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A letter to the editor is presented in response to the article on patient with myeloid sarcomas (MS).

Franco V, Florena A M, Ascani S, Paulli M, Salvato M & Pileri S A (2004) Histopathology 44, 381–386 CD27 distinguishes two phases in bone marrow infiltration of splenic marginal zone lymphoma To investigate CD27 expression in splenic marginal zone lymphoma (SMZL), an indolent low-grade B-cell lymphoma with constant involvement of the bone marrow, especially with an intrasinusoidal pattern. It is not clear if the neoplastic clone is composed of virgin or somatically mutated B cells. CD27 is reported to be a hallmark of memory B cells. We evaluated 64 bone marrow biopsy specimens (BMBs) from 36 patients with SMZL for the expression of CD27. For comparison, splenectomy specimens of patients with traumatic splenic rupture or with SMZL were used. All BMBs showed lymphomatous infiltration. When located in the marrow sinusoids, neoplastic cells were CD27– in all cases and therefore corresponded to naive B cells. In nodular/interstitial infiltration, the cells were CD27+ and therefore corresponded to memory B cells. No difference in immunohistochemical expression of B and T antibodies was found between intrasinusoidal and interstitial/nodular infiltration. CD27 was constantly expressed in the splenic marginal zone of normal spleen, surgically removed for trauma, and in seven out of 10 spleens with SMZL. We propose the existence of two different phases of neoplastic progression with, first, expansion of a virgin B clone in the bone marrow and, following exposure to antigen, a re-colonization of the bone marrow. [ABSTRACT FROM AUTHOR]

Pileri S A, Cavazza A, Schiavina M, Zompatori M, Pederzoli M, Goldfischer M, Sabattini E, Ascani S, Pasquinelli G, Bonetti F & Colby T V (2004) Histopathology 44, 156–163 Clear-cell proliferation of the lung with lymphangioleiomyomatosis-like change : To describe two cases of a peculiar pulmonary lesion, which expand both the morphological and the immunophenotypic spectrum of perivascular epithelioid cell (PEC)-related disorders. : One man and one female, with and without the tuberous sclerosis complex (TSC), respectively, showed pulmonary cysts and small nodules on computed tomography scan. In the former, lymphangioleiomyomatosis (LAM) was suspected. In both cases, an open lung biopsy was performed, whose cut surface displayed numerous cysts lined by thin/thick septa. Microscopically, the septa were associated with micronodular or interstitial proliferation of medium/large-sized elements with abundant clear (periodic acid–Schiff-positive/diastase-sensitive) cytoplasm and distinct cell borders, embedded in fibrous tissue. The elements were CD34+, vimentin-positive and, to a lesser extent, HMB-45+ and MART-1+. The stains for specific muscle actin, desmin, S100 protein, CD31, FVIIIRAg, cytokeratins, CD45, CD68, oestrogen and progesterone receptors were all negative. Ki67 labelling was <1%. Electron microscopy displayed cytoplasmic vacuoles containing glycogen particles. The TSC1 and TSC2 gene status could not be assessed because of poor DNA preservation. In the man with TSC, a focus of micronodular pneumocyte hyperplasia was also found. : Because of the coexpression of CD34 and melanoma-associated antigens and the occurrence of TSC in one patient, the cases described here add a new piece to the puzzle of PEC lesions and contribute to the open discussion on the origin of LAM and LAM-like proliferations. [ABSTRACT FROM AUTHOR]

Diffuse large B-cell lymphoma (DLBCL) is the commonest type of lymphoid tumour world-wide. This category was included both in the REAL and WHO Classification aiming to lump together all malignant lymphomas characterized by the large size of the neoplastic cells, B-cell derivation, aggressive clinical presentation, and the need for highly effective chemotherapy regimens. These tumours are detected as primary or secondary forms both at the nodal and extranodal levels, in immunocompetent hosts as well as in patients with different types of immunosuppression. They display a significant variability in terms of cell morphology and clinical findings, which justifies the identification of variants and subtypes. Among the latter, the primary mediastinal one does actually correspond to a distinct clinicopathological entity. Immunophenotypic, tissue microarray and molecular studies underline the extreme heterogeneity of DLBCLs and suggest a subclassification of the tumour, based on the identification of different pathogenic pathways, which might have much greater relevance than pure morphology for precise prognostic previsions and adoption of ad hoc therapies. The more recent acquisitions on the pathobiology of DLBCLs are reviewed in the light of the authors' experience, aiming to contribute to the existing debate on the topic. [ABSTRACT FROM AUTHOR]