Rhabdomyosarcoma is a mesenchymal sarcoma derived from primary muscle cells (rhabdomyoblasts) and represents 3- 5%of malignant solid tumors in childhood.
Among the extracranial solid tumors of childhood,
RMS is the third most common neoplasm after neuroblastoma and Wilms’ tumor.
There is a slight male predominance,
with a peak incidence during the first 5 years of life.
Members of families with Li-Fraumeni syndrome,
children with Beckwith-Wiedemann syndrome,
neurofibromatosis and Costello syndrome have a high risk of developing rhabdomyosarcoma.
Children between the ages of 1 and 9 tend to have a better prognosis than children 10 and older or younger than 1.
RMS can arise virtually anywhere in the body,
including sites where striated muscle is not normally found.
The most common RMS sites in children include: head and neck (35%),
urinary and reproductive organs (excluding the bladder and prostate gland) (14%),
limbs (14%),
bladder and prostate (7%).
RMS is subclassified into three basic histologic subtypes:
- embryonal,
- alveolar and
- pleomorphic.
Alveolar tumours tend to be more aggressive and have a poorer prognosis than embryonal tumours.
Fig. 1
The symptoms of rhabdomyosarcoma may vary depending on the location of the tumour.
- When the tumor is in the trunk,
extremities,
or groin,
the first sign is usually a mass or swelling that often doesn't cause any pain or other problems.
- Tumors around the eye cause the eye to bulge or the child to appear to be cross-eyed.
- When it is in the ear or nasal sinuses,
rhabdomyosarcoma can mimic an earache or a sinus infection.
- Tumors in the bladder and vagina may bleed or grow big enough to make it difficult or painful to urinate or have bowel movements.
- Tumors in the abdomen or pelvis can cause vomiting,
abdominal pain,
or constipation.
- Rhabdomyosarcoma rarely develops in the bile ducts,
but when it does it can cause yellowing of the eyes or skin.
The clinical group is based on the extent of the disease and how completely it is removed during initial surgery:
Group I: This group includes children with localized disease (the cancer has not spread to nearby lymph nodes or to distant sites in the body) that is completely removed by surgery.
Group IA: Children in this group had a tumor that was still confined to the muscle or organ where it started and was completely removed by surgery.
It had not spread to nearby lymph nodes or distant sites.
Group IB: Children in this group had a tumor that had grown beyond the muscle or organ where it started and into nearby structures,
but it was completely removed by surgery.
It had not spread to nearby lymph nodes or distant sites.
About 15% of rhabdomyosarcoma patients are in group I.
Group II: This group includes children who have had tumors that have been removed by surgery,
but cancer has been found around the edges of the removed specimen,
in the lymph nodes or in both places.
In all cases,
as much of the cancer has been removed as possible.
Group IIA: The cancer has not spread to nearby lymph nodes or elsewhere.
The surgeon has removed all the cancer that could be seen,
but the pathologist has found cancer at the edge of the removed specimen,
which means that there is a small amount of cancer left behind.
Group IIB: The cancer has spread to nearby lymph nodes,
but all of the cancer has been removed by surgery.
Group IIC: The cancer has spread to nearby lymph nodes.
The surgeon has removed all the cancer that could be seen (including in the lymph nodes),
but the pathologist has found cancer at the edge of the removed specimen,
which means that there is a small amount of cancer left behind.
About 20% of patients are in group II.
Group III : These children have tumors that cannot be completely removed,
leaving some tumor behind that can be seen with the naked eye.
The tumor may have spread to nearby lymph nodes,
but there is no sign that it has spread to distant organs.
Group IIIA: The tumor cannot be completely removed by surgery,
and only a biopsy of the tumor has been done.
Group IIIB: The tumor cannot be completely removed,
but surgery has removed at least half of the tumor.
This group accounts for about 50% of patients with rhabdomyosarcoma.
Group IV: These children have evidence of distant spread at the time of diagnosis to places such as the lungs,
liver,
bones,
bone marrow,
or to distant muscles or lymph nodes.
The TNM stage depends on the type and size of the tumor,
its invasion of the lymph nodes and distant organs,
and where it starts.
It is based on 3 key pieces of information:
T: the characteristics of the tumor
N: whether the cancer has spread to nearby lymph nodes
M: whether it has metastasized (spread) to distant parts of the body.