Search

Small cell neuroendocrine carcinoma (SCNEC) of the urinary bladder is a rare but aggressive neoplasm that usually exhibits neuroendocrine differentiation. Here, the authors report a case of SCNEC in an 80-year-old man. The patient had gross hematuria and nodular mass involving the wall of the urinary bladder. Total cystectomy was done. The tumor consisted of small, uniform, round, and spindled-shaped cells with chromatin dark nuclei and numerous mitotic figures. The cells were reactive for chromogranin, neuron-specific enolase (diffuse), and keratin (focal). Ultrastructural studies revealed neurosecretory granules and intermediate filaments. The diagnosis of SCNEC with focal high-grade urothelial component was established. No metastasis was found at the time of diagnosis and the patient refused further chemotherapy or radiotherapy. The histogenesis, differential diagnosis, and prognosis of SCNEC of the urinary bladder were discussed.

Eighty-two mesenchymal tumors of the gastrointestinal tract were examined by electron microscopy for the purposes of subtyping for diagnostic precision and of understanding cellular differentiation. Tumors were subclassified into leiomyoma/leiomyosarcoma, tumors of the interstitial cell of Cajal (equivalent to traditionally defined GISTs [Miettinen et al. Hum Pathol. 1999; 30:1213-1220; Mod Pathol. 2000; 13:1134-1142]), gastrointestinal autonomic nerve tumors (GANTs), and fibroblastic and myofibroblastic tumors, using criteria from the literature. Leiomyoma/leiomyosarcoma were diagnosed by myofilaments, attachment plaques, plasmalemmal caveolae, and lamina; GIST by processes or cell bodies full of intermediate filaments, solitary focal densities amid intermediate filaments, attachment plaques with incomplete lamina, scarce myofilaments, and smooth endoplasmic reticulum; GANTs by neuroendocrine granules, cell bodies/processes full of intermediate filaments (more rarely microtubules), and smooth endoplasmic reticulum; fibroblastic/myofibroblastic tumors by abundant rough endoplasmic reticulum, myofilaments, and fibronexuses. Seventy-three tumors (89%) were successfully subclassified, as 5 leiomyoma/leiomyosarcoma (6%), 36 GISTs (44%), 22 GANTs (27%), 10 fibroblastic and myofibroblastic tumors (12%). Results indicated overlap between poorly differentiated leiomyosarcoma and GIST, and between GIST and GANT. GANT is emphasized as a neuronal tumor identifiable by electron microscopy, and thereby distinguishable from GIST.

Two cases of the diffuse type of giant-cell tumor of the tendon sheath (GCTTS) are described. Both tumors arose in the vicinity of large joints of the lower extremity, showing similar clinical and radiological features. Histologically, a proliferation of polygonal mononuclear cells was seen, together with osteoclastlike giant cells, foam cells, and siderophages. The tumors were poorly delineated, displaying an infiltrative pattern into the neighboring soft tissues. Immunohistochemically, strong expression of vimentin, neuron-specific enolase, A1-antitrypsin, and CD68 was found in both mono- and multinucleated tumor cells. At the ultrastructural level, mononuclear cells revealed a diverse morphology, displaying features of histiocytelike and fibroblastlike cells, with the former being more numerous. Scarce neurosecretorylike granules, made up of electrondense membrane-bound material, were found in the cytoplasm of the mononuclear cells. Cytogenetic analysis of one case shows the presence of a clonal population with 47 chromosomes and two different translocations, t(2;3) and der(8) t(8;12). Present findings provide further support regarding the neoplasic nature of this tumoral entity.

Middle ear adenoma (MEA) is a rare tumor postulated to take origin from the lining epithelium of the middle ear cavity. The authors report on a case of MEA arising in a 53-year old woman suffering from a sensation of fullness in her left ear, otalgia, and light left-sided hearing loss. Histopathologically, the lesion was composed of cuboidal and polygonal cells displaying a trabecular, tubulo-glandular, and solid pattern of growth. Immunohistochemically, neoplastic cells diffusely stained with anti-vimentin antibodies and were focally positive for chromogranin A, neuron-specific enolase, lysozyme, and cytokeratins AE1/AE3. The majority of tumor cells showed weak and diffuse staining with both anti-PP and anti-ACTH antibodies and intense positivity with anti-glucagon and anti Leu-7 antibodies. Ultrastructural investigation revealed both mucinous-glandular and neuroendocrine differentiation. The authors suggest that the appropriate terminology would be adeno-carcinoid or amphicrine tumor of the middle ear rather than "adenoma," a term that does not reflect its dual nature.

Prolonged storage of Karnovsky's fixative, at both 4 and -20 degrees C, is possible in the diagnostic electron microscopy setting. Ultrastructural detail was not compromised in specimens processed in fixative that had been stored for 6 months. Evidence of smooth muscle and neuroendocrine differentiation was present in the form of actin filaments/dense bodies and neurosecretory granules, respectively. No difference in preservation was detected between specimens fixed in freshly prepared Karnovsky's fixative and fixative that had been stored at either 4 or -20 degrees C for up to 6 months. Thus, community hospitals can be provided with Karnovsky's fixative on a semiannual basis for surgical pathology specimens that may require electron microscopy for diagnosis.

The endometrioid-like variant of ovarian yolk sac tumor is a rare neoplasm composed partially or completely of glandular tissue resembling endometrioid carcinoma, but identifiable histologically and immunohistochemically as an extraembryonic endodermally differentiated germ cell tumor. Only nine examples of this neoplasm have been published previously, and none was studied by electron microscopy. One of these rare neoplasms, the first documented to have foci of carcinoid, has recently been observed and studied ultrastructurally. Electron microscopic observations showed that the main component of the neoplasm had glandular epithelial cells with nuclear and cytoplasmic features difficult to distinguish from the cells of Müllerian endometrioid and endometrial adenocarcinoma, but a minor component of mucinous adenocarcinoma was confirmed as intestinal by the epithelial cells having characteristic microvilli with filamentous cores and rootlets. In addition, neuroendocrine cells present in the glands and in nests were readily identified ultrastructurally by their dense-core granules. Electron microscopy may be useful in supplementing light microscopic and immunohistochemical examination of this variant of yolk sac tumor.

We have investigated various tissue fixation and embedding protocols in an effort to allow expanded use of immunoelectron microscopy in diagnostic surgical pathology. A sample of normal human small bowel mucosa was processed using seven different methods for subsequent postembedding localization of chromogranin A. In addition, several archival cases of neuroendocrine tumors previously fixed and routinely embedded for electron microscopy, stored in formalin, or snap-frozen were retrieved and variously processed for chromogranin A localization at the ultrastructural level. Precise localization of chromogranin A in dense core granules was achieved with protein A-gold on sections from all of the processing methods. The methods included retrieval into mild fixative of previously formalin-fixed or snap-frozen tissues followed by embedding in Lowicryl K4M (Polysciences Ltd., Eppelheim, Germany). Thus, tissue processed without foresight of the need for immunoelectron microscopic localization can be successfully used. Since embedding of tissues in Lowicryl K4M has been shown to preserve a variety of antigens, it may prove to be a superior resin for use in diagnostic immunoelectron microscopy.

Neuroendocrine neoplasia represents a heterogenous entity with variable morphologic light microscopic expressions. In many cases a definite diagnosis is easily made by light microscopic examination, but in some cases this does not suffice. In the latter instances, immunocytochemistry, ultrastructural examination, or both are required to diagnose a neuroendocrine neoplasm. However, basing a diagnosis of neuroendocrine neoplasia exclusively on the results obtained from immunocytochemical or ultrastructural evaluation of these tumors may not be entirely accurate in some instances. Ultrastructural immunolabeling plays a key role in accurately defining localization of immunoreactive substances in well-characterized neuroendocrine neoplasms, can assess colocalization of antigenic epitopes, helps define specificity and significance of immunocytochemistry results obtained at the light microscopic level, and is more sensitive than light microscopic immunocyto-chemistry. Some evolving diagnostic entities can be further characterized by utilization of ultrastructural labeling techniques. Controversies concerning the neuroendocrine nature of electron-dense structures identifiable at the ultrastructural level can be readily and accurately resolved. By providing a way to evaluate combined immunomorphologic parameters, ultrastructural immunogold labeling can settle important questions pertaining to neuroendocrine neoplasia. The present article illustrates a series of cases where the above-mentioned applications were tested.

Immunogold ultrastructural localization of chromogranin A in secretory granules within tumor cells provides convincing evidence of endocrine or neuroendocrine differentiation. A modified immunogold method (designed for use on osmicated tissue) produced positive labeling of small granules not only in well-differentiated tumors but also in poorly differentiated small cell tumors primary in lung, cervix, and skin; only a proportion of granules in some of the tumor cells were positively labeled. Many non-small cell lung tumors often stain focally positive for chromogranin A at the light microscopy level, and such tumors may also contain sparse, small, dense granules. Because positive labeling could not be demonstrated over small granules in non-small cell lung tumors, the theory that such tumors are neuroendocrine in type may be erroneous.

This overview emphasizes the utility of the uranaffin reaction in the diagnosis of tumors derived from neuroendocrine cells. The history, cell organelle specificity, tissue specificity, pH requirements, and detailed procedure of the uranaffin reaction is provided. Uranaffin-positive granules are also identified within the NS granules of the stem cell paraneuron (archiparaneuron) of coelenterates, and a hypothetical evolutionary scheme depicting the possible origins of the key biochemical features of the advanced mammalian NS granule is included. The role of nucleotides, a major component of true NS granules, is discussed. A possible intragranular function of ATP as a regulator of osmotic pressure and the extracellular physiologic effects of secreted intragranular nucleotides are discussed in some detail.

For full diagnostic use to be made of the neurosecretory granule, the range of sizes, forms, and staining qualities for this cytoplasmic organelle, along with the extent of its expression in various neoplasms, must be established. Neurosecretory type granules occasionally occur in nonneuroendocrine tumors. A series of carcinoids of the lung provides a model for assessing the morphologic types of cytoplasmic granules identified by antibodies to chromogranin A and immunogold labeling. The results show that granule structure in tumors is pleomorphic. Despite having sizes within the expected range, many labeled and, indeed, unlabeled secretory granules are atypical, particularly in structural form. Cell-to-cell variation in the proportion of even typical neurosecretory granules labeling for chromogranin A is the rule. Studies correlating biochemical, immunohistochemical, electron microscopic, and perhaps in situ hybridization characteristics are required to define better the criteria for unequivocal identification of neurosecretory granules in tumors.

A tumorlet of the lung is a minute tumorlike lesion found in damaged lungs in close association with the bronchioles. Histochemical and ultrastructural studies identify proliferating cells in the tumorlets as Kultschitzky-type cells. However, the pathological significance of the tumorlets, whether they are hyperplastic or neoplastic, is still controversial. Previous ultrastructural studies on the tumorlets have been carried out on formalin-fixed lung tissues. The case examined in this study was of typical tumorlets found in a so-called middle lobe syndrome of the lung of a 52-year-old woman. Tumorlets were located within the bronchiolar mucosa surrounded directly by a basal lamina and by the bronchiolar nonendocrine epithelial cells. There were no signs of invasion into the surrounding connective tissues or into lymphaticlike spaces. Between the covering bronchiolar epithelial cells and the subjacent proliferating Kultschitzky cells, specific sites of cell-to-cell attachment were noted. This finding, in addition to previously reported clinicopathological characteristics, indicates that the proliferating Kultschitzky-type cells in the tumorlets might be non-neoplastic and that tumorlets are due to hyperplasia of pure Kultschitzky-type cells, thus resembling neuroepithelial bodies of the lung.

A case of poorly differentiated intestinal-type gastric adenocarcinoma with ultrastructural evidence of a neuroendocrine differentiation, including rare neurosecretory granules and microtubules, is reported. Tumor cells often showed irregularities of the nuclear contour ranging from invaginations to nuclear projections and pockets. Intranuclear and intranucleolar tubular inclusions were observed, and their morphogenetic relation with the nuclear envelope is discussed. This appears to be the first report describing intranucleolar tubular inclusions in a human tumor.

The ultrastructural patterns of neuroendocrine (NE) differentiated breast carcinomas are analyzed and discussed. Reports in the literature describe wide variations in the size of observed dense-core membrane-bound granules and discrepancies in their interpretation. In the present study 24 cases of breast carcinoma with recognized morphologic, histochemical, and immunocytochemical features of NE tumors were investigated. Five different types of dense-core granules of neurosecretory (NS) type (confirmed by the ultrastructural localization of chromogranin A) and five different cell types were recognized. Some amphicrine cells were found to contain both mucin and NS granules. Another notable ultrastructural feature of breast NE carcinomas was the presence of clear vesicles of presynaptic type, which correlated with expression of synaptophysin.

A neuroendocrine tumor with ultrastructural "anemone cell" features in lymph nodes is reported. A primary tumor was not identified, but clinical and morphologic features suggested a metastatic Merkel cell carcinoma. The anemone cells were dissociated, lacked intercellular junctions, and contained cytoplasmic intermediate filament aggregates that immunohistochemically reacted with keratins, but they had only sparse neurosecretory granules. Where the tumor cells had infiltrated beyond the lymph nodes, however, they formed a trabecular pattern. A fine-needle aspirate from a later recurrence of the tumor lacked anemone cell features and was ultrastructurally typical of a Merkel cell carcinoma, with neurosecretory granules and intercellular junctions both being evident. The concept of anemone cell tumors and the morphologic variations determined by site are discussed.

Ultrastructural differences in size of granules of adjacent Merkel cells belonging to normal skin of three patients are demonstrated. The differences, apparent on simple examination of micrographs, were confirmed using morphometric and statistical analysis. Differences are statistically significant (p less than or equal to 0.001) for maximum diameter and granular area. The existence of a NE (Merkel) cells system or population in the skin similar to that observed in diverse epithelial sheets of the human body, is suggested.

Eight mucinous carcinomas of the breast were studied by light microscopy and immunohistochemistry; one was studied by electron microscopy. All 8 cases had abundant, relatively clear cytoplasm that contained mucin. Cells were argyrophil positive and argentaffin negative. Eight cases were positive for neuron specific enolase (NSE), 5 cases for serotonin, 1 case for serotonin and somatostatin and 2 cases for serotonin, somatostatin, and gastrin. None had clinical evidence of abnormal neuroendocrine function. Three patients had axillary lymph node metastases. Only 1 of 5 patients in whom there was clinical followup died of her disease. Electron microscopy of one case showed abundant intracytoplasmic and extracellular mucin, round and pleomorphic dense-core granules, numerous cell processes, and aggregates of intermediate filaments. These cases expand the histologic spectrum of breast carcinomas which may show neuroendocrine differentiation.