Alveolar soft part sarcoma is a rare soft tissue malignant
neoplasm that affects young people. It can present in any
region of the body, having been described from the tongue
[1]
to the sacrum
[2]
and is most commonly seen in the
trunk and the extremity
[3-5]
. Often indolent, the primary
tumor may grow for years before medical attention is
sought. Widespread metastases are frequent.
The tumor received its name owing to its pseudo-alveolar
histological appearance, characterized by cells arranged in
clusters with a loss of central cohesion. It is a highly
vascularized tumor with small vascular spaces interdigitating
between nests of cells. On electron microscopy, the cells of
alveolar soft part sarcoma contain characteristic, electron-
dense polygonal crystals in the cytoplasm (
Fig. 1
)
[6]
, which
contain complexes of the proteins monocarboxylate trans-
porter 1 and CD147
[7]
.
This retrospective study of children, adolescents, and
young adults sought to define the clinical presentation,
methods of diagnosis, treatments used, and results obtained
for young people seen at a major cancer center with alveolar
soft part sarcoma. We reviewed a 30-year, single-institution
experience with young patients with this disease. To
recapitulate the modes of presentation likely to be encoun-
tered by pediatricians and pediatric surgeons, we looked
solely at patients who were younger than 25 years old at the
time of diagnosis.
1. Methods
A waiver of authorization (WA0374-04) was obtained
from our institutional review board, in compliance with
institutional and Health Insurance Portability and Account-
ability Act standards. We identified patients from all institu-
tional databases treated at The Memorial Sloan-Kettering
Cancer Center for alveolar soft part sarcoma who were
younger than 25 years old at the time of diagnosis and who
were treated between 1974 and 2004. All patients had
pathology reviewed at our institution. Medical records,
operative notes, pathology and radiology reports, and
correspondence that was part of the medical record were
used as primary source data. Follow-up data were obtained
from notes and correspondence in the medical record. No
patients were contacted for supplemental data.
Extent of disease was classified retrospectively according
to the Intergroup Rhabdomyosarcoma Study (IRS) clinico-
pathologic grouping system (group I­group IV), and TNM
grouping was assigned according to standard published
criteria
[8]
. Clinicopathologic assessment of tumor size and
invasiveness was made using available data from pathology
reports, preoperative radiology, and operative notes. Patient
12 presented after grossly incomplete tumor excision, and we
estimated the size of the initial tumor by adding the diameter
of tumor excised to the residual disease seen on imaging.
Time to progression was measured from the date of
diagnosis to the date of pathological confirmation or, when
not resected, to the date of the first radiological indication of
progressive disease. For 1 patient (#19), brain metastases
were diagnosed at an outside hospital during 1984, but the
precise date could not be ascertained, so progression was
estimated to occur at the midpoint of that year. Probability
estimates of 5-year overall follow-up and progression-free
follow-up were obtained by the product limit method
[9]
,
and differences between time to progression between groups
were evaluated using log-rank statistics
[10]
.
2. Results
2.1. Clinical presentation
Twenty patients (10 male, 10 female) with a median age
at diagnosis of 16.5 years (range 6-24) were identified
(
Table 1
). The most common presentation was a mass (n =
17), accompanied by pain (n = 4), numbness (n = 1), and
nausea and vomiting (n = 1).
The most common site for the primary sarcoma was the
thigh (n = 8). This was followed by the trunk (n = 6), the
retroperitoneum (n = 2), and the scalp, neck, forearm, and
calf (n = 1 each). Primary tumor size, known in 13 of
20 patients, averaged 6.5 cm (range 2.4-15). Vascular
invasion was specifically noted by the pathologist in 6 of
the primary tumors (30%).
At the time of diagnosis, regional spread was present in
2 patients: a thigh lesion had eroded into the femur in one, and
a neck primary had spread to a neck node and submandibular
gland in the other. Distant metastases were seen in the lungs
of 7 of the 20 patients at initial presentation. Among these,
2 had brain metastases at presentation as well.
Reverse transcriptase­polymerase chain reaction, which
can detect the ASPL-TFE3 fusion transcripts characteristic
Fig. 1
Magnetic resonance image of an alveolar soft part sarcoma
in the vastus lateralis muscle. (inset), Electron micrographic view of
the intracellular crystals in the tumor.
M.L. Kayton et al.
188