We assessed the usefulness of several immunohistochemical stains in distinguishing these two neoplasms, including cytokeratin 7, cytokeratin 20 (CK20), neuron-specific enolase, chromogranin, synaptophysin, neurofilaments (NF), thyroid-transcription factor-1 (TTF-1), CD56 antigen, S-100 protein, vimentin, c-erbB-2 oncoprotein, and CD117 antigen. All 13 cases of Merkel cell carcinoma evaluated were positive for CK20, and negative for TTF-1. Twelve of 13 Merkel cell carcinoma cases were positive for NF. Eleven of 13 cases of small cell lung carcinoma were positive for TTF-1. All small cell lung carcinoma cases were negative for NF, and all but one were negative for CK20. In terms of the remaining antigens, there were no differences of significance between the two neoplasms. These findings suggest that a set of three immunohistochemical stains, including CK20, NF, and TTF-1, is useful in affording a distinction between Merkel cell carcinoma and small cell lung carcinoma.

Mantle cell lymphoma (MCL) is characterized by the chromosomal translocation t(11;14), which involves rearrangement of the bcl-1 proto-oncogene to the immunoglobulin heavy chain gene and results in overexpression of cyclin D1 mRNA. In this study, we evaluated the diagnostic relevance of three methods that may be helpful in the diagnosis of MCL: in situ hybridization (ISH) and a stringent reverse transcriptase-polymerase chain reaction (RT-PCR) protocol for cyclin D1 mRNA, and immunohistochemistry for cyclin D1 protein. The study group included 37 paraffin-embedded specimens (25 from lymph nodes and 12 from extranodal tissues) from 30 patients. MCL diagnosis was performed according to the Revised European-American Classification of Lymphoid Neoplasms. Twenty-nine patients with non-MCL lymphoproliferative disorders comprised the control group. Biotin-labeled ISH was performed in 28 cases of MCL, 24 (86%) of which were found to be positive. As shown by ISH in extranodal tissues, cyclin D1 mRNA was present not only in neoplastic lymphoid cells, but in other cell types as well. For this reason, RT-PCR results were considered reliable for MCL diagnosis only on informative material (from tissues that do not normally express cyclin D1); this method was evaluated as positive in 16 of 18 (89%) MCL cases. Cyclin D1 immunopositivity was present in 20 of 29 (69%) MCL cases. No members of the control group were found to express cyclin D1 mRNA by either ISH or RT-PCR under the stringent conditions used. In conclusion, stringent RT-PCR for cyclin D1 expression can be helpful in MCL diagnosis in paraffin-embedded material from lymph nodes. ISH is a sensitive method for cyclin D1 mRNA detection; its sensitivity is superior to that of cyclin D1 immunohistochemistry and similar to that of the stringent RT-PCR used. ISH is very specific as well, clearly more specific than RT-PCR, because it allows the correlation of molecular findings with morphology. This method can be applied on all types of paraffin-embedded tissues and provides an accurate tool for MCL diagnosis.

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This study shows that hTERT re-expression takes place both in hepatic regeneration occurring in cirrhosis and in the early steps of hepatocarcinogenesis, and involves mainly the beta-splice variant of this molecule. Additional regulatory mechanisms may be required for the expression of the full-length hTERT transcript.

The expression and the distribution of the c-myc oncogene product (p62) was studied by a 3-step immunoperoxidase technique using the monoclonal antibody myc 1-6 E10 in 22 cases of normal endometrium (11 proliferative and 11 secretory phase), 43 endometrial hyperplasias (24 adenomatous and 19 adenocystic) and 26 endometrial carcinomas. Increased expression of c-myc product appeared in endometrial carcinomas compared with respective non-neoplastic tissue (p < 0.001). The immunolocalization of the c-myc protein shows a consistent difference between the various histologic patterns of non-neoplastic and neoplastic endometrium. Nuclear staining of the c-myc product was demonstrated in epithelial cells of the proliferative phase and predominantly in poorly differentiated forms of endometrial carcinomas. On the other hand cytoplasmic staining was found predominantly in the secretory phase and in well differentiated carcinomatous endometrium. In hyperplastic endometrium an intermediate immunohistochemical pattern was observed. The results of the present study emphasize that c-myc product overexpression and localization plays an important role in initiation, differentiation and progression of endometrial carcinomas.