DISCUSSION
Soft tissue sarcomas (STS) in children are rare tumours, approximately
1000 cases are diagnosed annually in the United States of
America.11,12 These tumours are heterogenous in nature
and can occur in any part of the body.13 This study
documented 112 paediatric soft tissue sarcomas over a 26 year period,
representing roughly 4.3 cases every year. This result is similar to an
earlier reported figure of 4.7 per year from our centre. This study
however differs with Dauda et al. (Jos Nigeria) and Kachanovet al. (Moscow) who reported 8.9 and 6.8 per year respectively in
children less than 15 years of age.14–16 This
difference can be attributed to different study intervals. The studies
by the afore mentioned authors (Dauda et al. and Kachanovet al. ) each covered a 10-year period compared to this present
study. Another reason for this difference may be due to different
disease demographics among different study populations.
Soft tissue sarcomas (STS) are classified broadly into
Rhabdomyosarcomas( RMS) and non-rhabdomyosarcomas (NRMS) otherwise
termed non-rhabdomyosarcoma soft tissue sarcomas
(NRSTS).1,11 Most studies report rhabdomyosarcoma
(RMS) as the commonest paediatric STS similar to this
study2,11,15–17 The predominance of embryonal and
alveolar RMS supports the childhood occurrence of these sarcoma subtypes
while the very few pleomorphic RMS supports the rare occurrence of these
tumours in children.12,13 Other adult-type STS seen in
this study differ somewhat in spectrum from those seen
elsewhere.18 Leiomyosarcoma and liposarcoma reported
by Ferrari et al . were not seen in this
study.18 Also, Ferrari et al. reported synovial
sarcoma as the commonest NRSTS tumours, accounting for 34% of their
cases contrary to vascular sarcomas seen in this study as the commonest
NRSTS.18 Other researchers have documented other
sarcoma subtypes as being the commonest among the NRSTS supporting the
heterogeneity of these tumours.1 Occurrence of these
NRSTS in the paediatric age suggests similar yet to-be identified
etiologic factors.
No difference in tumour occurrence was seen between male and female
gender in this study suggesting a common pathogenetic pathway. Studies
have suggested genetic alterations such as Li Fraumeni syndrome and
exposures to radiation as possible causes of RMS while the causes and
risk factors for NRSTS are not known.11 The modal age
in our study differs from those of Dauda et al. in Nigeria and
Kachanov et al. in Moscow which documented older age
groups.15,16 This difference is due to the differences
in distribution of tumour subtypes across the age groups in these
studies. In the study by Kachanov et al . RMS constituted 23% of
tumours in the age group 10-14 years while the NRSTS tumours were
predominant in this age group although RMS accounted for 54.4% of all
the STS.16 Likewise, alveolar RMS and Embryonal RMS
occurred with higher frequency in the age group 12-15 years in the study
by Dauda et al , compared to the 5-9 years seen in this present
study.15
Anatomic location for STS varies in different studies. We documented
head and neck as the commonest location. This is in contrast to Daudaet al . whose study reported extremities as the commonest
location.15 This may suggest different pathogenesis.
For example, embryonic cell arrest during migration in caudal-cephalad
direction with malignant transformation may explain the higher frequency
of embryonal and alveolar rhabdomyosarcoma in such regions.
The known prognostic factors for STS we studied include tumour size,
grade and stage, histological subtype and location. Ferrari et
al . found among NRSTS, increasing tumour depth and size to be more
strongly predictive of survival among children compared to their adult
counterparts.18 Deep tumours and tumour size greater
than 5cm were associated with poorer survival while tumours of the head
and neck showed better survival.18 Tumour size not
only determines tumour burden but also surgical resection as a modality
of treatment and this factor affects tumour
recurrence.12 Rhabdomyosarcomas are by their nature
high grade tumours although very chemo- and
radiosensitive.13 Overall, most STS in this study were
of high grade status. The mean tumour size of 7.4cm, higher frequency of
grade 3 tumours and tumour stage suggests worse prognosis for tumours
seen in our practice environment. On the other hand, the higher
frequency of head and neck location of STS might suggest a favourable
prognosis in addition to the predictability of response to therapy if
offered to these patients.12 Patients with deep
tumours or tumour size >5cm may therefore need to be
treated with multimodal approach.19
Absence of follow up data in this study has made it difficult to examine
the effects the poorer clinicopathological parameters with patient
overall survival. Prospective studies should incorporate data on
adjuvant therapies and survival as these may suggest additional
biological behaviours of tumours in our environment.