Primitive (polypoidal) non-neural granular cell tumour of the skin

Definition

A rare skin tumour with granular cytoplasm that is not a granular variant of another tumour type and lacks evidence of neural differentiation: in particular, there is negativity for S-100.

Epidemiology

Tumours are found equally in men and women, occurring in children and young adults.

Clinical features

Lesions are solitary and occur predominantly on the back but may be found on the head or limbs.

Radiology

Macroscopic appearances

Tumours are located in the dermis. If superficial, there may be an epidermal collarette. Deeper lesions extend into the subcutis.

Histopathology

The tumours are well circumscribed but not encapsulated. Cells may be spindled, ovoid or polygonal. There is abundant granular cytoplasm. The nuclei are vesicular and may have a single small prominent nucleolus. The cells form diffuse sheets. There may be entrapped skin adnexa.

Immunohistochemistry

NKI-C3 and CD68 are non-specific markers of the presence of lysosomes.

	NKI-C3	11/121
	CD68	7/111, 1/33
	NSE	5/101
	Vimentin	2/33
	S-100	0/131, 0/43
	SMA	0/121
	Desmin	0/121, 0/23
	Muscle-specific actin	0/33
	Pancytokeratin	0/111, 0/23
	EMA	0/81
	CEA	0/23
	Cathepsin-B	0/23
	alpha-1-antichymotrypsin	2/33
	Factor XIIIa	1/23
	Mac387	0/23
	MBP	0/23
	LCA	0/91

Ultrastructure

The cells contain lysosomal granules and cytoplasmic filaments indistinguishable from those of conventional granular cell tumours.

Differential diagnosis

Conventional granular cell tumour has poorly defined margins. The polygonal cell population has small eccentric hyperchromatic nuclei. They are immunoreactive for S-100 as well as NSE and CD68. The cells contain numerous lysosomes which usually contain dense amorphous material. An external lamina surrounds cells.
Granular variant of leiomyoma or leiomyosarcoma3 have cigar-shaped nuclei and are positive for SMA, desmin and caldesmon. The lesion is centred in the reticular dermis3.
Granular variant of benign fibrous histiocytoma.
Atypical fibroxanthoma
Fibrous papule of the face
Naevus or melanoma with granular cell change is positive for S-100, MART-1, MITF and HMB45
Granular variant of basal cell carcinoma shows peripheral palisading and is positive for cytokeratins3.
Granular variant of skin adnexal tumours are positive for cytokeratins.
Congenital CD34-positive granular cell dendrocytosis: negative for S-1002.
Metastatic renal cell carcinoma is positive for cytokeratins and EMA.
Congenital epulis of the newborn is an oral lesion, negative for S-100.

Prognosis

Lymph node metastases have been reported in one case1.

References

1 Lazar AJ, Fletcher CD. Primitive nonneural granular cell tumors of skin: clinicopathologic analysis of 13 cases. Am J Surg Pathol 2005; 29:927-34

2 Chang SE, Choi JH, Sung KJ, et al. Congenital CD34-positive granular cell dendrocytosis. J Cutan Pathol 1999; 26:253-8

3 LeBoit PE, Barr RJ, Burall S, et al. Primitive polypoid granular-cell tumor and other cutaneous granular-cell neoplasms of apparent nonneural origin. Am J Surg Pathol 1991; 15:48-58

This page last revised 9.9.2005.