resected RCC, suggesting metastatic
RCC (Figure 3).
Discussion
Surgical resection of metastatic RCC reportedly improves
the outcome of patients with metastatic RCC, and five-
year survival rates are between 35% and 50% after surgical
therapy for solitary metastasis [3,7]. In the current case,
metastatic RCC to the skeletal muscle was found by
chance during a regular checkup for metastasis using CT
on the abdominal cavity. The metastasis had been over-
looked for several years. The lesion may have been
detected earlier by scanning with a wider range, namely
because there was a metastasis in the adrenal gland, and it
may thus be preferable to always cover the area from the
hepatic dome down to below the symphysis during CT
follow-up. However, generally, it is difficult to detect
metastases to the skeletal muscle, because the area of skel-
etal muscle to be metastasized can vary. Moreover, the
tumors may be painless, and they may go unnoticed when
they are small [8]. As for metastatic RCC to the gluteus
maximus muscle, there have been several previous reports
[9,10].
Another factor which makes a correct diagnosis difficult is
that metastasis sometimes occurs long after primary surgi-
cal treatment. It has been reported that 11% of metastatic
RCC cases occurred more than 10 years after initial diag-
nosis [1]. Distant metastasis to the parotid gland has been
reported 17 years after primary surgery [5] and metastasis
to the skeletal muscle has been reported 15 years after pri-
mary surgery [2]. Therefore, in order to reduce the chance
of overlooking a malignant tumor, the possibility of
metastasis should always be considered for patients with
a history of RCC, even long after primary surgery.
Metastatic RCC to the skeletal muscle must be differenti-
ated from primary soft-tissue tumors. Primary soft-tissue
tumors are more common than metastatic tumors to the
skeletal muscle [8]. Generally, either open or needle
biopsy is necessary in order to make a diagnosis in cases
of soft-tissue tumor. In cases where malignancy is proven
by biopsy, the puncture tract should be excised in order to
avoid tumor seeding. Dissemination due to needle biopsy
is rare. However, this may not be true for possible hyper-
vascular tumors as in the current case. Furthermore, nee-
dle biopsy has the risk that the tip of the needle may
penetrate the tumor, when the tumor is small. MRI fea-
tures of metastatic RCC to the skeletal muscle may show
high-signal intensity on T1- and T2-weighted MRI [7], as
seen in the current case. These signal intensities seem to be
characteristic for metastatic RCC to the skeletal muscle,
even in other previous reports where such points were not
emphasized by the authors [8,11]. We did not perform a
biopsy in the current case, since the MRI features of the
tumor were compatible with metastatic RCC to the skele-
tal muscle.
In the current case, the characteristic features of MRI for
metastatic RCC were beneficial in differentiating it from
primary soft-tissue tumor, because most cases of primary
soft-tissue tumor have low- to iso-signal intensity relative
to the skeletal muscle on T1-weighted images and high-
signal intensity on T2-weighted images. Although lipoma,
hemangioma [12], clear cell sarcoma (malignant
melanoma of the soft parts) [13] and alveolar soft-part
sarcoma [14] are all known to have high-signal intensity
on T1-weighted images, fat-suppression MRI is useful to
differentiate lipoma. It has been reported that hemangi-
oma can be differentiated from other malignant soft-tis-
sue tumors by the existence of lobulation, septation, and
central low-signal intensity [12]. On the other hand, clear
cell sarcoma (malignant melanoma of the soft parts) and
alveolar soft-part sarcoma may be difficult to differentiate
from metastatic RCC on MRI. However, MRI may still be
beneficial in excluding benign tumors of lipoma and
hemangioma from malignant tumors of metastasis RCC,
clear cell sarcoma or alveolar soft-part sarcoma.
The high intensity of hemangioma seems to be related
with the fat component, as is the case with lipoma. Higher
signal intensity on T1-weighted images of clear cell sar-
coma (malignant melanoma of the soft parts) is reported
Typical morphology of a clear-cell renal cell carcinoma (Fuhr-man grade 2), with small round-shaped nucleoli a d abundant clear cytoplasm, with nests of tumor cells s parated y thi -w lled, sinusoidal vascu ar spaces (Hematoxylin d Eosin orig n l agnification ×180)Figure 3
Typical morphology of a clear-cell renal cell carcinoma (Fuhr-
man grade 2), with small round-shaped nucleoli and abundant 
clear cytoplasm, with nests of tumor cells separated by thin-
walled, sinusoidal vascular spaces (Hematoxylin and Eosin 
original magnification ×180).Page 3 of 4
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to be correlated with melanocytic differentiation [13]. We
have no reasonable explanation for the high intensity on
T1-weighted image of alveolar soft-part sarcoma and RCC.
The histological features of these two lesions have similar
aspects of rich cytoplasm. Therefore, there may be some
underlying common molecule, contributing to the high-
signal intensity of T1-weighted images, although we have
no way of knowing this as yet.
It has been reported that angiography shows that RCC
metastatic to the skeletal muscle usually appears as hyper-
vascular lesions [7,8]. The Gadolinium enhancement of
MRI in the current case was mild. Gadolinium is a para-
magnetic metal having a very efficient T1 relaxation mech-
anism. In order to be effective, Gadolinium needs to reach
the tissue. Although the degree of enhancement depends
upon the type of sequence and the delay after contrast
injection, early dense venous drainage [8], due to an arte-
riovenous shunt in RCC [7] might reduce the time for
Gadolinium to reach the tissue in order for it to be effec-
tive, resulting in mild enhancement. It is also possible that
mild enhancement shows actually hypovascularity in the
tumor, or perhaps gadolinium enhancement is simply not
correlated with the degree of vascularity.
Conclusion
In conclusion, we present the case of a 65-year-old man
with metastatic RCC to the gluteus maximus muscle. The
nodule was slowly progressive over 5 years. MRI of meta-
static RCC is characterized by high-signal intensity on T1-
and T2-weighted images which may be beneficial in the
differential diagnosis from primary soft-tissue tumors.
Maintaining a high degree of suspicion of metastatic RCC
is required for patients with a history of RCC.
Competing interests
The author(s) declare that they have no competing inter-
ests.
Authors' contributions
AS drafted the manuscript. TY, KT and ShM participated in
the design of the study and performed. SuM, YO and YH
and conceived of the study. AY and YI participated in its
design and coordination and helped to draft the manu-
script. All authors read and approved the final manu-
script. All authors read and approved the final
manuscript.
Acknowledgements
The patient's family was informed that data from this case would be submit-
ted for publication, and the family gave their written consent.
The English used in this manuscript was revised by Miss K. Miller (Royal 
English Language Centre, Fukuoka, Japan).
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Metastasis to the gluteus maximus muscle from renal cell carcinoma with special emphasis on MRI features

Crossref

Abstract Background The skeletal muscle is an unusual site for metastasis from renal cell carcinoma (RCC). Metastatic RCC must be differentiated from benign primary soft-tissue tumors because aggressive surgical resection is necessary. Case presentation We present the case of a 65-year-old man with metastatic RCC in the gluteus maximus muscle (3.8 cm in diameter) found on enhanced computed tomography (CT) 6 years after nephrectomy. Retrospectively, the small mass (1 cm in diameter) was overlooked 5 years earlier on enhanced CT. Because the growth of the lesion was slow, benign tumor was a differential diagnosis. However, magnetic resonance imaging (MRI) showed that the mass had high-signal intensity on T1- and T2-weighted images (WIs) compared to that of skeletal muscle, with mild enhancement by Gadolinium. The MRI features were unusual for most soft-tissue tumors having low-signal intensity on T1-WI and high-signal intensity on T2-WI. Therefore, under a diagnosis of metastatic RCC, the lesion was resected together with the surrounding skeletal muscle. The histology was confirmed to be metastatic RCC. Conclusion MRI features of metastatic RCC may be beneficial in differentiating it from primary soft-tissue tumor.</p

Metastasis to the gluteus maximus muscle from renal cell carcinoma with special emphasis on MRI features

Abstract

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