Interdigitating dendritic cell tumour/sarcoma, reticulum cell sarcoma

Definition

A neoplasm of spindle to oval cells with the phenotype of interdigitating dendritic cells.

Equivalent normal cell

Interdigitating dendritic cells are to be found in the T-zone of lymph nodes. They have a dendritic morphology, show low levels of lysosomal enzymes and play a key role in antigen presentation. They ar S-100+/CD1a-/CD21-/CD35-/CD86+

Epidemiology

Extremely rare

Clinical features

Solitary lymph node disease is most common, but may present extranodally in skin1, intestines, soft tissue, liver or spleen.

Histopathology

Lymph nodes show a paracortical infiltrate with residual follicles. The neoplastic infiltrate is composed of spindle cells in a storiform pattern. There are usually admixed T-lymphocytes1. There is a close resemblance to follicular dendritic cell sarcoma/tumour.

Immunohistochemistry; see the immunohistochemical differentiation of histiocytic and dendritic cell neoplasms

Should be strongly positive	S-100	consistently positive0, 5/51
vimentin		consistently positive0
Should be negative	CD1a	negative0, 0/51
CD68		variably weakly positive0, 2/51
CD45		variably weakly positive0, 2/41
lysozyme		variably weakly positive0, 1/51
myeloid markers	myeloperoxidase	negative0, 0/41
myeloid markers	CD34	negative0, 0/21
FDC markers: should be negative	CD21	negative0, 0/51
	CD35	negative0, 0/51
	CNA.42	0/51
T-cell lineage markers; should be negative0	CD3	0/51
B-cell lineage markers; should be negative0	CD20	0/51
B-cell lineage markers; should be negative0	CD79a	0/21
CD30		negative0, 0/51
EMA		negative0, 0/21
cytokeratin		negative0

Ultrastructure

The tumour cells show complex intedigitating processes. Desmosomes and Birbeck granules are absent.

Differential diagnosis

Other histiocytic and dendritic cell neoplasms; see the immunohistochemical differentiation of histiocytic and dendritic cell neoplasms in particular follicular dendritic cell sarcoma/tumour. Interdigitating dendritic cell tumour is typically paracortical, while follicular dendritic cell tumour is diffuse or focally follicular in distribution.
malignant melanoma; also S-100 positive
fibroblastic reticular cell tumour1: shows a paracortical location but is negative for S-100, positive for SMA and desmin1.

Prognosis

Variable.

References

0World Health Organization Classification of Tumours, Tumours of the haematopoietic and lymphoid tissues, IARC Press 2001.

1Pileri, S.A., Grogan, T.M., Harris, N.L., Banks, P., Campo, E., Chan, J.K., Favera, R.D., Delsol, G., De Wolf-Peeters, C., Falini, B., Gascoyne, R.D., Gaulard, P., Gatter, K.C., Isaacson, P.G., Jaffe, E.S., Kluin, P., Knowles, D.M., Mason, D.Y., Mori, S., Muller-Hermelink, H.K., Piris, M.A., Ralfkiaer, E., Stein, H., Su, I.J., Warnke, R.A. and Weiss, L.M. Tumours of histiocytes and accessory dendritic cells: an immunohistochemical approach to classification from the International Lymphoma Study Group based on 61 cases. Histopathology 2002;41:1-29.

This page last revised 24.12.2002.