Extracranial primitive neuroectodermal tumors (PNET) are described
as small round cell, malignant tumors that have the neural crest
regarded as the most likely progenitor and that arise from outside
the central nervous system(
Other terms used for PNET are peripheral neuroepithelioma, adult
neuroblastoma, and Askin tumor; the latter involving the chest wall
and lung. These tumors are part of the Ewing's sarcoma family of
The peak incidence of PNET occurs within the second decade of life.
Recent studies, however, have described cases of PNET within an
age range of newborn patients to 14-year old patients and for a
median of 1 year of age in a population of 26 patients(
The primary site for PNET is frequently the thorax, either in the
intrathoracic or chest-wall areas(
Other less frequent primary sites are pelvis, retroperitoneum, limbs,
neck, and the paraspinal region( ).
There are few cases of PNET of the kidney reported in the literature.
Moreover, these studies have described PNET of the kidney as a rare
entity( , ).
Cases of PNET usually present metastases to the bones, bone marrow,
and lungs( ).
PNET has been diagnosed with increased precision by immunohistochemical
technique employing the MIC2 monoclonal antibody(
PNET can be confounded with sarcomas and neuroblastomas negative
for urinary catecholamine due to the histopathologic, immunohistochemical,
and cytogenetic similarities found in Ewing's sarcomas( ).
VDK, a 9-year old male patient presented with history of abdominal
pain and increase in abdominal mass around 25 days prior to presentation
and with progressive characteristics. In addition, patient also
presented a loss of weight of 5 kg during this period. VDK was negative
for family history of neoplasia and of morbid events without presenting
any differentiating characteristics.
At physical examination, patient presented with regular overall
clinical status and with pale skin; patient was also eutrophic and
afebrile. Patient abdominal mass was painful to the touch, in flank
topography in the right hypochondrium, firm, and attached to the
right kidney. No other alterations were verified during physical
We carried out laboratory and X-ray examinations. Ultrasonography
and tomography exams of the abdomen indicated voluminous tumoral
mass in the right hypochondrium that was adherent to the kidney,
had heterogeneous echogenicity, and exhibited rough calcification
with approximately 15 x 13 x 14 cm in diameter, thus exceeding the
medial line. Patient presented normal for other additional examinations.
Our patient was submitted to surgical procedure of nephrectomy
and complete tumor resection. The tumor presented the macroscopic
features of a Wilms tumor.
Initial anatomicopathological diagnosis was of a small-cell, malignant
neoplasia infiltrating the kidney (figure 1) with a focus of capsular
invasion, tumor-free vascular and urethral margins, infiltration
of hilar fat by neoplasia, and tumor-free paraaortic lymph nodes.
Figure 1 -
We carried out an immunohistochemical study using the avidin-biotin
peroxidase method. The study showed expansile infiltration into
the kidney by neoplasia constituted of trabeculae and small-cell
colonies, undifferentiated cytoplasm, oval and hyperchromatic nuclei
with rough chromatin, and mitosis. Neoplastic cells were negative
for vimentin, cytocheratin, enolase, and leukocytic antigens but
positive for MCI2 (figure 2). A final diagnosis of PNET was established.
Figure 2 -
Patient was treated according to the P6 protocol suggested by the
Memorial Sloan-Kettering Cancer Center, which consists of seven
courses of chemotherapy with vincristine, doxorubicin, high doses
of cyclophosphamide, ifosfamide, and etoposide(
Patient presented clinical development that was favorable to this
type of treatment despite episodes of intercurrence related to agranulocytosis
as a result of high doses of chemotherapy.
After then months of treatment, patient presented relapse in the
paraspinal cervical region and abandoned treatment.
PNET is a malignant neoplasia uncommonly found in children, it is
highly aggressive and presents high rates of relapse. PNET of the
kidney should be included in the differential diagnosis of renal
tumors, particularly in patients who present with advanced disease
at diagnosis. It is important to distinguish PNET of the kidney
from Wilms tumor since they require different therapeutic conduct
and present different treatment outcomes( ).
As to what concerns the histology of the tumor, it is also important
to include small-cell renal carcinoma in differential diagnosis
of neuroblastoma. PNET of the kidney presents as a small-round-cell
tumor without any tubular or glomerular differentiation and with
possibility of presenting areas with small cell aggregate formation.
In PNET, electron microscopy examination can present neurosecretory
granules and immunohistochemical reactions for neuro-specific enolase,
chromogranin A, synaptophysin, and MIC2 are positive(
Cytogenetic alterations observed for PNET have been described as
identical to those observed for Ewing's sarcoma, sharing a unique
and specific t(11;22)(q24;q12) chromosomal translocation. This alteration
was observed in approximately 90% of patients(
Poor-risk for PNET is indicated by tumor volume more than 100 cm3
and over 5 to 10 cm in extension; metastatic spread to the lungs
or bone marrow; high levels of lactic acid dehydrogenase; and tumors
in adolescents and young adults(
The recommended treatment for PNET is surgical resection of the
tumor associated with chemotherapy and radiotherapy treatment. Current
protocols of chemotherapy indicate the use of courses of high-doses
of cyclophosphamide associated with vincristine and doxorubicin,
alternating with courses of ifosfamide and etoposide(
Centers of reference for oncologic treatment have described the
use of high-dose chemotherapy together with autologous bone marrow
transplantation for improved effectiveness of results( ).
It is understood that the PNET of the kidney may have a different
presentation from other PNETs. The PNET of the kidney is characterized
by aggressive clinical behavior, which in turn makes it similar
to malignant rhabdoid tumor. Though uncommon, PNET of the kidney
should be included in differential diagnosis of childhood and adolescence
kidney tumors. Patients with PNET of the kidney usually present
with advanced disease and have poor response to treatment(