Based on our series of 111 cases of non-Langerhans cell histiocytoses, we present a new unifying concept for this rare group of disorders. The common denominator is the monocyte/ macrophage, which presents with various histologic features probably due to the influence of cytokines. Non-Langerhans cell histiocytoses are classified according to the predominant mononuclear (vacuolated, spindle-shaped, xanthomatized, scalloped, and oncocytic) and/or multinucleate (Touton, ground-glass appearance, Langhans, and foreign body) histiocytic cell types. Variable mixtures of these cell types produce common polymorphous patterns with prominence of vacuolated, spindle-shaped, and xanthomatized histiocytes in juvenile xanthogranulomas and of scalloped and oncocytic histiocytes in adult xanthogranulomas. Rarely, unusual monomorphous reaction patterns are observed: mostly vacuolated histiocytes are seen in the mononuclear variant of xanthogranulomas, (early benign cephalic histiocytosis, and generalized eruptive histiocytoma. Xanthomatized histiocytes predominate papular xanthoma and rarely xanthoma disseminatum, whereas spindle-shaped histiocytes are evident in spindle cell xanthogranuloma and progressive nodular histiocytosis, scalloped histiocytes are evident in most cases of xanthoma disseminatum, and finally oncocytic histiocytes are evident in reticulohistiocytoma and multicentric histiocytosis. Immunohistochemical, ultrastructural, and clinical findings can rationally be adjusted to this unifying concept of non-Langerhans cell histiocytoses. The time course of lesions, the age of the patients, and the presence or absence of underlying internal diseases are, or may, at least partially, be related to and thus explain variations on the theme of the non-Langerhans cell histiocytic reaction.

The skin is the second most frequently affected organ system in lupus erythematosus. Although only very rarely life threatening--an example is lupus erythematosus-associated toxic epidermal necrolysis--skin disease contributes disproportionally to disease burden in terms of personal and psychosocial wellbeing, vocational disability, and hence in medical and social costs. Since several manifestations are closely associated with the presence and activity of systemic lupus erythematosus, prompt and accurate diagnosis of cutaneous lupus erythematosus is essential. This review aims to cover common, rare, and atypical manifestations of lupus erythematosus-associated skin disease with a detailed discussion of histopathological correlates. Cutaneous lupus erythematosus covers a wide morphological spectrum well beyond acute, subacute and chronic cutaneous lupus erythematosus, which are commonly classified as lupus-specific skin disease. Other uncommon or less well-known manifestations include lupus erythematosus tumidus, lupus profundus, chilblain lupus, mucosal lupus erythematosus, and bullous lupus erythematosus. Vascular manifestations include leukocytoclastic and urticarial vasculitis, livedoid vasculopathy and livedo reticularis/ racemosa. Finally, we discuss rare presentations such as lupus erythematosus-related erythema exsudativum multiforme (Rowell syndrome), Kikuchi-Fujimoto disease, extravascular necrotizing palisaded granulomatous dermatitis (Winkelmann granuloma), and neutrophilic urticarial dermatosis.