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Platelet satellitism surrounding polymorphonuclear neutrophils has been observed almost exclusively in EDTA-treated blood at room temperature. The mechanism underlying this phenomenon is not understood fully. We report a case of platelet rosetting around atypical lymphocytes in peripheral blood smears made from EDTA-treated and untreated blood. Flow cytometry of the peripheral blood sample and immunohistochemical stains of the subsequent bone marrow biopsy specimen revealed a monoclonal B-cell population positive for CD5, CD20, and cyclin D1 and negative for CD3 and CD23; cytogenetic findings revealed a complex karyotype that included t(11;14). These findings were consistent with mantle cell lymphoma. To our knowledge, the finding of platelet satellitism involving mantle cell lymphoma cells in peripheral blood has not been reported previously.

Cutaneous plasmacytosis is a rare disorder that typically affects middle-aged to older individuals of Asian, particularly Japanese, descent. Clinically, it is characterized by multiple asymptomatic red-brown plaques and nodules on the trunk. Lymphadenopathy and hypergammaglobulinemia may be present. Histologically, the lesions show a moderately dense superficial and deep perivascular infiltrate composed predominantly of mature plasma cells without atypia or light chain restriction. We report our experience with five additional cases, including results of immunohistochemical studies for human herpes virus 8.