Fusion of the NPM and ALK genes was detected in three of 18 patients with ALCL who had amplifiable DNA (17%, 95% confidence intervals 4% to 41%), but not in any patients with other NHL, HD, or lymphomatoid papulosis.
All other cases comprising T or null ALCL (17 cases), B ALCL (8 cases), Hodgkin's disease (HD) (15 cases), HD-like ALCL (23 cases), and lymphomatoid papulosis (9 cases), were negative forALK expression.
The aggregate results of these studies indicate that the t(2;5) translocation or other somatic mutations resulting in inappropriate expression of ALK are involved rarely if at all in the pathogenesis of Hodgkin's disease, but may be present in about 10% of cases of lymphomatoid papulosis and 20% of cases of CD30+ primary cutaneous large cell lymphoma.
Although initially found in primary nodal ALCL, recent studies suggest that NPM-ALK expression may occur in lymphoma at extranodal sites, including the skin; it remains controversial, however, whether CD30+ primary cutaneous lymphoma and its benign counterpart, lymphomatoid papulosis (LyP), express NPM-ALK in some cases.
CD30+ lymphoproliferative disorders (LD) represent a spectrum of entities ranging from self-limited proliferations or cutaneous lesions with favorable prognosis, such as lymphomatoid papulosis and primary cutaneous anaplastic large cell lymphoma (ALCL), to more aggressive malignancies such as systemic ALK-positive and ALK-negative ALCL.