Cardiac neuroendocrine tumor with absence of sustentacular cells: immunohistochemical and ultrastructural findings.

A 68-year-old male presented with increased shortness of breath and intermittent chest pain. Cardiac catheterization along with echocardiogram imaging demonstrated 3-vessel coronary artery disease with severe left ventricular dysfunction and critical aortic stenosis. During coronary artery bypass surgery, a tumor was identified at the sulcus between the aorta and the right atrial appendage. This highly vascular tumor extended over the right coronary artery, prompting biopsy and further resection. Light microscopic evaluation showed packets of uniform round neoplastic cells without evidence of necrosis or increased mitotic figures. Immunohistochemical studies were positive for synaptophysin and weakly positive for chromogranin. Pankeratin, S-100, and GFAP stains were all negative. Ultrastructural examination of the neoplasm demonstrated numerous electron-dense secretory granules within the cytoplasm of the tumor cells. These secretory granules varied in size from 60 to 210 nm, with halos encircling many of them, suggesting the likelihood of epinephrine or norepinephrine granules. Within the specimen, abundant vascular spaces were identified, but no sustentactular cells were present. The patient agreed to undergo genetic testing, and a mutation in the succinate dehydrogenase complex subunit B (SDHB) was identified. This confirmed the molecular diagnosis of hereditary paraganglioma/pheochromocytoma syndrome. Now two years out from surgery, this patient continues to be asymptomatic in spite of the fact that his tumor was only partially resected.

Kaposiform hemangioendothelioma arising in the deltoid muscle without the Kasabach-Merritt phenomenon.

Kaposiform hemangioendothelioma (KHE) is a rare tumor that occurs nearly exclusively during infancy and childhood. It has features common to both capillary hemangioma and Kaposi sarcoma and for that reason many terms have been used for these tumors including "Kaposi-like infantile hemangioendothelioma" and "hemangioma with Kaposi sarcoma-like features." KHE typically presents as an ill-defined, red to purple, indurated plaque and is often complicated by the Kasabach-Merritt phenomenon (KMP), a condition of severe thrombocytopenia and consumptive coagulopathy. Knowledge of the radiological findings of this uncommon tumor might be helpful for diagnosis. We present the MRI features of a case of KHE with neither typical skin lesions nor the Kasabach-Merritt phenomenon.

Dumbbell-shaped leiomyosarcoma of the inferior vena cava with foci of rhabdoid changes and osteoclast-type giant cells.

An inferior vena cava (IVC) tumor was incidentally found in a 67-year-old Japanese man. The resected tumor was lobulated and multinodular, measuring 14.0 x 6.5 x 7.0 cm, showing a dumbbell-shaped appearance with a central constriction. The tumor showed both intra- and extra-luminal growth. The tumor was primarily composed of well-differentiated leiomyosarcoma. Spindle tumor cells in the well-differentiated area were positive for vimentin, muscle actin, alpha-smooth muscle actin, and desmin. Foci of rhabdoid cells and osteoclast-type multinucleated giant cells were also found. Rhabdoid cells ultrastructurally had paranuclear aggregates or whorls of intermediate filaments that were positive for vimentin, low molecular weight cytokeratin, and desmin. Osteoclast-type multinucleated giant cells were positive for only CD68 antigen, suggesting a reactive histiocytic lineage. To the best of our knowledge, this is the first case of IVC leiomyosarcoma accompanied by both rhabdoid tumor cells and osteoclast-type reactive multinucleated giant cells. These unusual features should be kept in mind in the diagnosis of dumbbell-shaped retroperitoneal tumors that involve the IVC.

Perivascular myoma: case report with immunohistochemical and ultrastructural studies.

A subcutaneous myopericytoma-type perivascular myoma arising in the elbow of a 61-year-old woman is described. The tumor was well demarcated and consisted microscopically of small ovoid and spindle cells arranged in a concentric fashion, surrounding small to medium-sized vessels and imparting a superficial resemblance to hemangiopericytoma. In some areas, the cellular whorls were separated by myxoid stroma. Cells located between cellular whorls appeared immature with scant cytoplasm but did not show distinct nuclear anaplasia, increased mitoses or foci of necrosis. Immunohistochemistry showed that constituent cells were positive for alpha-smooth muscle actin and desmin. Electron microscopy disclosed that the immature-looking cells, as well as the ovoid and spindle-shaped cells, possessed focal densities along with thin filaments, subplasmalemmal densities, pinocytotic vesicles and an external lamina. These ultrastructural and immunohistochemical features indicate a myoid nature of pericytic cells and justify this type of neoplasm being categorized as perivascular myoid tumor.

Intimal-type primary sarcoma of the aorta. Report of a case with evidence of rhabdomyosarcomatous differentiation.

We report an intimal sarcoma presenting as an aortic aneurysm. A 68-year-old man suffered from chest pain and speech disturbance. Computed tomography showed a sacciform aneurysm of the aorta, which was resected, revealing a polypoid tumour measuring 1.5x2x2.5 cm projecting into the lumen. This proved to be a poorly differentiated high-grade sarcoma having morphological, immunophenotypic and ultrastructural features consistent with rhabdomyosarcomatous differentiation. Primary sarcomas of the aorta are extremely rare. Many cases have been diagnosed as "intimal" on the basis of their site of origin, and they are not easy to classify from their histological pattern. Electron microscopy and the use of a more comprehensive panel of immunohistochemical markers should be applied in the histological classification of"intimal" sarcoma.

Vascular leiomyoma of the mesentery in a dog.

A 4-year-old male, miniature Schnauzer dog showed two large masses in the mesentery at necropsy. Histological examination of both masses revealed plain smooth muscle tumour cells intermingled with thick-walled blood vessels. The bundles of tumour cells often extended from the periphery of the vessels. Mitotic figures were rare. From these findings, the tumour was diagnosed as a vascular leiomyoma (angiomyoma), previously unreported in animals. The term, vascular leiomyoma, was proposed to describe this tumour in order to avoid confusion with hamartomatous angiomyoma.

Intravascular malignant T-cell lymphoma (malignant angioendotheliomatosis) in a cat.

A 7-year-old spayed female Siamese cat was presented with a 7-day history of ataxia, circling to the right, and involuntary micturition and defecation. Cerebrospinal fluid analysis showed increased protein content and relative eosinophilia. At necropsy, there was flattening of the cerebral cortical gyri of the right frontal and parietal lobes, and both kidneys had multiple wedge-shaped cortical indentations. Histologically, the cerebral cortex contained several extensive malacic foci, and the kidneys had multifocal parenchymal degeneration and atrophy. There was multifocal partial to complete thrombosis of renal interlobar arteries and of the right middle cerebral artery and meningeal branches; these thrombi contained large anaplastic round cells, which often invaded the arterial wall. Many smaller vessels within the kidneys and brain were occluded with clusters of similar cells, without thrombosis or vascular wall invasion. The neoplastic round cells had immunohistochemical staining properties of T lymphocytes.

Leiomyosarcoma of the pulmonary vein: case report with immunohistochemical and ultrastructural findings.

We report a case of neoplasia of pulmonary vein in a 45-year-old woman who presented with increasing dyspnea. As a consequence, the neoplasia filled the entire left atrium and appeared to be attached to the left superior pulmonary vein on surgical excision. Histologically, it was composed of a proliferation of sarcomatous cells, with a high mitotic rate and diffuse immunohistochemical positivity for smooth muscle actin, consistent with a leiomyosarcoma. The microscopic, immunohistochemical, and ultrastructural findings are discussed.