Persistent agmination of lymphomatoid papulosis: an ongoing debate.

Background: Persistent agmination of lymphomatoid papulosis (PALP) has been a matter of controversy in the literature, some authors suggesting that it represents composite lymphoma, others localized lymphomatoid papulosis (LyP). Patient and Methods: A 64-year-old man was referred to our outpatient center complaining of papular eruptions lasting 3 years. At physical examination, he showed papulonodular lesions on the trunk and extremities. Some patches on the trunk and upper arms were also observed. Both types of lesion were biopsied and studied on histological, immunohistochemical and molecular grounds. Results: The nodular lesion revealed the classical features of LyP type A, while the patch was characterized by the presence of a superficial and deep infiltrate with perivascular and interstitial location, consisting of mature lymphocytes admixed with plasma cells and large atypical cells that became more numerous beneath the epidermis. On immunohistochemistry the two lesions presented the same profile. Conclusion: Our case suggests that PALP does not correspond to localized LyP, as it can involve different skin areas since its presentation. Furthermore it rules out the possibility that PALP is a composite lymphoma. In fact, the same cytological and phenotypic characteristics were detected in all samples, including those taken from patchy areas.