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The revolutionary evolution in science and technology over the last few decades has made it possible to face more adequately three main challenges of modern medicine: changes in old diseases, the appearance of new diseases, and diseases that are unknown (mostly genetic), despite research efforts. In this paper we review the road travelled by pathologists in search of a method based upon the use of routine instruments and techniques which once were available for research only. The application to tissue studies of techniques from immunology, molecular biology, and genetics has allowed dynamic interpretations of biological phenomena with special regard to gene regulation and expression. That implies stepwise investigations, including light microscopy, immunohistochemistry, in situ hybridization, electron microscopy, molecular histopathology, protein crystallography, and gene sequencing, in order to progress from suggestive features detectable in routinely stained preparations to more characteristic, specific, and finally, pathognomonic features. Hematoxylin and Eosin (H&E)-stained preparations and appropriate immunohistochemical stains have enabled the recognition of phenotypic changes which may reflect genotypic alterations. That has been the case with hepatocytic inclusions detected in H&E-stained preparations, which appeared to correspond to secretory proteins that, due to genetic mutations, were retained within the rough endoplasmic reticulum (RER) and were deficient in plasma. The identification of this phenomenon affecting the molecules alpha-1-antitrypsin and fibrinogen has led to the discovery of a new field of cell organelle pathology, endoplasmic reticulum storage disease(s) (ERSD). Over fifty years, pathologists have wandered through a dark forest of complicated molecules with strange conformations, and by detailed observations in simple histopathological sections, accompanied by a growing background of molecular techniques and revelations, have been able to recognize and identify arrays of grotesque polypeptide arrangements.

Aims: Cytokeratin (CK) 7 and CK19 expression, present in hepatic progenitor cells (HPCs) and in cholangiocytes but not in normal hepatocytes, has been reported in some hepatocellular carcinomas (HCCs); however, the incidence and relevance of this expression in HCC in Caucasians is not known. Therefore, our aim was to study the occurrence and clinicopathological characteristics of HCC expressing CK7 and/or CK19 in 109 Caucasian patients. Methods and results: The expression of hepatocellular differentiation markers (Hepar, canalicular polyclonal carcinoembryonic antigen), biliary/progenitor cell markers (CK7, CK19), α-fetoprotein (AFP), p53 and β-catenin in HCC was semiquantitatively assessed by immunohistochemistry. Of 109 HCCs, 78 were CK7–/CK19– (72%), 13 CK7+/CK19– (12%), seven CK7–/CK19+ (6%), 11 CK7+/CK19+ (10%). CK19 expression was significantly associated with elevated serum AFP (400 ng/ml) ( P = 0.023), tumour AFP expression ( P < 0.0001), presence in serum of anti-hepatitis B core ( P = 0.016), less fibrosis in non-neoplastic parenchyma ( P = 0.009) and less nuclear β-catenin expression ( P = 0.021). CK7 expression was significantly associated with elevated serum bilirubin (> 2 mg/dl) ( P = 0.0005) and less nuclear β-catenin expression ( P = 0.003). HCC expressing CK19 had a higher rate of recurrence ( P = 0.009, hazard ratio 12.5, n = 31) after liver transplantation compared with CK19– tumours. Conclusions: In our series, 28% of HCCs contained cells expressing CK7 and/or CK19. They potentially derive from HPCs. The higher recurrence rate of CK19+ HCC after transplantation suggests a worse prognosis for these HCCs compared with CK19– HCC. [ABSTRACT FROM AUTHOR]

The dendritic cells in skin biopsies from 36 fetuses (from 16 weeks' gestational age on) and neonatal infants of different ages were investigated using a number of markers for various cells of the immune system and immunohistochemistry. Epidermal Langerhans' cells were found in all cases in a predominantly basal localization. The number of OKT6-positive Langerhans' cells and the development of their dendritic processes gradually increased with age. Dermal dendritic cells were present as well. Both HLA-DR-positive and Leu-10-positive dermal dendritic cells were found in the superficial and deep dermis, often in a perivascular distribution. The OKT6-positive dermal dendritic cells were few in number and occurred only in the upper dermis.

By use of the indirect immunoperoxidase method, lysozyme was localized in the serous glands and serous parts of mixed mucous-serous glands of the nasal respiratory area. Histochemically, lysozyme was absent from acini containing acid mucosubstances. These findings are in agreement with localizations of lysozyme in glands at other sites. [ABSTRACT FROM AUTHOR]

ABSTRACT- Ten liver biopsy specimens from nine patients with PBC stages II to IV were studied immunohistochemically with a broad panel of monoclonal antibodies. In areas of bile-duct proliferation, many BA1+ B-lymphocytes and OKT4+/Leu3a+ helper/inducer T-cells were observed, admixed with some C3b-receptor positive, mono-and polymorphonuclear OKM1+ cells. Numerous IgM-containing plasma cells were seen in portal tracts showing bile-duct proliferation. In contrast, areas of piecemeal necrosis and intralobular spotty necrosis consisted mainly of OKT4+/Leu3a+ helper/inducer, and OKT8+ suppressor/cytotoxic T-cells, admixed with some OKM1+ polymorphonuclear granulocytes. Almost no BA1+ B-lymphocytes or Ig-containing plasma cells were observed in areas of piecemeal necrosis and spotty necrosis. Major histocompatibility complex (MHC)-class I antigens (i.e. HLA-A,B,C) were demonstrated either on the liver cell membrane, or on sinusoidal lining cells. The latter also expressed MHC-class II antigens (i.e. HLA-DR). In two liver biopsies, an increased expression of HLA antigens was observed near areas of piecemeal and spotty necrosis. Our results indicate that several immune mechanisms each with a particular topographical distribution, are operative in PBC. Inflammatory cells, involved in humoral immunity, are present mainly in areas of bile duct proliferation. In contrast, the effector cells of antigen-specific cellular cytotoxicity are present in areas of piecemeal necrosis and spotty necrosis. In the latter areas, a pronounced expression of MHC products representing the afferent limb of the cell-mediated immune response, may permit an optimal T-cell-mediated immune effect or, eventually, result in adverse effects. [ABSTRACT FROM AUTHOR]

The enzyme and immunohistochemical features of lymphnodes showing sinus histiocytosis have been studied. Sinus histiocytes with phenotype OKM1 0KT4 Leu3a To5 OKIal showed strong acid phosphatase and non-specific esterase, weak endogenous peroxidase and no ATPase activities. In nine out of ten lymph nodes, paracortical collections of dendritic OKT6 OKIal cells were observed. In two of the four cases studied these dendritic cells showed strong ATPase activity. We suggest that the dendritic OKT6 OKIal ATPase interfollicular cells represent newly arrived veiled cells (VC) which have entered the lymph node by the afferent lymph, settled in the interfollicular area and are probably involved in the induction of a cellular immune response. OKT6 OKIal ATPase VC may subsequently transform into mature, OKT6 OKIal ATPase interdigitating reticulum cells which are involved in the negative feedback of the cellular immune response. The association with sinus histiocytosis is probably related to the fact that an increase in mononuclear phagocytes in the afferent lymph is accompanied by a relative increase in VC. Our results demonstrate that in lymph nodes showing sinus histiocytosis, two cell types increase in number, i.e. an Ia sinusoidal cell, engaged in phagocytosis of foreign material, and an Ia dendritic cell in the interfollicular area, probably involved in the induction of a cellular immune response. [ABSTRACT FROM AUTHOR]

We compared the paracortical area in 4 cases of dermato-pathic lymphadenitis (DL) with the same area in 11 cases of various other reactive conditions of the lymph node by immuno- and enzymehis-tochemical techniques. In addition, electron microscopy was performed on threee cases of DL. The paracortical nodules in DL proved to be composed of a variable number of dendritic, OKT6+ OKIa+ ATP-ase+ cells, admixed with helper T-lymphocytes. All other lymph nodes studied lacked dendritic OKT6+ cells, whereas OKIa positivity was found in the cortical (follicular centers and mantle zones) and paracortical area (lymphocytes and scattered dendritic cells). Short incubation for ATPase revealed a paracortical, pericellular staining pattern in cases of DL, whereas in all other cases this staining pattern was observed only after long incubation times. On electron microscopy, three types of dendritic cells were found in DL, namely interdigitating reticulum cells (IDRC), Langerhans cells (LC) and macrophages. Intermediate forms between IDRC and LC, containing a few Birbeck granules and a well developed rough endoplasmic reticulum, were found. It is suggested that immunoreactivity for the monoclonal antibody 0KT6 is restricted to cases of DL, and is due to the appearance of dendritic cells that have LC-characteristics. These cells either arrive from the skin along afferent lymph vessels, or are the result of a local transformation process of IDRC that acquire LC-characteristics, i.e. OKT6 immunoreactivity and Birbeck granules. [ABSTRACT FROM AUTHOR]

The expression of the selectin receptor LAM-1/Leu 8 was analysed in normal and in inflamed liver tissue and its expression on mononuclear inflammatory cells was correlated with their topographical distribution in various compartments of the inflamed liver, in order to obtain new insights on possible molecular mechanisms involved in the traffic of mononuclear inflammatory cells throughout the diseased hepatic parenchyma. In normal liver tissue, few scattered mononuclear cells in portal and lobular parenchyma corresponded lo both CD4+ and CD8+, as well as to CD45RA+ (2H4+) naive and CD45RO+ (UCHLI+) memory T cells, and were LAM-1/Leu 8+. In acute and chronic inflamed liver biopsies. CD45RO+ (UCHLI+)CD4+ and CD8+ memory T cells largely predominated in both portal and lobular parenchyma. The expression of LAM- 1/Leu 8 antigen on these memory T cells varied according to their localization in the liver parenchyma, and it was not correlated with specific aetiological causes. In acute hepatitis, the vast majority of T lymphocytes were LAM-1/Leu 8 . In chronic active hepatitis, memory T cells in portal tracts expressed LAM-1/Leu8, whereas virtually all intralobular T cells accumulating in areas of periporial and intralobular inflammation were LAM-1/Leu8+. In chronic persistent hepatitis, the LAM-1/Leu8+ T cells largely predominated among the numerous mononuclear inflammatory cells within enlarged portal tracts, whereas LAM-1/Leu 8 T cells were restricted to areas of intralobular "spotty" inflammation. Therefore, two phenotypical populations can be recognized among the memory T cells in inflamed liver tissue, according to their topographical localization: LAM-1/Leu8+ T cells predominating in portal tracts, and LAM-1/Leu 8- T cells predominating in the lobular parenchyma. These data show that during their migration through the inflamed liver parenchyma, memory T lymphocytes undergo phenotyical changes (LAM-1/Leu8 shedding) according to their localization indifferent liver compartments (portal tracts vs. lobular parenchyma), suggesting multiple cellular and molecular mechanisms involved in the regulation of the leucocyte traffic through inflamed liver tissue. [ABSTRACT FROM AUTHOR]

The present study reports a rare case of systemic M. serofulaceum infection in an AIDS patient and analyses the inflammatory infiltrate in a lymph node by immunohistochemistry. Special emphasis is put on the histiocytes. The diffuse infiltrate consists mainly of large histiocytes that contain numerous bacilli. These cells display the phenotype of mature histiocytes and in addition coexpress the antigens recognized by RFD7 and RFD9, both markers of different subsets of histiocytes which have been reported to be co-expressed by the infected histiocytes in the infiltrate of lepromatous lepra. Interdigitating reticulum cells are rare as well as T cells which are mainly of the suppressor/cytotoxic type. These findings are similar to those reported for lepromatous lepra and might indicate common deficiencies in T cell macrophage interactions in both conditions. Superimposed on the diffuse infiltrate of large histiocytes we observed 'monocytic granulomas', the presence of which might he related to a reactional state comparable to crythema nodosum leprosum, a reactional state of lepromatous lepra. [ABSTRACT FROM AUTHOR]

Using an indirect immunoperoxidase technique on frozen sections with the monoclonal antibody 96.5, we investigated the in situ distribution of melanotransferrin, a transferrin (Tf) and transferrin receptor (TfR) related glycoprotein, in human liver. Specimens included normal liver, liver in iron overload, hepatocellular carcinoma, angioma and foetal liver. On light microscopy, immunoreactivity was almost exclusively present on sinusoidal lining cells, apparently endothelial cells; the pattern was similar in normal and in iron-loaded liver. A gradient of more enhanced staining in acinar zone II and III was observed. The endothelial localization of the staining was supported by the positivity of the central vein endothelium and of the angiomas. Immunoelectron microscopy on three liver specimens showed positivity on sinusoidal endothelial cells but not on Ito and Kupffer cells. In addition, positivity on rough endoplasmic reticulum vesicles of some hepatocytes was also present. Four hepatocellular carcinomas showed an intense staining in tumour cells, 3 were weakly positive and 3 were negative. In the foetal livers, the central vein endothelium was positive from 21 weeks of gestation onward and additional positivity of zone III sinusoidal endothelial cells was present from 27 weeks on. The present results show that in the liver melanotransferrin has a localization different from Tf and the TfR. These latter molecules are predominantly localized in parenchymal cells. In addition, there does not appear to be a coordinate regulation secondary to iron storage, between melanotransferrin, Tf and the TfR. The observed gradient in the staining pattern in foetal and adult liver specimens further supports the heterogeneity of the endothelial cell population in the liver and suggests a developmental relationship between endothelial cells of sinusoids and central vein. [ABSTRACT FROM AUTHOR]

ABSTRACT- The portal and acinar zone 1 (periportal) inflammatory infiltrate in acute hepatitis A (HA) strongly resembles piecemeal necrosis (PMN) in chronic hepatitis B (HB). The latter infiltrate has been characterized in detail previously, and a predominance of suppressor/cytotoxic T cells has been demonstrated. For comparison we analyzed the infiltrate in acute HA in three liver biopsies, applying a broad panel of monospecific and monoclonal antibodies. In two cases, helper/inducer T cells surrounded by B lymphoid cells represented the main lymphoid subset in all portal areas. In the third liver biopsy, a case of acute HA superimposed on a pre-existing chronic HB, the cellular composition of the inflammatory infiltrate varied from one portal tract to another. Despite the morphological resemblance between the inflammatory infiltrate in acute HA and PMN in chronic HB, a clear-cut difference in the composition of both infiltrates is obvious from our results. By virtue of the presence of numerous suppressor/cytotoxic T cells, PMN in chronic HB represents the morphological expression of a cellular immune response, whereas the predominance of helper/inducer T cells, admixed with B cells and plasma cells in acute HA represents the morphological expression of a humoral immune response. [ABSTRACT FROM AUTHOR]

Describes a case of a male newborn with a mixed hepatoblastoma that contained different types of structure mimicking stages of normal and aberrant intrahepatic bile duct development. Examination of a needle liver biopsy; Necrotic foci of embryonal-type cells; Mesenchymal component of the tumor; Immunohistochemistry.