Histiocytic and dendritic cell neoplasms

True histiocytic and accessory dendritic cell tumours are very rare, constituting less than 1% of tumours presenting in lymph nodes. Many tumours previously thought to be of histiocytic or reticulum cells origin have been re-assigned¹:

Original terminology	Current terminology
Histiocytic lymphoma, nodular and diffuse	DLBCL, follicular lymphoma, grade 3, peripheral T-cell lymphoma
Histiocytic medullary reticulosis / malignant histiocytosis	Haemophagocytic syndrome
Malignant histiocytosis	ALCL
Regressing atypical histiocytosis	Primary cutaneous ALCL
Malignant histiocytosis of the intestine	Enteropathy type T-cell lymphoma
Histiocytic cytophagic panniculitis	Subcutaneous panniculitis-like T-cell lymphoma with haemophagocytic syndrome

Immunohistochemistry

The following five antibodies appear to be able to reliably distinguish between the histiocytic and accessory dendritic cell neoplasms in most cases, with additional morphological and ultrastructural features resolving the cases which depart from the usual immunophenotype².

	CD68	lysozyme	CD1a	S-100	CD21 or CD35
histiocytic sarcoma	positive	positive	negative	variable	negative
Langerhans cell tumours	positive	variable	positive	positive	negative
Interdigitating dendritic cell tumour	variable	variable	negative	positive	negative
follicular dendritic cell tumour	variable	negative	negative	negative	positive

For further details, see specific tumours. Immunoglobulin T cell antigen-receptor genes should be of germline configuration.

There is a case report of a tumour showing hybrid features (S100+/CD45+/CD68+/vimentin+/CD21-/CD35-, ultrastrucutral desmosome-like junctions) of follicular dendritic cell tumour and Interdigitating dendritic cell tumour³.

Prognosis

Usually aggressive neoplasms with a poor prognoses.

References

¹World Health Organization Classification of Tumours, Tumours of the haematopoietic and lymphoid tissues, IARC Press 2001.

²Pileri, 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.

³Dillon, K.M., Hill, C.M., Cameron, C.H., Attanoos, R.L. and McCluggage, W.G. Mediastinal mixed dendritic cell sarcoma with hybrid features. J Clin Pathol 2002;55:791-4.

This page last revised 13.5.2003.

©SMUHT/PW Bishop