The purely epithelioid malignant peripheral nerve sheath tumor

The purely epithelioid malignant peripheral nerve sheath tumor (PNST) is a rare form of PNT possibly first described by McCormack et al. in 1954. This tumor type is distinguishable from the glandular PNT and PNT with differentiated neuroepithelium (medulloepithelioma and neuroepithelioma) and differs from the ordinary epithelioid PNT because of the absence of a spindle cell component typical of malignant PNSTs. The two examples of purely epithelioid malignant PNT we describe arose in the popliteal fossa from the sciatic and tibial nerves of men with no definite evidence of von Recklinghausen's neurofibromatosis. Both tumors were partly mucinous, and so closely mimicked carcinoma and a few non-neurogenic myxoid sarcomas histologically that their final classification depended upon proof of a neural origin.     

Expanding the spectrum of malignant change in schwannomas: epithelioid malignant change, epithelioid malignant peripheral nerve sheath tumor, and epithelioid angiosarcoma: a study of 17 cases

Schwannomas (neurilemmomas) rarely undergo malignant change, most often in the form of either malignant peripheral nerve sheath tumor (MPNST) or angiosarcoma. We characterize the clinical features and the histopathologic spectrum of 17 schwannomas with evidence of malignant change. The study group comprised 7 males and 10 females with an age range of 16 to 76 years, (median, 40 yrs). None of the patients had neurofibromatosis. Lesions ranged in size from 0.6 to 10.5 cm (median, 4.0 cm) and arose mainly in the limbs/limb girdles (7 cases) or head and neck region (7 cases). All tumors contained areas of conventional benign schwannoma. Four cases of pure epithelioid malignant peripheral nerve sheath tumor (EMPNST) were identified, three of which showed immunopositivity for S-100 protein. Four angiosarcomas were identified, predominantly epithelioid-type. Ten schwannomas had an appearance that we have designated epithelioid malignant change (EMC) and, in one of these, EMC coexisted with EMPNST. Large epithelioid cells with abundant eosinophilic cytoplasm, vesicular chromatin, and prominent nucleoli (morphologically similar to cells of EMPNST) were distributed throughout the schwannoma--singly, in clusters, and in one case a microscopic nodule of such cells was also present. These large epithelioid cells were strongly positive for S-100 protein. Although follow-up data so far are limited, 1 of 5 patients with EMC in whom meaningful follow up was available developed repeated local recurrence (median follow up, 21 mos), one patient each with EMPNST and angiosarcoma died of local and metastatic disease. Pure EMPNST is rare; however, we confirm the tendency of MPNST to show epithelioid cytomorphology when arising in a benign schwannoma. We also confirm the distinctive (albeit infrequent) tendency of angiosarcoma to arise in schwannomas. We describe EMC in schwannomas and suggest that this represents a putative precursor lesion of EMPNST. At this time, we do not have an explanation for the tendency of schwannomas to show epithelioid cytomorphology when they undergo malignant change.     

Perivascular epithelioid cell tumor ('PEComa') of the uterus: a subset of HMB-45-positive epithelioid mesenchymal neoplasms with an uncertain relationship to pure smooth muscle tumors.

The family of lesions thought to be composed at least in part of perivascular epithelioid cells, characterized as HMB-45-positive epithelioid cells with clear to eosinophilic granular cytoplasm and a propensity for a perivascular distribution, includes some forms of angiomyolipoma and lymphangioleiomyomatosis, as well as clear cell "sugar" tumor (CC-SUGAR). When composed predominantly or exclusively of epithelioid cells, it has been suggested that these lesions be classified as "perivascular epithelioid cell tumors" (PEComa). Four cases of uterine PEComa have been described in the literature, three of which exhibited aggressive behavior. We report the clinical, histologic, and immunohistochemical features of eight more examples of uterine PEComa. Patients ranged in age from 40 to 75 years (mean 54 years). Most patients presented because of abnormal uterine bleeding, and grossly a mass was present in the uterine corpus. Morphologically, the tumors could be divided into two groups (A and B). Group A tumors demonstrated a tongue-like growth pattern similar to that seen in low-grade endometrial stromal sarcoma and were composed of cells that tended to have abundant clear to eosinophilic pale granular cytoplasm, diffuse HMB-45 expression, and focal muscle marker expression. Group B tumors were composed of epithelioid cells with less prominent clear cell features, smaller numbers of which were HMB-45-positive. They also featured extensive muscle marker expression and a lesser degree of the endometrial stromal sarcoma growth pattern seen in group A tumors. Two of the four patients with group B tumors had pelvic lymph nodes involved by lymphangioleiomyomatosis, and one of these patients had the tuberous sclerosis complex. Seven of the eight patients with PEComas were treated by hysterectomy. All eight patients are alive and well, although follow-up of >2 years was available only for two patients. Uterine epithelioid smooth muscle tumors and low-grade endometrial stromal sarcomas were compared with the PEComas. Group A PEComas, group B PEComas, and epithelioid smooth muscle tumors were all parts of a continuous histologic spectrum, with group A PEComa at one end of the spectrum and epithelioid smooth muscle tumors at the other, while group B tumors shared features of both. PEComa was histologically and immunohistochemically distinct from endometrial stromal sarcoma. Our data and a review of the literature indicate that PEComa is a subset of HMB-45-positive epithelioid mesenchymal tumors of the uterus with an uncertain relationship to pure smooth muscle tumors. Although none of the patients in this study experienced recurrence during a short follow-up period, some reported in the literature have had recurrences; consequently, we think uterine PEComa should be considered a tumor of uncertain malignant potential until long-term outcome data for a larger number of patients become available.     

Ovarian clear cell carcinoma with papillary features: a potential mimic of serous tumor of low malignant potential

The differential diagnostic problems usually associated with clear cell carcinoma (CCC) of the ovary have been well characterized and include primitive germ cell tumor, sex cord stromal tumor, and metastasis. Distinction from other types of surface epithelial carcinoma may also pose a diagnostic challenge, but the potential for misdiagnosis of serous tumor of low malignant potential (S-LMP) is not well recognized. We report 13 cases of ovarian CCC with prominent papillary architecture that were initially misdiagnosed as S-LMP or low-grade serous carcinoma either on frozen section or at final diagnosis. The ages of the patients ranged from 39 to 65 years (mean, 52.2 y). All patients presented with a pelvic mass; 1 was undergoing evaluation for infertility. Macroscopically, most were described as unilateral, multilocular cysts with internal papillary structures. On microscopic examination, each tumor had a papillary architecture that accounted for 30% to 95% of the tumor; in 6 cases, the cores of the papillae were hyalinized. The neoplastic cells covering the papillae had clear to granular and eosinophilic cytoplasm. Hobnail cells were focal and often subtle. Most had a low mitotic index (9/13) and/or deceptively bland cytology (8/13); only careful attention to the cytologic features and/or mitotic index allowed correct identification of the tumor type in 5 cases. Six were associated with pelvic/ovarian endometriosis. Ten were Federation of Gynecology and Obstetrics stage I (8 IA, 2 IC), 2 were stage II (1 IIB, 1 IIC), and 1 stage IIIC. CCC with prominent papillary architecture is uncommon, but may pose a challenging differential diagnosis with S-LMP, resulting in inadequate staging and delayed treatment. Features most helpful in distinguishing papillary CCC are unilaterality, nonhierarchical branching, monomorphous cell population, and the presence of more typical CCC patterns elsewhere in the tumor. The presence of endometriosis, although not specific, should also prompt consideration for papillary CCC. Increased numbers of mitotic figures may not be present and high-grade cytologic atypia may be focal, requiring careful examination of multiple tumor sections for detection. As CCC and S-LMP exhibit significantly different immunoreactivity for Wilms' Tumor 1 and estrogen receptor, these markers may also be useful adjunctive tests in problematic cases.     

Epithelial ovarian tumours of low malignant potential

The available literature and the management of epithelial tumours of low malignant potential (LMP) is reviewed. The criteria for a diagnosis of LMP at the University of the Witwatersrand are delineated in detail. Based on the records in the Ovarian Tumour Registry of this University, experience with 29 such tumours over 4 years is presented. Of these, 14 (48.3%) were of the serous variety, 12 were mucinous (41.4%), and 2 (6.9%) were mucinous-serous, the remaining 1 (3.4%) being endometrioid. LMP tumours accounted for 12.9% of proliferating epithelial ovarian tumours in black patients compared with 16.9% in white patients. Pelviperitoneal cytological washings for detection of malignant cells in patients with LMP tumours is mandatory.     

Diagnosis of smooth muscle tumor of the small bowel

In this report, the experience in the diagnosis of smooth muscle tumor of the small bowel in 32 cases (14 leiomyomas and 18 leiomyosarcomas) was presented. The authors discussed the clinical features, the pathological classification of the tumor, the diagnosis of intestino-intestinal fistula, and ways to improve its preoperative diagnosis.     

The action potential of guinea pig bladder smooth muscle

The smooth muscle of the guinea pig bladder demonstrates in vitro spontaneous electrical activity in the form of action potentials which are associated with contraction. The action potential frequency is highly voltage-sensitive. The relative contributions of Na, Ca and K to the action potential elicited by depolarizing current have been studied using intracellular microelectrodes. In solutions in which NaCl is replaced by sucrose, the membrane hyperpolarizes and the rate of rise and after-hyperpolarization of the elicited action potential is increased. The amplitude is unaffected. In Ca-deficient solutions, the membrane depolarizes, the rate of rise and amplitude of the action potential is reduced, and the after-hyperpolarization is decreased. Nifedipine reduces amplitude and rate of rise but does not affect after-hyperpolarization. In the presence of the K-channel antagonist TEA, the duration of the action potential is prolonged, but the amplitude and rate of rise are unaffected. After-hyperpolarization is not reduced. It is concluded that the action potential of guinea pig bladder muscle, like many other smooth muscles studied, is Ca-based. Repolarization depends on changes in K conductance. The after-hyperpolarization is voltage-sensitive.     

Renal smooth muscle tumor with features of lymphangioleiomyomatosis. Problems in histological diagnosis

A 44-year-old woman with left kidney tumor involving the perirenal and retroperitoneal lymph nodes is presented. Imaging findings including ultrasonography and computerized tomography showed renal and para-aortic masses and no features of lymphangioleiomyomatosis or angiomyolipoma were seen. The histopathological examination was considered as a renal smooth muscle tumor with features of lymphangioleiomyomatosis. Diagnosis considerations, particularly histopathological, immunohistochemical and hormonal studies are discussed and we comment the distinction of this case from the benign mesenchymal tumors.     

Pigmented epithelioid melanocytoma: a low-grade melanocytic tumor with metastatic potential indistinguishable from animal-type melanoma and epithelioid blue nevus

In the course of a study of borderline melanocytic tumors, we observed a distinctive group of lesions characterized by features very similar to those previously described in the literature as "animal-type melanoma" and epithelioid blue nevus of Carney complex. We have designated these lesions as pigmented epithelioid melanocytoma (PEM). Herein, we present a clinical-pathologic analysis of 41 consecutive PEM from 40 patients and compare them with 11 epithelioid blue nevi from patients with Carney complex. PEM occurred in both sexes of different ethnic backgrounds, including white, Hispanic, black, Asian, and Persian. The median age of occurrence was 27 years (range 0.6-78 years). Tumors had wide distribution with extremities being the most common site. The tumors were formed by deep dermal (mean Breslow's thickness 3.3 mm) proliferation of heavily pigmented epithelioid and/or spindled melanocytes. Five lesions were part of combined nevus. Ulceration was present in 7 cases. Tumor necrosis was present in 1 case. Regional lymph nodes were sampled in 24 cases (59%). In 11 cases, lymph nodes contained metastases (46%). Liver metastases occurred in 1 case. None of the patients died of disease. Clinical follow-up of more than a year (mean 32 months, range up to 67 months) was available in 27 cases (67%). We found no histologic criteria separating metastasizing and nonmetastasizing PEM. Ulceration was the only feature more common in PEM than epithelioid blue nevi of Carney complex. Otherwise, they were histologically indistinguishable. Our data show that PEM is a unique low-grade variant of melanoma with frequent lymph node metastases but indolent clinical course. We suggest that PEM be considered as a provisional histologic entity encompassing both animal-type melanoma and epithelioid blue nevus.     

Testicular papillary cystadenomatous tumor of low malignant potential: a case report and discussion of the literature

We report the fifth case of a rare testicular serous papillary cystadenomatous tumor of low malignant potential. All patients presented with a testicular mass. Histologically, the tumor can be differentiated from testicular papillary cystadenocarcinoma. The natural history of this rare tumor is yet to be determined.     

胃平滑肌肿瘤的诊断和外科治疗

目的 探讨胃平滑肌肿瘤的诊断及治疗方法。方法 对34例经手术治疗的胃平滑肌肿瘤的临床资料进行回顾性分析。结果 胃平滑肌肉瘤肿块较大，本组中最大直径≥5cm者占68％，≥10cm者占50％；胃平滑肌肉瘤大多位于胃底体区，占94％；胃平滑肌肉瘤有三大临床表现：上腹痛、上腹包块、出血。胃镜、钡剂X线透视、CT有助于诊断。随访结果：本组3、5、10年生存率分别是87％、52％及26％。结论 对胃平滑肌肉瘤应积极考虑手术治疗。根据肿块大小、部位和浸润程度决定手术方式。     

Primary smooth muscle tumor of the liver encasing hepatobiliary cystadenoma without mesenchymal stroma.

We describe a 59-year-old Japanese woman with a large mass of her liver encasing cystic components. Radiologic imaging showed the mass to be hypervascular, and surgical resection disclosed a white tumor. The solid portion was immunohistochemically characterized as a smooth muscle tumor. The cystic components were multilocular and lined with columnar epithelium, consistent with a hepatobiliary cystadenoma. The epithelium strongly stained for CA19-9. The subepithelial space was occupied by collagenous connective tissue interspersed with a small number of spindle-shaped cells. The cystic lesions lacked the mesenchymal stroma between the epithelium and connective tissue layer. There have been no previous reports of a hepatic smooth muscle tumor encasing a hepatobiliary cystadenoma. Because of the pathogenesis of the cystadenoma, it is possible to assume that the smooth muscle tumor also arose from the cells composing the biliary duct in association with the development of the cystadenoma.     

HMB-45/melan-A and smooth muscle actin-positive clear-cell epithelioid tumor arising in the ligamentum teres hepatis: additional example of clear cell 'sugar' tumors

HMB-45-positive clear-cell epithelioid tumor arising in the ligamentum teres hepatis of a 13-year-old Japanese girl is described. The well-defined tumor was completely removed and measured 9 x 7 x 6 cm. Cut sections showed a tan-white, homogeneous appearances with no hemorrhage or necrosis. The tumor was composed of nests or sheets of polygonal or oval-shaped cells rich in clear or finely granular cytoplasm. Capillary network was well developed, and sinusoid vessels were often seen with occasional perivascular hyalinization. There was moderate nuclear atypia but mitotic figures were absent. Periodic acid-Schiff stain showed a large amount of glycogen digested by diastase. Immunohistochemical stains for smooth muscle actin, Melan-A, and HMB-45 were positive in most of the tumor cells. Stains for vimentin, muscle actin, and HAM56 were focally positive, whereas stains for desmin, cytokeratin, epithelial membrane antigen, S-100, CD34, CD68, CD99, neurofilament proteins, and estrogen/progesterone receptors were negative. Ultrastructurally, the cytoplasm contained a considerable number of mitochondria, monoparticipate or membrane-bound glycogen, and longitudinally oriented thin filaments with focal condensations and subplasmalemmal densities. The histopathology of the present case, originally interpreted as epithelioid leiomyoma, was consistent with clear cell "sugar" tumors. The present case may indicate ubiquitous distribution of clear cell "sugar tumors" of which histogenesis remains unknown but is presumed to be of perivascular epithelioid cell origin.     

胃平滑肌肿瘤的临床与病理分析

目的探讨胃平滑肌肿瘤的诊断、病理学特点和治疗选择 .方法对 1984年 2月至 1999年 2月经治的 45例胃平滑肌肿瘤进行回顾性分析 .结果术前确诊仅 15例 ( 33 3% ) . 45例均予手术治疗并经病理学证实 .随访中 3例因肿瘤广泛扩散而衰竭死亡 . 2例出现复发而予再次手术 ,再次手术后已分别存活 2年、 3年;其余病例随访恢复良好 .结论确立本病的诊断要根据病史、多种特殊检查的结果、肿瘤的大体形态和术中、术后病理等综合分析 .手术切除为其首选治疗方法 ,在术式选择上应根据肿瘤的部位、大小和生物学行为而定 ,一般无需行广泛的根治性胃切除 .良、恶性平滑肌肿瘤均应强调术后长期随访 ,以提高生存率 .