Bronchial carcinoid tumors metastatic to the sella turcica and review of the literature.

We review here the literature on neuroendocrine neoplasms metastatic to the pituitary and present an example of the disease. Metastasis of bronchial carcinoid tumors to the sellar region are rare. Herein, we describe the case of a 63-year-old woman who presented with constant cough and headaches. She had previously been operated for carcinoid tumor of the lung. During the preoperative investigation, a CT scan of the head revealed a sellar mass. Six months after a left lower lobectomy, the sellar lesion was removed by transsphenoidal surgery. The two tumors were evaluated by histology, immunohistochemistry and electron microscopy. Both showed identical morphologic features, those of carcinoid tumor. Immunohistochemistry revealed immunoreactivity for the endocrine markers, synaptophysin and chromogranin, as well as CD-56, serotonin, bombesin and vascular endothelial growth factor. The sellar neoplasm showed nuclear immunopositivity for thyroid transcription factor-1, supporting the diagnosis of a metastatic bronchial carcinoid tumor. In conclusion, this is the first report of a serotonin- and bombesin-immunopositive atypical bronchial carcinoid tumor metastatic to the sella.

Accelerating stem cell proliferation by down-regulation of cell cycle regulator p21.

BACKGROUND: Tissue engineering is often limited by the time required for culture expansion of cells necessary for scaffold seeding. Cell cycle regulators control entry and exit into the cell cycle and as such regulate cellular proliferation rates. The authors hypothesized that transient alteration in cell cycle regulators can be utilized as a means to accelerate stem cell proliferation. METHODS: Mesenchymal stem cells were harvested from wild-type mice and mice deficient in the cell cycle regulator p21. Wild-type cells were treated with small interfering RNA against p21 in two- or three-dimensional cultures in vitro. Cellular proliferation and the potential for cellular differentiation into the bone or fat lineage were assessed. RESULTS: Mesenchymal stem cells treated with small interfering RNA targeting p21 demonstrated a significant decrease in p21 protein and mRNA expression 96 hours after treatment. They also proliferated significantly faster than control cells (2.5 to three times) in both two- and three-dimensional culture. Similarly, cells harvested from p21-deficient mice demonstrated a significant acceleration in cellular proliferation. Inhibition of p21 expression was not associated with significant changes in spontaneous cellular differentiation. However, transient p21 inhibition promoted both osteoblastic and adipogenic differentiation when cells were exposed to differentiation medium. CONCLUSIONS: Transient inhibition of the cell cycle regulator p21 results in significant acceleration of mesenchymal stem cell proliferation without promoting spontaneous cellular differentiation. Exposure to differentiation medium results in increased cellular differentiation toward the osteoblast and fat lineage. Manipulation of cell cycle regulators may represent a novel means by which stem cell proliferation can be accelerated, thereby decreasing the time required for scaffold synthesis in tissue engineering.

Carotid body tumor mimicking adenocarcinoma on fine-needle aspiration.

We report an 86-year-old woman who presented with a 6-month history of a mass in the left side of her neck. MRI and MRI angiography favored a diagnosis of a neural tumor. FNAB showed a large cluster of cohesive, pleomorphic cells with intranuclear inclusion bodies; a diagnosis of adenocarcinoma was favored. At surgery, a 7 x 5 x 2.5 cm, firm, encapsulated mass was excised. Microscopically, the richly vascularized tumor had characteristics of a CBT, with large pleomorphic chief cells and spindle-shaped sustentacular cells in small, poorly formed nests. The chief cells were strongly immunoreactive for neuron-specific enolase and chromogranin, and focally positive for neurofilament, enkephalin, somatostatin, and beta-endorphin. The sustentacular cells were strongly immunoreactive for S-100 protein and glial fibrillary acidic protein and focally positive for vimentin. Ultrastructurally, the chief cells contained abundant neurosecretory granules. We emphasize that CBT must be included in the differential diagnosis of lateral neck masses. The distinction from adenocarcinoma is difficult on FNAB. The marked cytological atypia in an aspirate of a CBT does not indicate malignancy and may lead to an erroneous diagnosis.