Pyogenic lymphoma of the skin: a peculiar variant of primary cutaneous neutrophil-rich CD30+ anaplastic large-cell lymphoma. Clinicopathological study of four cases and review of the literature.

Systemic anaplastic large-cell lymphoma (ALCL) in human immunodeficiency virus (HIV)-infected individuals showing an extensive infiltrate of neutrophils has been reported and referred to as 'neutrophil-rich' CD30+ ALCL. Secondary cutaneous involvement has been found in a subset of these cases. We report the clinicopathological features of four immunocompetent patients with primary cutaneous neutrophil-rich ALCL and present a new histological subtype with a dissolute growth pattern of CD30+ tumour cells. Four HIV-negative patients presented with rapidly growing solitary or multiple tumours located on the face. Ulceration of the lesions with purulent discharge was a typical finding. Various inflammatory dermatoses were considered clinically in all cases. The histological hallmark was a large number of neutrophils in the infiltrate that masked neoplastic CD30+ anaplastic cells. In two cases, a dissolute growth pattern of anaplastic tumour cells was observed. In two cases, a strong correlation between tumour growth and interleukin (IL)-8 cytokine pattern as well as the production of IL-8 by tumour cells was demonstrated. The diagnosis of neutrophil-rich ALCL is challenging clinically and histologically as the tumour cell compartment is masked by an extensive inflammatory infiltrate of neutrophils and other reactive cells such as histiocytes which may be mainly due to release of IL-8 by tumour cells. The term 'pyogenic' designates the typical feature of this distinct neutrophil-rich ALCL, namely abscess formation ('pyo-') by cytokines (IL-8) produced by tumour cells ('-genic'). The clinical behaviour of this type is the same as in primary cutaneous CD30+ ALCL with classical histological presentation.