Prevalence of double pituitary adenomas in a surgical series: Clinical, histological and genetic features.

BACKGROUND: The term double pituitary adenomas (DPA) is usually referred to those rare lesions showing two distinct cellular components. Genetic background may sustain the proliferation of more than one cell at the same time but no information is available on the presence of aip mutations in these patients. AIM: We report the prevalence and the endocrinological, neuroradiological, histopathological and genetic features of DPA detected in a large surgical series. The contribution of pituitary transcription factor immunostains in DPA was also evaluated. SUBJECTS AND METHODS: One-hundred-forty-four patients undergoing surgery for tumors of the sellar region were evaluated. Histopathology, immunohistochemistry and the mutational analysis for the entire coding region of the AIP and MEN1 genes were performed. RESULTS: One-hundred-seventeen patients out of 144 had a pituitary adenoma. DPA was found in 3 (2.6%) out of 117 patients with pituitary adenoma. Immunohistochemistry and transcription factors analysis demonstrated two not yet described histotype associations in DPA. The coexistence of somatotroph-lactotroph and silent mammosomatotroph histotype in 1 case and the coexistence of sparsely granulated lactotroph and null cell adenomas in the remaining two cases were first identified. Sequencing data for the coding region of the aip and the menin gene resulted in wild type sequences in all patients with DPA. CONCLUSIONS: The prevalence of DPA observed in our unselected surgical series is not negligible (2.6%). Furthermore, the evaluation of the treatment outcome would suggest that the clinical management of DPAs requires a careful diagnostic approach and follow- up.

Occurrence of medullary thyroid carcinoma, bronchial carcinoid tumor, and papillary thyroid carcinoma in a family bearing the RET G691S polymorphism.

RET mutations play an important role in the development of human neuroendocrine tumors. The prevalence of the RET polymorphism G691S of exon 11 is higher in patients with medullary thyroid carcinoma (MTC) as compared to the general population. A weak association between RET polymorphisms and sporadic papillary thyroid carcinoma (PTC) has also been described. We hereby describe the association of MTC, bronchial carcinoid tumor, and PTC in a familial setting. A 75-yr-old woman developed MTC 7 yr after successful treatment of a bronchial carcinoid. Serum calcitonin was 12.9 pg/ml with a peak response to pentagastrin (151.0 pg/ml). The patient underwent total thyroidectomy and a genetic mutational analysis of the RET gene. Histological evaluation confirmed MTC with no evidence of lymph nodes involvement. After thyroidectomy serum calcitonin was <2.0 pg/ml. A germline missense mutation at codon 691 in exon 11 of the RET gene was found. The mutational analysis was extended to the patient's offspring, and her daughter was found to bear the G691S polymorphism of RET. Wild type RET gene was found in the son. The daughter, who showed a nodular goiter, autoimmune thyroiditis and normal serum calcitonin, also underwent thyroidectomy. Histologic examination of the thyroid revealed an incidental PTC. This is the first description of a bronchial carcinoid tumor occurring in association with MTC. The occurrence of apparently unrelated NET in the same subject, or within a family, should be regarded as a challenge for deeper investigations into the possible oncogenic role of this genetic alteration.

Functional analyses and molecular modeling of two c-Kit mutations responsible for imatinib secondary resistance in GIST patients.

Imatinib-acquired resistance related to the presence of secondary point mutations has become a frequent event in gastrointestinal stromal tumors. Here, transient transfection experiments with plasmids carrying two different KIT-acquired point mutations were performed along with immunoprecipitation of total protein extracts, derived from imatinib-treated and untreated cells. The molecular mechanics/Poisson Boltzmann surface area computational techniques were applied to study the interactions of the wild-type and mutated receptors with imatinib at the molecular level. Biochemical analyses showed KIT phosphorylation in cells transfected with vectors carrying the specific mutant genes. Imatinib treatment demonstrated that T670I was insensitive to the drug at all the applied concentrations, whereas V654A was inhibited by 6 microM of imatinib. The modeling of the mutated receptors revealed that both substitutions affect imatinib-binding site, but to a different extent: T670I substantially modifies the binding pocket, whereas V654A induces only relatively confined structural changes. We demonstrated that T670I and V654A cause indeed imatinib-acquired resistance and that the former is more resistant to imatinib than the latter. The application of molecular simulations allowed us to quantify the interactions between the mutated receptors and imatinib, and to propose a molecular rationale for this type of drug resistance.

PDGFRalpha, PDGFRbeta and KIT expression/activation in conventional chondrosarcoma.

Chondrosarcomas represent 20% of all primary bone sarcomas, and many studies have attempted to unravel molecular targets for future development of new therapies. The aim of this study was to investigate the expression/activation of PDGFRalpha, PDGFRbeta and KIT receptor tyrosine kinases (RTKs) as potential therapeutic targets in conventional central primary chondrosarcomas (CCS). The expression of PDGFRalpha, PDGFRbeta and KIT RTKs was detected in 16 CCSs using immunohistochemistry (IHC), and their level of expression and activation status were analysed by immunoprecipitation and western blot experiments. PDGFRalpha, PDGFRbeta and KIT cDNAs were screened to verify the presence of activating mutations and the presence of the cognate ligands was analysed by means of RT-PCR. RTK gene amplification was further studied by means of fluorescence in situ hybridization (FISH) analysis. The immunophenotyping and biochemical analyses showed that the CCSs co-expressed PDGFRalpha and PDGFRbeta, with the latter showing definitively greater protein expression and phosphorylation levels. PDGFRbeta was expressed but not activated in control healthy joint cartilage, in line with no PDGFB detection. Conversely, the KIT gene product did not seem to play a relevant role. These findings, in the absence of activating mutations or an abnormal genomic profile and the presence of PDGFA and PDGFB expression, are consistent with an autocrine/paracrine loop activation of the corresponding receptors. The CCS gene profile described here offers a rationale for the use of RTK inhibitors alone or in combination with chemotherapy, and supports further investigation of RTKs and their downstream signals.

Gene expression profile identifies a rare epithelioid variant case of pleomorphic liposarcoma carrying FUS-CHOP transcript.

AIMS: To describe a tumour with morphological and immunophenotypic characteristics of epithelioid variant of pleomorphic liposarcoma. Pleomorphic liposarcoma is a very rare variant of liposarcoma defined morphologically by the presence of pleomorphic lipoblasts showing peculiar epithelial-like features that can be confused with primary or metastatic carcinoma. METHODS AND RESULTS: Molecular analysis demonstrated for the first time the presence of FUS-CHOP transcript in this liposarcoma variant. Microarray analysis revealed a gene expression profile related to a more aggressive tumour type when compared with other myxoid/round cell liposarcomas. CONCLUSIONS: The present data show that the epithelioid variant of pleomorphic liposarcoma represents a further variant of myxoid liposarcoma sharing the FUS-CHOP fusion transcript but carrying a distinct expression profile, in keeping with its aggressive clinical course.