Discussion
Thymic neoplasms are very rare tumours in pediatric patients. Present
literature concerning thymic tumours is mostly comprised of single case
reports with only few larger series [2-9]. Diagnosis, as in adults,
is made after biopsy or tumour resection, but could be difficult due to
the rarity of this tumour in pediatric population. Differential
diagnosis of mediastinal mass usually reveals lymphoma or neurogenic
tumours [4]. Patients presents with nonspecific symptoms of airway
obstruction which was also observed in our study although not all of the
patients had disease signs [1-9]. None of children presented with
myasthenia gravis, but the coexistence of it with thymoma in children is
less frequent with incidence of 7 to 15% [2,3,14,15]. WHO
histopathological classification and Masaoka-Koga staging systems are
the basis for treatment choice in adults as well as in children
[10-12].
Fonseca AL. et al. in her report described the results of thymic tumours
in children and found that this tumours presents more often in male but
our group shows no sex predominance [15]. The largest study of
Stachowicz-Stencel of 36 thymoma and thymic carcinoma patients showed
male predominance – 21 male vs 15 female patients, also Rod J. in his
literature analysis found male predominance in pediatric thymoma
population [2,3]. Median age of patient described in our study is
younger than reported in literature (median 12 years old) [2,3].
Surgery, possibly with R0 resection, remains the gold standard for
treating all thymic neoplasms. CTH and RTH are used in patients with
large or inoperable tumours, in the presence of metastases or after
non-radical resections [1-3,5-9] (Table 5). Thymic carcinoma carries
more poor prognosis and chemoradiotherapy is often offered after
resection [2,3,6]. RT doses used in other studies usually are within
the range of 40 to 54 Gy, which corresponds to the total doses used in
majority of our patients [1-9]. Very young age could be the reason
for implementing doses below 40 Gy in our group. A report from the
European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT)
written by Stachowicz-Stencel T. et al described results of 16 patients
with thymoma and 20 with thymic carcinoma [2]. Only one child with
thymoma received RTH and at the end of median follow-up of 5 years only
2 patients (12.5%) died due to the disease. Cisplatin was the most
commonly used systemic agent, but only 4 patients received CTH. What is
important, radical surgery (R0) was achieved in 11 of them and was the
only treatment in those patients. Thymic carcinoma patients in majority
had only biopsy (80%), received CTH (70%) and RTH (60%) with total
dose of 38 to 54 Gy which could translate into such poor results of
5-year OS of only 21% [2]. The same observation could be made based
on Ramon y Cajal S et al. study with median survival of patients with
thymic carcinoma of only 8 months [8]. Also Rod et al. in the report
from French Society of Pediatric Oncology observed poor results in
patients with thymic carcinoma [3]. The patient with thymic
carcinoma included in our analysis had radical surgery and received
postoperative RTH to 44 Gy which resulted in 74-month free of disease
follow-up.
The limitations of our study are like in all studies on rare tumours - a
retrospective study covering a long time period with different treatment
modalities. Although, due to the rarity of this tumour in pediatric
population, studies like ours are the only way to collect the experience
in this topic.
Combined treatment, including surgery, chemotherapy and radiotherapy
could provide satisfactory results in thymoma patients. There is need
for further larger multi-national or institutional analysis with
long-term follow-up which can help to provide more information for
optimal management strategies and outcome.
Conflict of interest : The authors declare that the research was
conducted in the absence of any commercial or financial relationships
that could be construed as a potential conflict of interest.
Authors’ contributions : Conceptualization, A.N., L.M.;
methodology, A.N.; software, A.N.; formal analysis, A.N.; investigation,
A.N.; resources, A.N.; data curation, A.N.; writing—original draft
preparation, A.N.; writing—review and editing, A.N., L.M..;
visualization, A.N.; supervision, L.M. All authors have read and agreed
to the published version of the manuscript.
Acknowledgment: Not applicable.