Clinical, morphological and immunohistochemical characterization of a recurrent B1 type thymoma

Type B1 thymoma is widely accepted as a tumor with a non-aggressive behavior even in advanced stage. Most of these tumors are classified as Masaoka stage I or II. They rarely relapse or metastasize and the surgical treatment is considered curative. We have investigated a case of thymoma type B1, which relapsed 13 months after the primary tumor was excised. The patient was diagnosed with a local tumor recurrence after investigations due to the worsening of clinical symptoms of myasthenia gravis (MG). The therapy management of such cases is debatable and protocols not yet approved. For this reason, we have analyzed different clinical, morphological and immunohistochemical characteristics that may be considered as prognostic factors for a more aggressive behavior of such tumors. We have identified some morphologic characteristics rarely seen in this type of thymoma but none considered of prognostic value. In addition, we investigated some possible immunohistochemical markers that are generally associated with a more aggressive clinical outcome in different malignant tumors and thymic epithelial tumors. Among these markers, only p53 was positive and may be useful to predict a more aggressive evolution. In summary, probably the more appropriate approach of the patient is the clinical follow-up together with treatment of the clinical symptoms of myasthenia gravis.

Prostate lesions with cribriform / pseudocribriform pattern

Prostate lesions with cribriform / pseudocribriform architecture range from normal histological structures to infiltrative carcinoma. In each group of lesions with cribriform architecture (benign, premalignant and malignant intraductal or infiltrating), there are situations in which histological classification of the lesion is difficult or impossible on routine stains. A more wide-scale application of the immunohistochemical investigation for clearing up the problematic prostate lesions led to the definition and reclassification of cribriform lesions in distinct categories and sometimes very different in terms of progression, prognosis and treatment. This paper proposes an overview of the prostate lesions with cribriform / pseudocribriform architecture, emphasizing the morpho-immunohistochemical criteria for positive and differential diagnosis.

A nodular hyperplasia of the thymic epithelium (so-called microscopic thymoma)

We investigate a case of nodular hyperplasia of the thymic epithelium which was incidentally, microscopically discovered. Macroscopically there was no sign of tumor and the thymus was surgically removed for the therapy of the clinical symptoms of the myasthenia gravis worsened in two years of evolution. Histological in a general appearance of an involuted thymic tissue, a small nodular epithelial proliferation was identified. The epithelial proliferation was classified as A-type in the WHO histological classification of the thymic epithelial tumors. Generally, these microscopic thymomas range from 0.2 mm to 0.4 mm in size that corresponds to our finding that measured 0.25/0.35 mm. This lesion was singular; on additional sections examined, we did not find other areas. Even so, there is a tight connection between the myasthenia gravis, thymomas and these microscopic thymomas, the development of a thymoma from this lesion has not been proven.

Involution of the thymus: a possible diagnostic pitfall

There were investigated 22 cases from which the thymic tissue was removed either during surgery for cardiovascular malformations (n = 14), or for myasthenia gravis (n = 8). Histological sections were stained with routine morphologic methods, and immunohistochemistry was performed for cytokeratin, CD20, CD3, and S100 protein. Aspects characteristic for thymus involution were found in 11 cases without myasthenia gravis and in all cases with myasthenia gravis. Morphological changes of the thymus of involution are age-dependent. There were characterized stages of involution, with special reference to cortical - medulla inversion, lymphocyte depletion and sequestration. In advanced-stage of involution, epithelial cells are arranged in cords or compact islands, and could mimic a thymoma or a metastatic carcinoma. The immunohistochemical profile is similar but not identical to the active thymus. We noticed a decreased expression of cytokeratin, and a reduced number of CD3, CD20, and S100 positive cells. Morphologic and immunohistochemical peculiarities of the thymus of involution are discussed in relation with the specific pathology of the organ.

Direct spectroscopic detection of molecular dynamics and interactions of the calcium pump and phospholamban

In order to test molecular models of cardiac calcium transport regulation, we have used spectroscopy to probe the structures, dynamics, and interactions of the Ca pump (Ca-ATPase) and phospholamban (PLB) in cardiac sarcoplasmic reticulum (SR) and in reconstituted membranes. Electron paramagnetic resonance (EPR) and phosphorescence of probes bound to the Ca pump show that the activity of the pump is quite sensitive to its oligomeric interactions. In cardiac SR, PLB aggregates and inhibits the pump, and both effects are reversed by PLB phosphorylation. Previous analyses of PLB's oligomeric state were only in detergent solutions, so we used EPR and fluorescence to determine the oligomeric structure of PLB in its native state in lipid bilayers. Wild-type PLB is primarily oligomeric in the membrane, while the mutant L37A-PLB is monomeric. For both proteins, phosphorylation shifts the dynamic monomer-oligomer equilibrium toward oligomers, and induces a similar structural change, as indicated by tyrosine fluorescence; yet L37A-PLB is more effective than wild-type PLB in inhibiting and aggregating the pump. Fluorescence energy transfer shows that the Ca pump increases the fraction of monomeric PLB, indicating that the pump preferentially binds monomeric PLB. These results support a reciprocal aggregation model for Ca pump regulation, in which the Ca pump is aggregated and inhibited by association with PLB monomers, and phosphorylation of PLB reverses these effects while decreasing the concentration of PLB monomers. To investigate the structure of the PLB pentamer in more detail, we measured the reactivities of cysteine residues in the transmembrane domain of PLB, and recorded EPR spectra of spin labels attached to these sites. These results support an atomic structural model, based on molecular dynamics simulations and mutagenesis studies, in which the PLB pentamer is stabilized by a leucine-isoleucine zipper within the transmembrane domain.