Presence of human herpesvirus-8 DNA sequences and overexpression of human IL-6 and cyclin D1 in inflammatory myofibroblastic tumor (inflammatory pseudotumor).

Inflammatory myofibroblastic tumor (IMT) is composed of myofibroblasts, plasma cells, and lymphocytes. Cytokines are possibly involved in its pathogenesis. Human herpesvirus-8 (HHV-8) encodes cell cycle regulatory and signaling proteins. A combination of nested PCR with several negative controls and Southern blot methods showed the presence of HHV-8 DNA in seven cases of IMT. Additionally, strong expression was demonstrated by in situ hybridization in many tumoral nuclei. Most of the myofibroblasts in all of the cases were immunoreactive for human IL-6 and cyclin D1. These cytokines probably have a paracrine action and may sustain myofibroblastic growth. HHV-8 could play an essential role in triggering IMT development by a local reactivation of viral lytic replication. The relationship between HHV-8 and immunosuppression status as the only associated cause for tumorigenesis should be revised.

Telomerase activity in pulmonary neuroendocrine tumors: correlation with histologic subtype (MS-0060).

The authors measured telomerase activity using the telomeric repeat amplification protocol-enzyme-linked immunosorbent assay method in 13 neuroendocrine pulmonary neoplasms and in non-neoplastic frozen lung samples from the same patients. These cases belonged to the complete neuroendocrine neoplastic spectrum: four typical carcinoids, three atypical carcinoids, four large cell neuroendocrine lung carcinomas, and two small cell lung carcinomas. The authors performed the same assay for 52 non-neoplastic lung tissues from the surgical files in their department (negative controls). They verified the presence (or absence) of neoplastic tissue in every case by looking at one frozen section done in the same tissue used for telomerase assay. The telomerase activity level in non-neoplastic tissues (mean, 182 A450nm U) was similar to that obtained in the typical carcinoids (mean, 104.5 A450nm U). All neuroendocrine tumors but the typical carcinoids showed high levels of telomerase activity (mean, 1,750.8 A450nm U). According to the telomerase hypothesis, typical carcinoid cells are mortal pre-M2 stage cells, but atypical carcinoid, large cell neuroendocrine lung carcinoma, and small cell lung carcinoma cells are immortal post-M2 stage cells. This finding may be of important prognostic significance in these kinds of tumors. Measurement of enzyme activity with a good morphologic control could be necessary in telomerase activity assay.