[Cutaneous B cell lymphoma in chronic Borrelia burgdorferi infection. Report of 2 cases and a review of the literature].

Low-grade malignant B-cell lymphomas of the skin can be distinguished from lymphadenosis benigna cutis (Bäfverstedt) by immunohistological methods developed in the last few years. Its coexistence with Borrelia burgdorferi infection can be shown by clinical and serological findings. In the chronic stage of this infection, lymphocytic cell infiltrations consistent with histological and immunohistological findings of malignant B-cell lymphoma can be found. Predominantly at the extremities, multiple plaque-shaped or nodular lesions are seen, showing a follicular pattern in their periphery. The tumors do not respond to antibiotic therapy. They regress totally after X-ray treatment, but local recurrences are rather common. They show a long persistent course with only slow progression and seem to be of low-grade malignancy independent from the cytological findings. In most cases the tumors remain limited to the skin and to one anatomical site; nevertheless, the development of systemic involvement has been reported. We present two cases of malignant B-cell lymphoma of the skin in patients with chronic B. burgdorferi infection. Both cases showed the typical clinical and histological features of this entity. Similar reports from the literature indicate close relationships with the chronic stage of Borrelia infection, with the simultaneous presence of acrodermatitis chronica atrophicans as an indicator. We conclude that an elevated titer indicating Borrelia infection is an important finding for the diagnosis and prognosis of this particular type of cutaneous B-cell lymphoma.