primary plasma cell leukemia with hairy-cell morphology

Morphological heterogeneity, including various immature features, in atypical plasma cells sometimes makes the diagnosis of PCL difficult and may require an immunohistochemical or electromicroscopic examination to establish a definitive diagnosis.

Most of the leukemic cells in the peripheral blood can exhibit an unusual morphology similar to that of hairy-cell leukemia.

An unusual ‘hairy-cell’ variant of plasma cell myeloma has been described.

Kawano et al. reported a series of variously matured myeloma cases, containing proliferative VLA-5-negative and MPC-1-negative myeloma cells and IL-6-responsive immature cells, found predominantly in the peripheral blood.

Ontogenetically, B-cell tumors can be regarded as B-cells that arrested at a certain stage of differentiation when the neoplastic transformation occurred.

An analysis of the immunoglobulin variable region genes has provided invaluable information on the status of tumors in B-cell differentiation and has added an important dimension to the classification of B-cell tumors at a molecular level.

Germ-line repertoire

The germ-line repertoire of VL genes has been mapped and its involvement in B-cell tumors has been studied.

VL and VH genes obtained from leukemic cells in the peripheral blood of this case exhibit significant somatic hypermutation compared with that observed in germline genes.

In both VL and VH genes, extensive R mutations tended to cluster in the CDRs, whereas the R/S ratio in FRs were lower than expected.

These findings allowed us to speculate that the leukemic cells, with their unique hairy-cell-like morphology, were derived from B-cells that had been exposed to a hypermutation stage prior to their neoplastic transformation.

A sequence analysis of Vκ gene in κ light chain-expressing multiple myeloma shows that somatic hypermutation occurs in the course of the disease, clustering in the CDR regions.

Intraclonal diversities in the immunoglobulin genes are indicative of ongoing mutation (26) and allow the discrimination between germinal center B-cells, which show ongoing mutations, and post-germinal center B-cells, which do not (27).

References

 A case of primary plasma cell leukemia with hairy-cell morphology and lambda-type Bence-Jones protein. Immunohistochemical and molecular analysis. Tanioka F, Tamashima S, Shimizu S, Kobayashi H, Kobayashi Y, Sugimura H. Jpn J Clin Oncol. 2003 May;33(5):232-7. PMID: 12865467 (Free)

 Crogan TM, Spier CM. B-cell Immunoproliferative disorders, including multiple myeloma and amyloidosis. In: Knowles DM, editor. Neoplastic hematopathology, 2nd ed. Philadelphia: Lippincot Williams and Wilkins 2001;1564–5.

 Loo SY, Bhagavan NV, Scottolini AG. Double IgA bands in serum from a patient with lymphoplasmacytoid leukemia with hairy-cell morphology. Clin Chem 1987;33:2317–9.