Baylor University Medical Center Proceedings April 2017 - 207

is also positive for diﬀerent neural
biomarkers such as S-100, Leu 7,
and NSE (13). The immunohistochemistry ﬁndings are further
supported by the identification
of a characteristic EWSR1⁄FLI1
fusion product that results from
a t(11;22) (q24⁄q22;q12) translocation. This translocation is
identiﬁed in 90% of cases and unequivocally conﬁrms the diagnosis (7, 14). Among our cases, IHC
details were available in 5 patients,
and all were positive for CD99.
Renal PNET appears to be a
unique clinical entity that behaves
more aggressively than PNET arisFigure 2. (a) Hematoxylin and eosin stain (40×) showing the neoplasm composed of large nests of cells with a moderate
amount of cytoplasm, moderately pleomorphic nuclei with granular chromatin, and areas of geographic necrosis, with ing at other sites. As the tumor is
highly aggressive, it is often diagthin vascular channels in between. Scattered mitosis was seen. (b) MIC-2 (CD99) shows strong membrane positivity.
nosed in an advanced stage when
it has already involved perinephric
fat, hilar lymph nodes, renal veins, and the inferior vena cava.
involvement. Technetium-99m scintigraphy is useful for the
In more advanced stages, the tumor involves the liver, spleen,
detection of bone metastases (6). CT imaging details were availperitoneum, and lungs. The prognosis for renal ES ⁄ PNET is
able in 5 of our cases and showed mass lesions arising from the
upper or lower poles of the kidney, 3 with calciﬁcations.
generally poor, with a 5-year disease-free survival of 45% to
Diagnosis of renal PNET is challenging. Although radio55% in localized cases, whereas cases with an advanced stage at
logical features may be suggestive, biopsy with immunohistopresentation have a median relapse-free survival of only 2 years
chemistry is required to conﬁrm the diagnosis. Renal PNET is
(9, 13, 15).
characterized by small uniform round cells with dark nuclei,
The treatment for renal ES ⁄ PNET is similar to that for
ill-deﬁned cytoplasmic borders, and poorly formed rosette-like
ES/PNET elsewhere and includes surgery, chemotherapy,
structures (9). The histopathologic features overlap with other
and radiation (6, 10). Surgical options include partial or total
small round blue cell tumors like neuroblastoma, desmoplastic
nephrectomy with cavotomy in cases of renal vein involvement
(6, 14). The diagnosis of renal ES ⁄ PNET is often made postsmall round cell tumor, and lymphoma. Immunohistochemoperatively and hence chemotherapy is generally given as an
istry and molecular studies play a crucial role in diﬀerentiatadjuvant. The recommended chemotherapy regimen is vining these tumors. PNET shows strong positivity for MIC-2
cristine, doxorubicin, and cyclophosphamide alternating with
gene product and CD-99 over the membrane of tumor cells,
ifosfamide and etoposide given for a period of 1 year (16).
which is seen in more than 90% of renal PNET cases (7). It
The role of radiotherapy is not clear,
but it may be given in locally adb
a
vanced disease and in those with
positive margins. Despite aggressive therapy, the overall cure rate
of renal PNET is only 20% (17).
Among the 7 cases reported here,
6 underwent radical nephrectomy,
5 received chemotherapy, and 4
received radiation therapy. Four
patients were alive beyond 1 year,
and one is alive in remission at 15
months. The survival of our patient
group ranged from 6 months to 18
months. Since the overall prognosis
of this tumor is poor, an early and
accurate diagnosis is crucial for the
Figure 3. Contrast-enhanced CT of the abdomen showing a large irregular heterogeneously enhancing mass lesion proper management of these aggressive tumors.
arising from the upper pole of the right kidney, with multiple specks of calcification within.
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