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Gastric inverted hyperplastic polyp (IHP) is a rare type of gastric polyp, and is characterized by downward growth of the hyperplastic mucosal components into the submucosa. To the best of our knowledge, 16 gastric IHP cases have been described in the English literature, but the pathogenesis has not been established. We report the clinical and pathological findings of four gastric IHP cases. The lesions were mainly composed of hyperplastic foveolar-type glands with focal cystic dilatation. Pyloric type glands, endocrine cells, acinic cell metaplasia, and smooth muscle bundles were also seen as components of the polyp. Two cases (cases 1 and 4) coexisted with multifocal gastritis cystica profunda (GCP) and gastric adenocarcinoma. Case 4 furthermore exhibited an intermediate form between IHP and GCP. We suggest that IHP may be GCP associated with exaggeratedly hyperplastic and metaplastic changes. In case 4, the coexisting gastric carcinoma was mainly located in the submucosa, whilst the mucosal component was minimal. Five out of twenty reported gastric IHP cases, including our cases, coexisted with gastric adenocarcinoma. These facts would lead us to further investigate the relation between gastric IHP and carcinoma.

To clarify whether scattered endocrine cells in pancreatic ductal adenocarcinoma are neoplastic or not, we immunohistochemically studied 29 cases of invasive pancreatic ductal adenocarcinomas, 17 with metastases, for chromogranin A, insulin, glucagon, pancreatic polypeptide, serotonin, gastrin, laminin, and Ki-67. Endocrine cells were found in primary sites in 24 cases (82.3%), where endocrine cells showed at least a visibly close location to adjacent islet cells. Although endocrine cells in neoplastic glands were within the neoplastic basement membrane, endocrine cells were not seen in invasive sites beyond the pancreas where islets were not present. Endocrine cells in neoplastic glands were reactive for two or three of the islet hormones in all cases, and different types of hormonal reactivity was recognized in the same neoplastic gland or the same cluster of neoplastic glands in 22 (91.7%) cases, thus suggesting a close relation with islets. Ki-67 did not stain any endocrine cells in ten of the adenocarcinomas studied. In three (10.3%) cases, endocrine cells were found in the intraductal extensions. They may have pre-existed in non-neoplastic ducts. In 17 cases with metastatic sites, all but one had no endocrine cells in the metastases. Serotonin-positive cells were found in one metastatic lymph node in one case. We concluded that most endocrine cells seen in ductal adenocarcinomas of the pancreas are non-neoplastic and are derived from the surrounding islets. Some neoplastic endocrine cells may exist, though their frequency is low.

We report a case of a 17-year-old man with a spindle cell tumor in the occipital subcutaneous tissue. The enucleated tumor, measuring 2.5 x 2.0 x 1.0 cm, had a broad-bean shape and well circumscribed border and was localized to the subcutis without dermal involvement. Microscopically, the tumor was composed of uniform spindle cells showing interlacing bundle formation and a herringbone pattern. The neoplastic cells were separated by collagen fibers in parallel fashion, the amount of which varied with different areas in the tumor. Mitotic figures were eight mitoses per 50 high-power fields in number. The neoplastic cells were positive for vimentin, Factor-XIIIa, alpha-smooth muscle actin and CD34, but negative for desmin, calponin, high molecular weight caldesmon, smooth muscle myosin heavy chain, collagen type IV, laminin and S-100 protein. These immunohistochemical results indicated that the neoplastic cells showed differentiation toward fibroblasts/myofibroblasts/dendritic interstitial cells. Although more than 50% of the neoplastic cells were positive for CD34, the present tumor should be diagnosed as well differentiated fibrosarcoma, adult type, rather than extrapleural solitary fibrous tumor and fibrosarcomatous areas of dermatofibrosarcoma protuberans, on the basis of routine microscopic findings mentioned above.

An immunohistochemical study of nine cases of chondroid syringomas/mixed tumors of the skin was performed to elucidate the nature of the so-called neoplastic myoepithelial cells (NMEC) in tumor tissues. These nine tumors contained NMEC of considerable variability in number from one tumor to another. These NMEC were classified into three types: (i) hyaline cells (plasmacytoid cells); (ii) spindle NMEC; and (iii) polyhedral cells. They showed different immunostaining patterns, as the following describes. Cytokeratin 14 was positive in most of the spindle NMEC and a large number of the polyhedral cells, and in a small number of the hyaline cells. Concerning low molecular weight cytokeratins, most of the hyaline cells showed immunoreactivity, whereas they were negative in many of the spindle NMEC and were expressed only in a small number of the polyhedral cells. alpha-Smooth muscle actin and muscle-specific actin were positive in the spindle NMEC but negative in any of the hyaline cells and polyhedral cells. These findings strongly indicate that the hyaline cells and the spindle NMEC are of the simple epithelial and myoepithelial types, respectively. The findings also suggest that the polyhedral cells show differentiation toward basal cells of the sweat gland dermal ducts or myoepithelial cells.

To investigate the pathogenesis of congenital hydrocephalus the brains of HTX rats aged between 16 days and 4 weeks and the brains of normal Wistar rats of the same ages were examined. In the fetal HTX rat brains, the lateral ventricles were symmetrically dilated from 20 days of gestation. The neuroepithelium bordering the ventricles showed thinning with cellular disarrangement and deformity. Similar neuroepithelial abnormalities were also found in the lateral ventricles of the HTX rat brain with no macroscopic signs of hydrocephalus at 20 days of gestation. The neuroepithelium showed flattening of the cells, widening of the intercellular spaces, formation of microvilli on the detached lateral cell surfaces, and frequent macrophage infiltration. On the other hand, the neuroepithelial cells of the third ventricle and the aqueduct were affected less severely or showed no significant abnormalities. Immunohistochemically, most of the neuroepithelium and ependyma of the lateral ventricles were positive for vimentin in both prenatal and postnatal hydrocephalic HTX rats, while a small number or none of those in normal control rats were positive. These morphological changes suggested that preferential involvement of the lateral ventricular neuroepithelium might be closely associated with the pathogenesis of congenital hydrocephalus in HTX rats.

Our report concerns gastric carcinoid tumors in a man and his younger sister who had no endocrine symptoms. The tumors in both cases were multiple, located in the corpus, and showed no significant differences in light microscopic and immunohistochemical examination. In electron microscopic observation, the endocrine granules of tumor cells were roughly classified into four types: granules with fine granular content with low electron density, irregularly striped granules with medium electron density, concentrically laminated or regularly striped granules, or smaller and almost uniformly high electron-dense granules in which it was difficult to recognize the internal structure. From the sequential morphological changes of the granules, we have considered that each type of granule reflects various stages of granulogenesis, although the possibility that they are distinct and contain different hormones or chemical mediators is not absolutely ruled out.

We report one rare case of superficial angiomyxoma of the right inguinal region, in a 67-year-old man. The tumor, measuring 4.5 x 4.0 x 3.0 cm, had a finger-like shape, was composed of a well circumscribed conglomerate of multiple myxomatous nodules and was located partially in the dermis and partially in the subcutaneous tissue. Microscopically, in contrast to previously reported cases, the tumor was composed mainly of oval plump stromal cells with an amphophilic cytoplasm. Spindle-shaped stromal cells were scattered throughout the tumor. The tumor border was not infiltrative and was well defined by thick hyalized collagen bundles. Neither hyperchromasia nor pleomorphism was apparent. No mitotic figures were detected in the specimens prepared. Small to medium-sized blood vessels showed a scattered distribution, but large vessels, seen frequently in aggressive angiomyxoma, were absent. Moreover, no plexiform capillary pattern was evident. These findings were diagnostic of superficial angiomyxoma. Although this disease entity is considered as including cutaneous focal mucinosis, follicular fibroma, trichofolliculoma and trichogenic adnexal tumor, we propose that these tumors should be excluded.

The juxtaglomerular cell tumor (JGCT) of the kidney is a rare neoplasm which commonly secretes renin. This tumor often occurs in teenagers. This paper documents the 14th adult-onset (over 30-years-old) case with a giant JGCT which measured 9.0 x 8.0 x 7.5 cm. Histologically, this tumor was composed of both vascular and tubular components. Immunohistochemically, the vascular component reacted with renin, cytokeratin 7, ulex europaeus agglutinin-1, vascular endothelial growth factor (VEGF) and Flk-1 (VEGF-R2), whereas the tubular component was positive for renin, epithelial membrane antigen (EMA), cytokeratin 7, alpha-1-antitrypsin, VEGF and Flk-1. This finding suggests that both vascular and tubular components of JGCT may promote neoplastic proliferation via an autocrine mechanism through the action of VEGF.

Signet-ring cell carcinoma (SRCC) of the prostate is a very rare neoplasm and there have been only 38 cases reported to date. Here the 39th case of prostatic SRCC containing a small amount of neutral mucin, prostatic specific antigen (PSA) and prostatic specific acid phosphatase (PSAP) in the signet-ring cells is reported. It was also found that some intracytoplasmic lumina were derived from the shallow or deep invagination of luminal membranes of cancer cells that formed the neoplastic glands. Using immunohistochemistry, a combination of monoclonal antibodies against cytokeratins 7 and 20 as well as PSA and PSAP may be useful in differentiating prostatic primary SRCC from metastatic SRCC originating in the gastrointestinal tract.

BACKGROUND In order to elucidate the significance of myofibroblasts in invasive growth of colorectal adenocarcinomas, we examined the number of myofibroblasts at the tumor border of colorectal adenocarcinomas. METHOD A total of 91 invasive colorectal adenocarcinomas were examined immunohistochemically using anti-alpha-smooth muscle actin (ASMA) and high-molecular-weight caldesmon (h-CD) antibodies; 25 carcinomas confined to the submucosa (sm carcinomas), 40 carcinomas confined to the muscularis propria (mp carcinomas) and 26 carcinomas invading the subserosa or adventitia (ss carcinomas). We considered ASMA-positive and h-CD-negative stromal cells as myofibroblasts. RESULTS Twenty-seven (67%) of the 40 mp carcinomas and 25 (96%) of the 26 ss carcinomas had a small number of myofibroblasts at the tumor border facing the muscularis propria. CONCLUSIONS Although direct evidence is lacking, there is a possibility that the further immediately vertical and radial invasion of carcinoma cells into the subserosa or adventitia is associated with a smaller number of myofibroblasts at the tumor border facing the muscularis propria in mp carcinomas, resulting in a low incidence of mp and a high incidence of ss carcinomas in the colorectum.