Spindle cell rhabdomyosarcoma in adults

Spindle cell rhabdomyosarcoma is a recognised variant of embryonal rhabdomyosarcoma of children2. In children, it occurs mainly in the paratesticular area of boys and has a relatively good prognosis2. A few cases of spindle cell rhabdomyosarcoma have been reported in adults1.

Epidemiology

Less than 10% of adult rhabdomyosarcomas are of spindle cell type. There is a 2:1 male predominance with a wide age range. There is no association with neurofibromatosis. Lesions most commonly occur on the head and neck, but are found at a wide range of sites, including the diaphragm6, paratesticular area3 and uterus4.

Histopathology

The tumours show infiltrating margins. There is a cellular proliferation of spindle cells with pale cytoplasm in long intersecting fascicles. Most cells are spindled with small nuclei and inconspicuous nucleoli. In addition, there are scattered spindled or polygonal rhabdomyoblasts with hyperchromatic eccentric nuclei and abundant eosinophilic cytoplasm. In some tumours, the rhabdomyoblasts are focally numerous. Necrosis may be seen. In some cases, sclerosis divides the tumour cells into small nests and creates a pseudovascular appearance5.

Immunohistochemistry

	Desmin	16/16(diffusely positive in all cases)1, 7/77
	Myogenin	12/121
	Fast myosin	7/91, 2/77
	Myoglobin	2/31, 1/14
	SMA	11/141, 5/7(focal)7
	HHF35	9/91
	myf4	7/77
	Sarcomeric actin	1/14
	Myo-D1	1/14
	AE1/AE3	1/?(focal positivity)1
	EMA	1/?(focal positivity)1, 0/77
	Caldesmon	0/?1, 0/77
	S-100	0/?1, 0/26, 0/77
	GFAP	0/?1
	WT1	7/77
	CD99	7/77
	CD34	0/77
	Pancytokeratin	0/77

Ultrastructure

Rhabdomyoblasts show sarcomeric differentiation6.

Differential diagnosis

Spindle cell carcinoma: positive for cytokeratins but negative for muscle markers.
Desmoplastic malignant melanoma: positive for S-100 and melanoma markers but negative for muscle markers.
Leiomyosarcoma: nuclei are cigar-shaped: cytoplasmic is eosinophilic but rhabdomyoblasts are absent: positive for caldesmon but negative for myogenin.
Malignant peripheral nerve sheath tumour with rhabdomyosarcomatous differentiation (malignant Triton tumour): arises from large nerves: associated with neurofibromatosis type I: variably positive for and focally for muscle markers.
Adult fibrosarcoma: negative for muscle markers.

Management

Aggressive treatment including specific chemotherapy.

Prognosis

Patients may have uncontrollable local disease, local recurrences or metastases. The outcome is worse than for childhood spindle cell rhabdomyosarcoma but is better than for pleomorphic rhabdomyosarcoma of adults.

References

1 Nascimento AF,Fletcher CD. Spindle cell rhabdomyosarcoma in adults. Am J Surg Pathol 2005; 29:1106-13

2 Cavazzana AO, Schmidt D, Ninfo V, et al. Spindle cell rhabdomyosarcoma. A prognostically favorable variant of rhabdomyosarcoma. Am J Surg Pathol 1992; 16:229-35

3 Kizer WS, Dykes TE, Brent EL, et al. Paratesticular spindle cell rhabdomyosarcoma in an adult. J Urol 2001; 166:606-7

4 McCluggage WG, Lioe TF, McClelland HR, et al. Rhabdomyosarcoma of the uterus: report of two cases, including one of the spindle cell variant. Int J Gynecol Cancer 2002; 12:128-32

5 Mentzel T,Katenkamp D. Sclerosing, pseudovascular rhabdomyosarcoma in adults. Clinicopathological and immunohistochemical analysis of three cases. Virchows Arch 2000; 436:305-11

6 Rubin BP, Hasserjian RP, Singer S, et al. Spindle cell rhabdomyosarcoma (so-called) in adults: report of two cases with emphasis on differential diagnosis. Am J Surg Pathol 1998; 22:459-64

7 Mentzel T, Kuhnen C. Spindle cell rhabdomyosarcoma in adults: clinicopathological and immunohistochemical analysis of seven new cases. Virchows Arch. 2006 Nov;449(5):554-60.

This page last revised 30.3.2010.