Crystals and alpha-1-antitrypsin-reactive globoid inclusions in an islet cell tumor of the pancreas

Neuroendocrine carcinomas of the pancreas with 'Rhabdoid' features

Neuroendocrine carcinomas of the pancreas are rare neoplasms whose morphologic features generally mirror those seen in neuroendocrine tumors in other organs. Rarely, however, they may display unusual morphologic appearances that can introduce difficulties for diagnosis. We report four cases of primary neuroendocrine carcinomas of the pancreas (islet cell tumors) that were characterized by prominent "rhabdoid" features of the tumor cells. The lesions occurred in two men and two women 37-79 years of age who presented with symptoms of biliary obstruction and epigastric pain; one patient had recurrent gastric ulcers and an elevated gastrin level. The tumors were located in the head and tail of the pancreas and measured 2.5-4.5 cm in greatest diameter. Histologic examination revealed sheets of monotonous tumor cells with uniform round nuclei showing dispersed chromatin and containing abundant densely eosinophilic cytoplasmic inclusions that displaced the nuclei toward the periphery. In all cases, the rhabdoid elements appeared to merge with areas showing a more conventional neuroendocrine morphology. Immunohistochemical studies in all cases showed strong cytoplasmic positivity of the rhabdoid tumor cells for chromogranin, synaptophysin, and cytokeratin. Recognition of this unusual morphologic appearance is of importance to avoid mistaking these lesions for other types of malignant neoplasm.

Intracellular location and nuclear targeting of the Spi-1, Spi-2 and Spi-3 gene-derived serine protease inhibitors in non-secretory cells

Proteases and their inhibitors are indispensable for the regulated activation and/or degradation of structural and functional proteins involved in basic cellular processes, e.g. in cell cycle control, cell growth, differentiation and apoptosis. In this context the serine protease inhibitors derived from the murine Spi-1, Spi-2 and Spi-3 genes, and their human homologs, deserve reconsideration. Microsequencing data indicate that a fraction of the three serpins has the capability to constitute a well characterized proteinase K, high salt and SDS-stable complex which coisolates with DNA under salting out conditions from various cell and tissue types. This tight association with DNA isolated under conditions designed to deproteinize DNA efficiently points to an in situ preformed chromatin complex. Accordingly, in addition to their well known functions as 'serum protease inhibitors' the Spi-1 and Spi-2 gene-derived proteins appear to have intracellular functions as well. The involvement of the three serpins in chromatin complexes requires their nuclear translocation. Application of (enhanced) green fluorescent protein technology and optical section microscopy reveals that truncation of the N-terminal signal sequences of the Spi-1 and Spi-2 gene-encoded proteins is a prerequisite for their nuclear translocation while non-truncated fusion proteins are enriched at the nuclear indentation which is the site of the Golgi apparatus and the centrosome. The identification of new species of intracellular serpins is of potential interest with respect to accumulating evidence for serine protease inhibitor-dependent inhibition or prevention of apoptosis.

Alveolar soft-part sarcoma: a review of the pathology and histogenesis

The descriptive designation, alveolar soft-part sarcoma, continues to be used for this uncommon soft-tissue malignancy because an acceptable hypothesis for its histogenesis has not been advanced, despite studies with electron microscopy and immunohistochemistry. These techniques have, nevertheless, provided significant information that is useful in the differential diagnosis of the tumor and pertinent in speculation concerning its nature. The most intriguing ultrastructural feature is the secretory process that culminates in the formation of the distinctive cytoplasmic crystals. Myogenic differentiation has been favored in a number of recent reports on the basis of immunohistochemical findings and the presence of the crystals does not rule out the possibility, but accounts of immunoreactivity for the myogenic regulatory protein MyoD1 have not been confirmed in subsequent studies or in the authors' own staining of six cases.

A multifunctional protein: involvement of the alpha-1 serum protease inhibitor in SDS and high salt-stable DNA-protein complexes

Occasionally new and intriguing roles arise for proteins with well established functions. The alpha-1 serum protease inhibitor (alpha-1 PI) represents another example. Sequence identities exist in the alpha-1 PI and in a nuclear 52-kDa glycoprotein which is involved in resistant DNA-polypeptide complexes. The results of Western blots support the identity of the two proteins and immunocytochemical studies indicate the nuclear location of the alpha-1 PI. Consistently, e.g. Ehrlich ascites tumor cells express the alpha-1 PI, and the fusion protein between the alpha-1 PI and the green fluorescent protein from Aequorea victoria shows intracellular accumulation and partly nuclear location.

Identification of Charcot-Leyden crystals by electron microscopy

Observations of the ultrastructure of Charcot-Leyden crystals are sporadic in the literature. These crystals appear occasionally in clinical materials, however, and may pose diagnostic dilemmas if not correctly identified. Two cases in which unusual crystallike structures were seen on electron micrographs of specimens were evaluated for diagnostic purposes. These structures were tentatively identified as Charcot-Leyden crystals and subsequently were confirmed as such by immunoperoxidase labeling. The cases are reported together with a review of the ultrastructure, histology, immunology, and natural history of Charcot-Leyden crystals.

Upper abdominal neoplasms: an introduction and selected references

The organs in the upper half of the abdominal cavity can give rise to a highly heterogeneous collection of neoplasms that encompasses a broad spectrum of clinical features, light microscopic appearances, immunostaining properties, and fine structure. Because of the anatomic proximity of the viscera in this region, the differential diagnosis of an upper abdominal mass may include consideration of tumors that arise from the stomach, duodenum, liver, kidney, adrenal, and pancreas. There are many distinctive ultrastructural features among the various tumors that can be used effectively by the diagnostic electron microscopist, but it is also important to take into account the considerable overlap in fine structure that occurs among different tumors and among similar tumors from different organs. In the session on upper abdominal neoplasms, the electron microscopic characteristics of the common tumors of each viscus were reviewed before the presentation of individual case studies that incorporated original observations and illustrated some unusual entities. The selection of cases that follows is inevitably small and arbitrary, but the cases demonstrate the contribution that electron microscopy can make in the study of an upper abdominal mass and illustrate some of the similarities that can be encountered among tumors of different organs.

Membrane-bound cytoplasmic crystals, similar to those in alveolar soft part sarcoma, in a human muscle spindle

Membrane-bound cytoplasmic crystals were found in the intrafusal fibers of a muscle spindle from a patient with neurogenic atrophy. The crystals have a periodicity of 10 nm and an intersecting axis angle of approximately 80 degrees. This makes the crystals similar to those described in alveolar soft part sarcoma (ASPS). Because the crystals in ASPS may not be quite as specific as previously believed, and because similar crystals have been described in various other neoplasms, the present findings should not be taken as evidence for a muscle spindle derivation for ASPS.

Intraluminal crystalloids in prostatic adenocarcinoma. Immunohistochemical, electron microscopic, and x-ray microanalytic studies

Histochemical, immunohistochemical, electron microscopic, and x-ray microanalytic studies were performed on crystalloids within glandular lumina of adenocarcinomas of the prostate. In a review of light microscopic sections of 343 prostatic adenocarcinomas, unequivocal crystalloids were identified in 35 cases (10.2%). Immunohistochemical and ultrastructural studies revealed distinct differences between these crystalloids and the Bence Jones crystals of multiple myeloma: anti-kappa and anti-lamda immunostaining was negative, and the characteristic lattice-like architecture of Bence Jones crystals was not seen. Differences from corpora amylacea also were demonstrated. X-ray microanalysis did not elucidate the nature of the prostatic crystalloids, and their biochemical composition and mode of formation remain uncertain. Detection of the crystalloids in light microscopic sections nevertheless can aid in the diagnosis of prostatic adenocarcinoma, particularly when the tissue is distorted by crushing artifact, or if the tumor is so well-differentiated that it can be confused with atypical hyperplasia or inflammatory atypia. When intraluminal crystalloids are detected in prostatic glands that appear histologically benign or atypical, study of additional levels or a repeat biopsy should be undertaken.