Rhabdomyosarcoma, [s8]uncommon

Rhabdomyosarcoma is the commonest soft tissue sarcoma in Africa. It occurs more often in males than in females, usually between 5 and 25 years in: (1) The head and neck especially the orbit (25%). (2) The bladder[md]sarcoma botryoides (''grape-like') (30%). (3) The trunk (10%) and the limbs (10%). (4) The testis.

Rhabdomyosarcomas probably arise from embryonic mesenchymal tissue and are fairly malignant. They spread locally quite rapidly; lymphatic spread is rare, and distant spread through the bloodstream is late. Although previously considered to be tumours of striated muscle, they are now classified as hamartomas.

In sites other than the bladder or prostate, a rhabdomyosarcoma presents as a painless swelling which grows fairly rapidly; in the bladder and prostate it presents as a suprapubic mass, which you can confuse with a full bladder.

RHABDOMYOSARCOMA DIAGNOSIS. Biopsy a large mass and do an excision biopsy of a smaller one[md]except in the bladder. There, establish the diagnosis with an IVU, cystoscopy, and a cystogram.

THE DIFFERENTIAL DIAGNOSIS includes inflammatory masses (pyomyositis, etc.), a haematoma, and other tumours. In the orbit consider other causes of proptosis[md]an orbital mucocele, retinoblastoma, etc. (24.11). In the suprapubic region consider a full bladder or tuberculous lymphadenopathy.

STAGING. The stage and differentiation of a rhabdomyosarcoma are more important than its histological type (embryonal, alveolar, etc.).

Stage I A localized tumour which has been resected completely.

Stage IA A tumour confined to muscle or to the organ of origin.

Stage IB The tumour extends beyond the muscle or organ of origin.

Stage II Regional disease which has been completely resected macroscopically.

Stage IIA Residual disease microscopically.

Stage IIB Nodal disease or involvement of an adjacent organ or structure.

Stage III Incomplete resection macroscopically.

Stage IV Distant metastases.

MANAGEMENT. Without treatment the disease progresses rapidly. Surgery is the main treatment. Radiotherapy following it does not increase the disease-free survival rate, but chemotherapy (actinomycin D with vincristine for one year) does, and 3 year survivals for orbital tumours of 90% and for bladder tumours of 30% are recorded.

If you are not sure of the diagnosis do a simple biopsy. Developing or resolving pyomyositis may need to be excluded this way.

If a mass is small ([lt]5 cm) do an excision biopsy. Remove the entire tumour with 2 or 3 cm of normal tissue all round. Very radical surgery does not improve the prognosis.

If you yourself cannot remove the tumour entirely, but think that surgery might be possible, as in the bladder, refer the patient.

CHEMOTHERAPY. Combined actinomycin D and vincristine for one year is a useful addition to surgery, when you know the histolology. His prognosis is poor, so other malignant tumours should have priority. Long-term survival of deep-seated tumours (especially of the genitourinary tract and trunk) is unusual. Orbital tumours have the best prognosis. A suitable regime is actinomycin D 1 mg/m['2] on days 1 and 3, with vincristine on day 1, repeated every 3 weeks up to 6 courses, then every 6 weeks.