A patient with myelodysplastic syndrome (refractory anemia with excess of blasts in transformation, RAEB-T) presented with generalized granulocytic sarcomas involving the skin. The diagnosis was confirmed by skin and bone marrow biopsies. Partial myeloperoxidase deficiency was noted in the circulating polymorphonuclear leukocytes and the more differentiated tumor cells in the granulocytic sarcoma. This observation suggests that such leukocytes may be derived from the abnormal ‘leukemic’ clone.

This is a description of a novel combination of chromogenic multiplex immunohistochemistry, digital pathology, computer-aided cell detection and topographical analysis of tumor tissue to allow a detailed study of the immune infiltrate. This is applied to a rare clinical case, where a tumor sample is available from an infant with metastatic neuroblastoma at the point of spontaneous regression. This allowed detailed analysis of the immune infiltrate, including spatial distribution and phenotype of lymphoid and myeloid populations, with a distinction between heterogeneous areas within the intra- and extra- tumoral immune microenvironments. The mechanism of spontaneous regression in congenital neuroblastoma is poorly understood, but the data obtained suggested an immune-mediated phenomenon, characterised by an adaptive T cell driven response with a significant delayed-type hypersensitivity (granulomatous) component.