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A New WHO-EORTC System for Classifying Primary Cutaneous B-Cell Lymphomas

Reclassification using a new system yielded some changes in diagnosis.

The diagnosis and classification of lymphomas are fraught with difficulties. The existence of multiple classification systems (e.g., REAL, WHO, and EORTC) adds to the complexity. A new, combined WHO-EORTC system classifies primary cutaneous B-cell lymphomas as one of three major types: primary cutaneous marginal zone B-cell lymphomas (PCMZL); primary cutaneous follicle center lymphomas (PCFCL); and primary cutaneous large B-cell lymphomas, leg type (PCLBCL-LT).

Researchers retrospectively analyzed 300 patients in the Dutch Cutaneous Lymphoma Group registry whose disease had been diagnosed using EORTC criteria. They reclassified each patient, using immunohistochemical stains when possible, calculating rates of 5-year overall and disease-specific survival, and evaluating prognostic markers.

The WHO, EORTC, and combined systems each identified 71 cases of PCMZL. Only six patients in this class (8.5%) developed extracutaneous disease. The overall and disease-specific survival rates were 94% and 98%, respectively.

Under the new system, 171 lymphomas were classified as PCFCL (including 9 classified as PCLBCL-LT under EORTC and 109 as diffuse large B-cell lymphoma under WHO). The trunk and head were affected in most patients, with diffuse distribution in 64%, follicular-diffuse distribution in 34%, and follicular distribution in 2%. Bcl-6 was expressed by more than 90% of PCFCLs, with Bcl-2, MUM-1, FOXP1, or CD10 expressed in a few. The overall and disease-specific survival rates were 87% and 95%, respectively. In multivariable analysis, only location on the leg and FOXP1 expression had significant negative prognostic effects on overall survival. Patients with PCFCL of the leg developed extracutaneous disease six times more frequently than patients with disease at other sites; the overall and disease-specific survival rates for leg PCFCL were 22% and 41%, respectively.

The new system identified 58 PCLBCL-LTs (including 7 classified as PCFCL under EORTC). Most of these lymphomas expressed Bcl-2, MUM-1, FOXP1, or Bcl-6; 46% of patients in this class developed extracutaneous disease and died from the lymphoma. Overall and disease-specific survival rates were 37% and 50%, respectively. Multivariable analysis identified no independent prognostic markers. Survival was unaffected by disease location.

Comment: The clinicopathologic entities of primary cutaneous B-cell lymphoma appear to be well defined, with distinctive immunologic and molecular features. PCMZL and PCFCL are indolent types with excellent prognoses and should be treated nonaggressively, but PCLBCL-LT is aggressive and requires chemotherapy.

The new WHO-EORTC classification system reliably distinguished PCMZL and PCFCL (follicular and follicular-diffuse patterns). However, more than half of the lymphomas formerly classified as diffuse large B-cell type under other schemes were reclassified as PCFCL in the new system (with an implied need for a change from chemotherapy to radiotherapy). PCFCL of the leg indicated a worse prognosis than PCFCL elsewhere. In PCLBCL-LT, age and extent of the lymphoma, not location, were relevant markers. The usefulness of immunologic studies for prognosis is still unclear, although they provide a clear benefit for diagnosis and for delineating the distinct features of lymphoma subtypes.

— Angelica Selim, MD

Published in Journal Watch Dermatology May 4, 2007

Citation(s):

Senff NJ et al. Reclassification of 300 primary cutaneous B-cell lymphomas according to the new WHO-EORTC classification for cutaneous lymphomas: Comparison with previous classifications and identification of prognostic markers. J Clin Oncol 2007 Apr 20; 25:1581-7.

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