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Two elderly women with complex medical histories presented with erythematous patches, in one case involving the face and forearms, and in the other both elbows. Punch biopsies from both patients revealed intravascular proliferations of medium-sized and large cells with luminal occlusion typical of angioendotheliomatosis. Immunostaining did not show either lymphocytic or endothelial cell antigens but was consistent with a histiocytic differentiation of the intravascular cells in both cases, and was further substantiated by ultrastructural examination in one case. One patient received a course of cyclophosphamide therapy over 15 days. Skin lesions faded but did not disappear. The patient died 10 months later from cardiac and renal failure, which was most probably unrelated to the skin lesions. In the other case, lesions diminished but did not entirely resolve with treatment with low doses of oral prednisone. Angioendotheliomatosis can be divided into a malignant variant, which is an angiotropic lymphoma mostly of B-cell phenotype, and a benign, reactive variant, which is characterized by a proliferation of cells expressing endothelial cell markers. Only one case of angioendotheliomatosis with cells of histiocytic differentiation has been published previously under the name of intravascular histiocytosis. Our cases are very similar to the latter. The question arises as to whether intravascular histiocytic cell proliferation is a neoplastic proliferation of histiocytes or an early stage of classic reactive angioendotheliomatosis representing the residual cells associated with organization of microthrombi, which will be later followed by endothelial cell proliferation.

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The clinical and histological features of 16 patients with a primary cutaneous immunocytoma and 10 patients with a secondary cutaneous immunocytoma are reported. In all cases the diagnosis was based on the presence of monotypic plasma cells or lymphoplasmacytoid cells. Our data show that primary cutaneous immunocytomas are a distinct type of cutaneous lymphoma, characterized by (a) the presence of solitary or localized skin lesions (13 of 16 cases); (b) preferential localization on arms and legs (15 of 16 cases); (c) excellent response to local treatment (15 of 16 cases) and (d) a favourable prognosis. Histologically, these primary cutaneous immunocytomas are characterized by the presence of nodular or diffuse infiltrates with monotypic lymphoplasmacytoid/plasma cells located at the periphery of the infiltrates. Important clinical and histological differences were noted between primary and secondary immunocytomas. In the latter group more widespread skin disease was seen, often in the presence of paraproteins and/or autoimmune diseases. In contrast with the peripheral localization of the monotypic cells in primary cutaneous immunocytomas the monotypic lymphoplasmacytoid/plasma cells in secondary immunocytomas formed diffuse infiltrates or these cells were found dispersed throughout the infiltrate. There were no differences in clinical presentation or course between the different subtypes of cutaneous immunocytomas (lymphoplasmacytic, lymphoplasmacytoid and polymorphic immunocytomas). The differential diagnosis between primary cutaneous immunocytomas and cutaneous plasmacytomas, primary follicular centre cell lymphomas and cutaneous 'pseudolymphomas' is discussed.