2012, Volume 28, Number 1, Page(s) 076-079
Myxoma of the Renal Sinus: Case Report and Literature Review
Ümran YILDIRIM1, Havva ERDEM1, Ali KAYIKÇI2, Ali Kemal UZUNLAR1, Ali TEKİN2, Mehmet Akif KUZEY1
1Department of Pathology, Düzce University, Faculty of Medicine, DÜZCE, TURKEY
2Department of Urology, Düzce University, Faculty of Medicine, DÜZCE, TURKEY
Keywords: Myxoma, Kidney, Renal neoplasms
Myxoma is a rare mesenchymal tumor and it is mainly seen in
heart and skin. Renal myxoma is extremely rare. To date, eleven
cases of kidney myxomas have been reported in the literature. One
of them is myxoma of the renal sinus. Our case was an 82-year-old
man admitted to our hospital symptoms related to the urinary tract
obstruction. Abdominal computerized tomography revealed a solid,
hypodense mass 9 cm in diameter infiltrating the renal parenchyma
in the renal pelvis. The patient underwent nephrectomy. The resected
kidney contained gelatinous tumor with indistinct borders. The
tumor was composed of slender, bland, spindle-shaped cells with large
amounts of mucoid material. Tumor cells were positively stained with
vimentin, focally stained positive for smooth muscle actin and had
negative reactivity for S-100 protein, epithelial membrane antigen
and pancytokeratin. Herein we report the second case of renal
myxoma arising from the renal sinus.
Renal pelvic tumors represent 5-10% of all the renal tumors.
Almost 90% of these are transitional cell carcinomas1
Mesenchymal neoplasms arising in renal pelvis are fairly
uncommon. Most of these neoplasms originate from
vascular or smooth muscle tissue and eighty-one cases of
benign neoplasms and 40 sarcomas were identified in the
A classification of reported mesencymal neoplasm is
presented in Table I. Although benign mesencymal tumors
are more frequently located in renal pelvis, malignant
tumors are located in ureter2.
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|Table I: Classification of mesenchymal neoplasms of renal
pelvıs and ureter
Myxomas are relatively uncommon soft tissue neoplasms.
This tumor can be found in various sites in the body including the skin, heart, soft tissue, head and neck.
Myxoma of the kidney is extremely rare. To date, eleven
cases of pure myxoma reported in the literature (Table II).
Only one of them originated in renal pelvis and others were
situated in renal parenchyma and capsule. Our case is the
second renal myxoma arising in the renal sinus.
An 82-year-old male patient was admitted with the
complaints of dysuria, flank pain and urinary obstruction
for two years. He had been treated with the diagnosis of
tuberculosis and had no urinary system complaints before.
His physical examination was unremarkable. Laboratory
values were within the normal limits. Abdominal USG
revealed a mass, 9 cm in diameter, solid with heterogeneous echo in the left renal pelvis. CT scan showed a low density
mass (Figure 1
). Fine needle aspiration was performed
and resulting suspicious cytology for malignancy. Patient
underwent a left radical nephrectomy.
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|Figure 1: Computed Tomograhy image without contrast media
in prone position showing hyperdense biopsy needle entering
hypodense mass in the left kidney.
Nephrectomy specimen weighed 330 g together with
perirenal fat tissue. On sagittal section, the pelvis of the left kidney contained a 9x6x5 cm semitranslucent, gelatinous
tumor mass. Tumor involved the renal parenchyma. Other
pathologic findings such as calculi, hidronephrosis were
not detected on gross examination of the renal tissue
(Figure 2). Microscopically, the tumor was composed of
hypocellular and hypovascular myxoid stroma. Tumor
cells were spindle, fibroblast like, oval and stellate shaped.
Nuclear atypia and mitosis were not demonstrated
(Figure 3). Tumor was invading renal parenchyma. The
tumor and renal parenchyma were indistinct. Ureter was
intact. There was no pathological finding in non-tumoral
areas. The myxoid stroma was stained with alcian blue and
tumor cells were positively stained with vimentin (Figure 4), focally stained positive with smooth muscle actin
(SMA), and negatively stained for S100 protein, epithelial
membrane antigen (EMA), and pancytokeratin. Final
diagnosis was myxoma of the renal sinus according to
gross, microscopic and immunohistochemical findings.
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|Figure 2: Tumor tissue 9 cm in diameter demonstrated in the left
kidney. The surface of the greenish mass had a semitranslucent
appearance and the mass was composed of a gelatinous, stringy
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|Figure 3: Photomicrograph shows tumor tissue including
scattered stellate cells in the myxoid material (H&E, x200).
Various benign mesenchymal tumors of the renal pelvis
have been reported in the literature1-3
. Some of these
are hemangioma (40 cases), leiomyoma (10 cases),
schwannoma-neurofibroma (2 cases), solitary fibrous
tumor (2 cases), glomus tumor (1 case). Malignant
mesenchymal tumors composed approximately 30% of
mesenchymal neoplasms arising in renal pelvis1-3
total of 38 malignant mesencymal tumor cases have been
reported in the literature up to date. Ninety percent of these
are smooth muscle origin. These include leiomyosarcoma
(12 cases), malignant schwannoma (1 case), angiosarcoma,
osteosarcoma, chondrosarcoma and rhabdomyosarcoma1-3
. Myxoma has not been situated in classification of
mesenchymal tumors of the kidney in textbooks yet.
Myxoma has been described first by Virchow in 18634-6.
Although myxomas show similar microscopic appearance,
they exhibit different behavioral and clinicopathological
course4-6. It is suggested that this difference is based on
Myxomas located in different sites of the body have different
molecular mutations and other abnormalities4-6.
Cells of myxoma considered to be originated from
fibroblast like primitive mesencymal cells. These cells are
similar to fibroblast but they lost the capacity to polymerize collagen. Some authors believe that myxoma is a myxoid
change of some mesenchymal tumors such as leiomyoma
and degenerative changes seen in adipose tissue in brown
atrophy of the heart7-9. The others believe that the
uniform cellular component throughout the lesion supports
a neoplastic nature rather than a regressive change within
the pre-existing tumor7-9.
Clinicopathological data of the reported twelve cases are
shown in Table 2. Data were available in ten of the twelve
cases including our case3,4,7-13. Six of the patients were
male and the age at the diagnosis ranged from 27 to 82 years
(mean 51,3). Our case is the most elderly one among these
cases. Tumor size varied from 4 to 28 cm (mean 12,2 cm).
Tumors were located in lower pole of the kidney in four
cases, upper pole in one case, entire kidney in one case
and middle pole in three cases except the case reported by
Nisimoto K in 1996. Our case is the second one located in
Histopathologic appearance of renal myxomas resembles
others located at different sites of the body. The present case
showed similar cellular structure with myxoma with the
lack of pleomorphism, mitosis and nucleoli.
Renal myxoma should be differentiated from other
benign and malignant mesenchymal tumors such as
myxoid neurofibroma, myxoid leiomyoma, perineuroma,
myxolipoma, myxoid variant malignant fibrous histiocytoma,
liposarcoma, leiomyosarcoma and rhabdomyosarcoma.
Renal myxoma can be easily distinguished from sarcoma
with the lack of anaplastic features in nephrectomy material.
Each benign tumor display characteristic histopathological
and immunohistochemistry features8,11,12. Our case
did not have different histological areas such as neural,
fibrous, leiomyomatous changes.
The present case was focally stained positive with SMA
which reminded leiomyoma possibility in the differential
diagnosis. However, specimens which were taken from the
tumor did not show any fasciculated spindle cells or bundles
that were specific for leiomyoma. Homogeneous structure
throughout the sections, focal positive staining with SMA,
desmin negativity and loss of parallel alignment of the
cells also withdrew us from the diagnosis of leiomyoma16. Our case also differed from myxoid liposarcoma with
the lack of lipoblastic differentiation and differed from
myxoid lipoblastoma with the lack of atypia, characteristic
multilobular pattern and existence in the elderly17,18.
Cytopathological examination can be performed to
distinguish benign tumors from malignancies. We have
performed fine needle aspiration accompanied with
CT before the surgical procedure and the result showed
In conclusion, we described here a very rare type of mesenchymal
tumor of the renal sinus. It is important to distinguish
this benign entity from malignant tumors that may
exhibit secondary myxoid changes due to overtreatment.
The treatment of choice is radical nephrectomy. A case
cured with enucleation was also reported in the literature
but this was not possible in our case due to infiltration of
the surrounding renal parenchyma.
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