Anterior mediastinal neuroblastoma in an adult: an additional case of a rare tumor in an unusual location with review of the literature

Neuroblastoma is rare in the adult population, especially in thoracic or mediastinal locations, with only 25 previously reported cases. We report an additional example of primary thymic neuroblastoma in a previously asymptomatic 71-year-old man with an anterior mediastinal mass who underwent robotic excision with pericardium and adjacent lung. The tumor was a 5.2 cm partially encapsulated, white-tan and rubbery mass with grossly identifiable areas of necrosis (25%) and hemorrhage. Histologically, the specimen showed a rim of adipose tissue and residual thymic tissue with areas of cystic thymic epithelium and prominent lymphoid tissue containing Hassall's corpuscles. The tumor was composed of uniform, round cells with scant cytoplasm and small nuclei with inconspicuous nucleoli set within a background of conspicuous neuropil. Mitotic figures were easily found. By immunohistochemistry, the tumor cells expressed synaptophysin, chromogranin, NKX2.2 (diffuse, nuclear), GFAP (patchy), SMI31 (neurofilament) (focal, cytoplasmic), and TdT (diffuse, nuclear), while lacking expression of CD99, TTF-1, CK 20, MCPyV, PHOX2B, Olig2, OCT3/4, CD45, CD3 and PAX5. S100 protein was negative in the neuroblastic cells, with scattered positive cells in a vague sustentacular-like pattern. Fluorescence in situ hybridization for isochromosome 12p and EWSR1 gene rearrangement were negative. As thymic neuroblastoma is extremely rare in adults, a neuroblastic tumor of germ cell origin (either primary or metastatic) or spread from a sinonasal tract tumor should be excluded because of differing treatments and prognoses. The properties of these rare neoplasms appear similar to olfactory neuroblastoma rather than pediatric-type neuroblastoma.

Primary mediastinal seminoma with florid follicular lymphoid hyperplasia: a case report and review of the literature

BACKGROUND

First described in 1955 Primary mediastinal seminomas are rare. Only 1-4% of mediastinal tumours are germ cell tumors; majority of which are teratomas. They typically present in men aged between 20 and 40 years. Very few cases are reported in the literature. Florid follicular lymphoid hyperplasia can obscure the malignant cells and is a rarer finding still. We present a rare case of a 48 year old man with a primary mediastinal seminoma with florid follicular lymphoid hyperplasia; found following excision of a clinically presumed thymoma.

CASE PRESENTATION

A 48 year old man was referred for excision of a thymic mass. The presumed diagnosis was a thymoma; following preoperative investigations. The mass was incidentally found on a radiological imaging. However, the patient did report mid-sternal discomfort on lying flat and breathlessness. The patient underwent a thymectomy via a partial median sternotomy with good recovery. Histological assessment was that the mass was in fact a primary mediastinal seminoma with florid follicular lymphoid hyperplasia. A primary testicular malignancy was excluded and the patient required no further oncological treatment.

CONCLUSIONS

Only 11 cases have previously been reported of primary mediastinal seminoma with florid follicular lymphoid hyperplasia. Although rare, a primary mediastinal seminoma should be considered as a differential diagnosis for presentations with a thymic mass. Tumour markers can be helpful, however are only positive in third of cases. Ultrasound imaging of the gonads is essential to exclude a primary gonadal lesion. Pure seminomas are radiotherapy and chemotherapy sensitive however the mainstay treatment of primary mediastinal seminomas remains surgical excision. Radiotherapy is reserved postoperatively for incomplete surgical margins.

Extragonadal malignant germ cell tumors: a clinicopathological and immunohistochemical analysis of 48 cases at a single Chinese institution

Primary extragonadal malignant germ cell tumors (EMGCTs) are rare and characterized by the location in the midline of the body, including mediastinum, CNS, retroperitoneum and coccyx. EMGCTs present with different clinical and biologic characteristics in different tumor locations. Accurately diagnosing MEGCTs would be very difficult by performing on HE staining alone, and requires immunohistochemical verification. This study was to investigate the biological feature of EMGCTs and diagnostic value of immunohistochemical markers OCT3/4, CD117, PLAP, AFP, β-HCG and CD30 in EMGCTs. A retrospective study was performed on 48 patients with EMGCTs. EMGCTs were found to occur predominantly in males, especially for mediastinal MGCTs. The tumor locations included mediastinum, CNS and retroperitoneum. The mediastinum and CNS were the most common sites of EMGCTs. Seminoma/germinomas (64.6%) was the most common histological subtypes of EMGCTs. Chest pain, dyspnea, cough and fever were the most common clinical presentations in mediastinal MGCTs. Headache, visual disturbances, endocrine abnormalities, and signs of increased intracranial pressure were common clinical symptoms in CNS MGCTs. Abdominal mass with or without pain, backache and weight loss were common clinical presentations in retroperitoneal MGCTs. PLAP, CD117 and OCT3/4 were highly expressed in seminomas/gernimomas. CD30, EMA and CK AE1/3 staining were positive in embryonal carcinoma. AFP and β-HCG positive staining are characteristic in yolk sac tumors and choriocarcinoma, respectively. Patients with seminomas/germinomas had a better prognosis than those with NS/G-GCTs. Our finding suggests that the accurate diagnosis of EMGCTs is critical not only for predicting the tumor progression but also for patient management. Immunohistochemical markers have become an important tool in the diagnosis and differential diagnosis of EMGCTs.

A case report of sclerosing thymoma of the anterior mediastinum: an exceedingly rare morphology

The morphology of thymoma is diverse, although 5 basic subtypes are recognized in the World Health Organization classification system. Sclerosing thymoma was first documented in 1994 and to date only 13 cases have been reported. Sclerosis itself is considered to be an ancient change and can occur in various histological subtypes. Herein, we present a case of a 62-year-old woman incidentally found to have an anterior mediastinal mass, 31 × 24 × 17 mm in size, without an associated autoimmune disease such as myasthenia gravis. The mass was finally diagnosed as sclerosing thymoma derived from type A thymoma. Intraoperative pathological examination using a limited amount of sample did not allow a definitive diagnosis of thymoma in this case. When dealing with fibrous lesions observed in limited samples such as biopsy and intraoperative frozen specimens, recognizing sclerosing thymoma is important since there are several disease entities accompanying fibrosis in the anterior mediastinum.

Mediastinal Yolk Sac Tumor Producing Protein Induced by Vitamin K Absence or Antagonist-II

Extragonadal yolk sac tumors (YSTs) are rare. We herein report the case of a 66-year-old man with mediastinal, lung and liver tumors. The largest mass was located in the liver and contained a high concentration of protein induced by vitamin K absence or antagonist-II (PIVKA-II) and alpha-fetoprotein. Therefore, the lesion was difficult to distinguish from hepatocellular carcinoma. Finally, YST was diagnosed based on the results of a liver biopsy. Although chemotherapy was effective, the patient died of respiratory failure. The autopsy revealed primary mediastinal YST. In the current report, we describe this case of PIVKA-II-producing YST and review previous cases of PIVKA-II-producing tumors other than hepatoma.

The histogenic origin of melanoma arising in respiratory epithelium of a teratomatous germ cell tumor of the mediastinum: an enigma unraveled from an unlikely source

Mixed germ cell tumors are rare neoplasms that are known to occur in the anterior mediastinum. Characterized by two or more types of germ cell components, these tumors comprise upwards of 25% of mediastinal germ cell tumors. Even rarer are those harboring somatic-type malignancies such as carcinoma, sarcoma, and hematopoietic malignancies. To date, however, there are no known cases of melanoma arising in a malignant mixed germ cell tumor of the anterior mediastinum. We describe the first case of malignant melanoma with spindle and epithelioid components arising from respiratory epithelium in a mediastinal malignant mixed germ cell tumor of a 32-year-old male. In addition, we also provide evidence supporting the theory of neuroendocrine cells as the origin of melanoma arising in the respiratory epithelium. This case emphasizes the need to carefully evaluate all germ cell tumors, not only for a myriad of benign embryological components, but also for malignancies arising in these components, as they might change the prognosis and patient's course of treatment. This microscopic approach should bring to light the diversity of mixed germ cell tumors in addition to somatic malignancies with corresponding biologic potentials.

Pathobiology of Primary Mediastinal B-Cell Lymphoma

Controversy still exists over the response to therapy and prognosis of patients with primary mediastinal B-cell lymphoma (PMBL). Recent data from the International Extranodal Lymphoma Study Group (IELSG) suggest that a MACOP-B (methotrexate, adriamycin, cyclophosphamide, vincristine, prednisone, bleomycin) chemotherapy regimen followed by radiotherapy may be a better induction strategy than other previously used treatments. Although the pathobiology of PMBL has been widely studied, its precise histology, phenotype, and molecular characteristics are still not clear. To date, phenotypic analysis has revealed the following phenotype: positivity for CD45 and CD20, but negativity for CD3, CD10, CD21, Class I/II major histocompatibility antigens, and a variety of other immunohistochemical markers. CD79a is generally detected, despite an absence of surface immunoglobulins (Igs). CD30 staining is observed in most cases, but is weaker and less homogeneous than in classic Hodgkin's lymphoma or anaplastic large cell lymphoma. BCL-2 protein is usually expressed but there are few data describing the expression of MUM1/IRF4, PAX5/BSAP, BCL-6, or the B-cell transcription factors BOB.1, Oct-2, and PU.1. Cytogenetic studies reveal gains in segments of chromosome 9p, including amplification of the REL proto-oncogene and the tyrosine kinase gene JAK2. Other molecular findings include: C-myc mutations or rearrangements, p53 mutations, IgV(H), gene mutations, and bcl-2 and mal over-expression. bcl-6 mutations and bcl-2 gene rearrangements are generally absent, suggesting that PMBL is of pre-germinal center (GC) origin. However, two recent reports show isotype-switched Ig genes with a high frequency of somatic hypermutations as well as variants in the 5' noncoding region of the bcl-6 gene. The IELSG collected 137 PMBL cases for extensive pathologic review. Histologically, the lymphomatous growth was predominantly diffuse with sclerosis that induced compartmentalized cell aggregation. It consisted of large cells with varying degrees of nuclear polymorphism and clear to basophilic cytoplasm. Molecular analysis was performed on 40 cases and showed novel findings. More than half of the cases displayed bcl-6 gene mutations, which usually occurred together with functioning somatic IgV(H) gene mutations, and BCL-6 and/or MUM1/IRF4 expression. The present study supports the concept that PBML is derived from activated GC or post-germinal center cells. However, it differs from other aggressive B-cell lymphomas in that it shows defective Ig production despite the expression of Oct-2, BOB.1, and PU.1 transcription factors, and a lack of IgV(H) gene crippling mutations.

Mucinous adenocarcinomas of the thymus: report of 2 cases and review of the literature

BACKGROUND

Most adenocarcinomas of the mediastinum are metastatic lesions. Primary thymic adenocarcinomas are extremely rare neoplasms. We could find only 12 cases reported in the literature; of these 12, only 4 were of the mucinous subtype.

DESIGN

We report 2 additional cases of the mucinous subtype, including a previously unreported mucinous variant with numerous psammoma bodies.

RESULTS

The first case in a 61-year-old woman resembled a mucinous (colloid) carcinoma of other organs such as the breast and colon. It consisted of islands and strips of tumor cells floating in large pools of extracellular mucin. A unique feature of this tumor was the presence of numerous psammoma bodies. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) 7 and negative for CD5. The second case in an 82-year-old woman was a mucinous adenocarcinoma arising from a thymic cyst with areas of transition from benign to dysplastic epithelium. The tumor cells formed dilated glands, cords, and small nests that infiltrated the thymic cyst wall and exhibited evidence of mucin production. Immunohistochemically, the tumor cells were positive for CK 7 and focally positive for both CD5 and CK 5/6.

CONCLUSIONS

Mucinous adenocarcinoma, with or without, psammoma bodies, may be of primary thymic origin and should be considered in the differential diagnosis of malignant mediastinal tumors. These 2 cases provide further documentation of the rare occurrence of primary mucinous adenocarcinomas of the thymic gland.

Germ Cell Tumors With Sarcomatous Components

The clinicopathologic features of 46 patients with germ cell tumors with sarcomatous components (GCTSC) involving either the primary site or their metastases were studied. There were 43 men and 3 women aged 17 to 74 years. Twenty-three tumors arose in the mediastinum, 2 in the retroperitoneum, and 21 in the gonads. The germ cell component consisted of pure mature or immature teratoma (23 cases), teratoma mixed with other seminomatous or nonseminomatous components (17), pure seminoma (2), intratubular germ cell neoplasia (1), and yolk sac tumor (1). The SC included embryonal rhabdomyosarcoma (29), angiosarcoma (6), leiomyosarcoma (4), undifferentiated sarcoma (3), myxoid liposarcoma (1), malignant peripheral nerve sheath tumor (1), malignant "triton" tumor (1), and epithelioid hemangioendothelioma (1). Immunohistochemical studies were carried out in 34 cases with appropriate results supporting the diagnoses. Metastases containing both GCT and SC were observed in 6 cases, metastases of SC alone in 4, and metastases containing only GCT elements in 3. All patients were treated by cisplatinum-based chemotherapy plus other agents followed by surgery. Clinical follow-up was available in 40 patients (1 to 96 mo; mean=24 mo). Thirty-two of 40 patients either died of tumor (25/40; 62.5%) or were alive with advanced, progressive disease (7/40; 17.5%), and only 8/40 (20%) were alive and free of disease between 5 to 40 months (mean=18 mo). Comparison of these patients with an age-matched and stage-matched control group of patients with GCT without SC showed statistically significant differences in survival between the 2 cohorts (P <or=0.001). On the basis of our findings, the presence of SC appears to represent a poor prognostic sign for GCTs of gonadal and extragonadal origin.

Mediastinal follicular dendritic cell sarcoma involving bone marrow: a case report and review of the literature

We report a rare case of mediastinal follicular dendritic cell (FDC) sarcoma involving the bone marrow. The patient, a 46-year-old woman, had a clinically aggressive tumor in the anterior mediastinum that was initially diagnosed as a diffuse B-cell lymphoma. She received chemotherapy but showed no significant improvement. One year later, the patient presented at our institution with pelvic bone metastases. Biopsy specimens of the sacrum lesion and bone marrow were obtained. The diagnosis of FDC sarcoma was made based on histological examination and immunohistochemical findings, including strong positive staining of tumor cells for CD21, CD23, clusterin, and epidermal growth factor receptor (EGFR) and negative staining for CD20, CD30, CD45, CD1a, S-100, vimentin, and keratin cocktail. Histological examination and immunohistochemical studies of a previous biopsy of the mediastinal mass confirmed the diagnosis of mediastinal FDC sarcoma. The patient was treated with an appropriate chemotherapy regimen; 1 month later, follow-up bone marrow biopsy revealed no tumor cells. Although FDC sarcoma is considered a low-grade tumor, the tumor in the present case not only developed at an unusual location with bone metastasis but also involved bone marrow. To our knowledge, this is the first such case ever reported. This case also highlights the utility of EGFR as an immunohistochemical marker of dendritic cell tumors that could be used as a diagnostic tool and guide for choosing appropriate chemotherapy regimens.

Mediastinal lymphangiomatosis coexisting with occult thymic carcinoma

Mediastinal lymphangiomatosis in a 70-year-old woman was diagnosed on a medical checkup. The tumor was resistant to sclerotherapy with OK432 or bleomycin. The patient continued on a downhill course and died approximately 3 years after the initial diagnosis. Autopsy revealed a large tumor mass occupying the anterior mediastinum and firmly adhered to the pericardium and the pleura. The tumor consisted of two intermingled lesions: dilated vessels lined with D2-40-positive lymphatic endothelium and CD5-positive atypical cell nests with focal keratinization. The former was diagnosed as lymphangiomatosis and the latter as thymic squamous cell carcinoma. Vascular endothelial growth factor (VEGF)-C, a growth factor for lymphatic endothelial cells, was expressed by the carcinoma, and VEGF-C receptor was expressed by the endothelium of lymphangiomatosis. These findings suggested that VEGF-C derived from the thymic carcinoma induced the lymphangiomatosis lesion in a paracrine manner.

Cystic well-differentiated neuroendocrine carcinoma (carcinoid tumor): a clinicopathologic and immunohistochemical study of two cases

Two cases of primary neuroendocrine carcinoma (carcinoid tumor) arising in the walls of a multilocular thymic cyst (MTC) are described. The patients were 2 men, ages 36 and 44 years. Clinically, the patients had chest pain, cough, and dyspnea. Radiographic evaluation demonstrated the presence of anterior mediastinal tumor in both patients, and complete surgical resection of the tumor mass was performed. The tumors measured approximately 6 and 8 cm in greatest dimension and were cystic with solid areas but did not show areas of necrosis or hemorrhage. Histologic examination revealed a cystic tumor with features similar to those previously described for MTCs. In addition, in the walls of the cystic structures, there was cellular proliferation arranged in a nesting growth pattern, similar to the more solid areas of the tumor. The tumor was characterized by a homogenous cellular proliferation with mild cellular atypia and no more than 2 mitotic figures per 10 high-power fields. Immunohistochemically, the tumor cells showed strong positive reactions for keratin and neuroendocrine markers, ie, chromogranin and synaptophysin. Both patients were alive after periods of 12 and 18 months.

Mediastinal rhabdomyoma: case report and review of the literature

Rhabdomyomas are benign tumors in which at least some cells are differentiated as skeletal muscle cells with cytoplasmic cross-striations. Extracardiac adult rhabdomyoma is an extremely uncommon benign neoplasm that usually involves the head and neck region. Rare cases have been reported to involve other sites of the body including mediastinum. We report the fourth case of mediastinal adult rhabdomyoma.

Primary parathyroid tumors of the mediastinum: a clinicopathologic and immunohistochemical study of 17 cases

We describe 17 cases (9 women, 8 men; aged 36 to 72 years) of primary parathyroid tumors occurring primarily in the anterior mediastinum. Clinically and radiologically, all patients had an anterior mediastinal tumor. All patients had metabolic disturbances with calcium and phosphorus. Of 17 patients, 13 had clinical primary hyperparathyroidism, 1 had secondary hyperparathyroidism due to polycystic kidney disease, and 1 had a history of prostatic carcinoma and 1 of chronic obstructive pulmonary disease. In 1 patient, the tumor was found at autopsy. Grossly, the tumors varied in size from 2 to 7 cm in greatest dimension. Histologically, 2 tumors showed features of parathyroid carcinoma, and 15 tumors showed more conventional features of parathyroid adenomas. Six tumors were predominantly oncocytic, 6 were composed predominantly of chief cells, and 3 had mixed cellular composition. Immunohistochemical studies for chromogranin, synaptophysin, low-molecular-weight keratin (CAM 5.2), and parathyroid hormone were performed in 10 cases (8 parathyroid adenomas and 2 parathyroid carcinomas). All the tumors examined showed variable positive reaction for those antibodies. The cases highlight the importance of keeping primary parathyroid tumors in the differential diagnosis of anterior mediastinal tumors.

Expression pattern of intracellular leukocyte-associated proteins in primary mediastinal B cell lymphoma

Two microarray studies of mediastinal B cell lymphoma have shown that this disease has a distinct gene expression profile, and also that this is closest to the pattern seen in classical Hodgkin's disease. We reported previously an immunohistologic study in which the loss of intracellular B cell-associated signaling molecules in Reed-Sternberg cells was demonstrated, and in this study we have investigated the expression of the same components in more than 60 mediastinal B cell lymphomas. We report that these signaling molecules are frequently present, and in particular that Syk, BLNK and PLC-gamma2 (absent from Reed-Sternberg cells) are present in the majority of mediastinal B cell lymphomas. The overall pattern of B cell signaling molecules in this disease is therefore closer to that of diffuse large B cell lymphoma than to Hodgkin's disease, and is consistent with a common cell of origin as an explanation of the similar gene expression profiles.

Primary Synovial Sarcomas of the Mediastinum

A series of 15 cases of primary mediastinal neoplasms displaying histopathologic, immunohistochemical, and ultrastructural features of synovial sarcoma is presented. The patients' ages ranged from 3 to 83 years, with a male-to-female ratio of 2:1. Nine cases presented as anterior mediastinal masses with chest pain, shortness of breath, and pleural effusion, and 6 cases were in paravertebral location in the posterior mediastinum and presented with neck or back pain and pleural effusion. The tumors measured from 5 to 20 cm in greatest diameter and showed a tan white, soft to rubbery cut surface with areas of hemorrhage and necrosis and foci of gelatinous material. Four cases showed areas of cystic degeneration. In 7 cases, the tumors were well circumscribed; in 6 cases, the tumors grossly invaded the pleura, pericardium, heart, great vessels, chest wall, rib, and vertebra. Histologically, 5 cases displayed a biphasic growth pattern, with well-formed glandular elements admixed with a monotonous spindle cell population. Ten cases were exclusively composed of a monotonous atypical spindle cell proliferation. Immunohistochemical studies showed focal positivity of the tumor cells for cytokeratin and/or epithelial membrane antigen, and strong positivity for vimentin and bcl-2 in the spindle cells in all cases studied (10 of 10). Eight cases also showed focal positivity for CD99. Electron microscopic examination in 5 cases showed oval to spindle tumor cells with closely apposed cell membranes, abundant cytoplasmic intermediate filaments and rough endoplasmic reticulum, and immature desmosome-type cell junctions. Ten patients were treated by complete surgical excision and two by partial excision followed by radiation therapy. In 4 patients, the tumors were inoperable and treated with radiation therapy only. Clinical follow-up was available in 5 patients and showed local recurrence with metastases to lung, lymph nodes, and epidural space from 1 to 3 years in 4 cases and liver metastases and death due to tumor after 6 month in 1 case. Synovial sarcoma should be considered in the differential diagnosis of biphasic and monophasic spindle cell neoplasms of the mediastinum.

Low-Grade Serous Carcinoma of the Ovary Metastatic to the Anterior Mediastinum Simulating Multilocular Thymic Cysts

Three cases of serous borderline tumors of the ovary with areas of serous low-grade carcinoma metastatic to the anterior mediastinum simulating multilocular thymic cysts are presented. The patients are women between the ages of 33 and 50 years. The 3 women had a prior history of primary ovarian neoplasms diagnosed over a period ranging from 3 to 20 years; the 3 patients were in stages IIIA, IIIB, and III. Follow-up radiologic examination revealed the presence of an anterior mediastinal tumor. The 3 patients underwent surgical resection of the mediastinal tumor. Grossly, the mediastinal tumors measured from 7 to 9 cm in greatest diameter and were described as cystic with solid areas. Focal areas of hemorrhage were present, but frank necrosis was not identified. Histologically, all the tumors basically showed similar histopathologic features, namely, those described in multilocular thymic cysts, ie, cystic structures lined by either squamous or low cuboidal epithelium, lymphoid hyperplasia, cholesterol cleft granulomas, and remnants of thymic tissue. In addition, within the cystic structures, there was a neoplastic cellular proliferation with papillary architecture, nuclear atypia, and scattered mitotic figures. Immunohistochemical studies for keratin, MOC31, and CA-125 showed positive staining in tumor cells while placental-like alkaline phosphatase was negative. Two patients remain alive and well after follow-up ranging from 6 to 18 months and 1 patient died of tumor 18 years after initial diagnosis.

Adenocarcinoma of the thymus: mucinous subtype

Primary thymic adenocarcinoma, mucinous subtype, is extremely rare with only one case reported to date. We describe herein a case of thymic mucinous adenocarcinoma. A 59-year-old man was identified to have an anterior mediastinal tumor and was diagnosed as mucinous adenocarcinoma. Clinical and radiographic examinations disclosed no evidence of tumor elsewhere. The patient received radiotherapy, but the general condition deteriorated and died 11 months after tumor detection. Thoracic autopsy revealed an anterior mediastinal tumor measuring greater than 10 cm, uncapsulated, and white. The tumor had clear margins and was clearly isolated from the lung. Histologically, the tumor demonstrated papillary, acinar, and cribriform structure and produced abundant extracellular mucin. Immunohistochemically, most tumor cells were positive for cytokeratin 7, were partially positive for CD5, and were negative for TTF-1, Sp-A, CDX-2, MUC2, napsin A, and cytokeratin 20. Collectively, the diagnosis of the tumor was primary mucinous adenocarcinoma of the thymus. We propose that the mucinous subtype should be recognized as one of the histopathological entities of thymic adenocarcinoma.

Sarcoma of follicular dendritic cells in the dorsal mediastinum

Follicular dendritic cell sarcomas (FDCSs) are very rare and usually originate in lymph nodes. We report an exceedingly rare case with localization in the dorsal mediastinum and, for the first time, provide positron emission tomography (PET) data for this tumor. This report describes the case of a 76-year-old man with a clinically aggressive tumor in the dorsal mediastinum. Computed tomography scan revealed displacement of soft tissue and lymph nodes. PET showed that the tumor had a high proliferation rate. Investigation of the successfully removed tumor mass revealed reactivity of the tumor cells for follicular dendritic cell markers and desmosomes linking adjacent tumor cells at the ultrastructural level. Marked atypia, a high mitotic rate, and areas of coagulative necrosis were found. The tumor in our case revealed the typical features and thus was classified as FDCS. In contrast to previous reports in the literature, preoperative imaging, histology, and immunohistochemistry studies indicated at least an intermediate degree of malignancy. Nevertheless, the patient made a good postoperative recovery and remained apparently disease-free 2 years later.

Malignant peripheral nerve sheath tumor of small round cell type with pleomorphic spindle cell sarcomatous areas

An unusual case of malignant peripheral nerve sheath tumor (MPNST) arising in the posterior mediastinum of a 59-year-old man is reported. Histopathologically, the tumor showed an admixture of a dense proliferation of small round cells resembling a primitive neuroectodermal tumor (PNET) and a pleomorphic spindle cell sarcomatous area. Abortive rosettes, primitive neural tube-like structures, and a few glandular structures were found in the small round cell area. Small round cells were immunoreactive for neural cell adhesion molecule and synaptophysin, but were not immunoreactive for MIC2 and neuron-specific enolase. Pleomorphic spindle cells were occasionally arranged in a storiform pattern and were diffusely immunoreactive for S-100 protein. The MPNST of small round cell type is distinguishable from PNET by its negative immunoreactivity for MIC2, and the present tumor is assumed to be derived from primitive neuroectodermal cells in the peripheral nerve capable of bidirectional (neuron and Schwann cell) differentiation.

The potential role of flow cytometry in the diagnosis of small cell carcinoma

CONTEXT

Virtually no information exists in the medical literature on the immunophenotyping of small cell carcinoma by flow cytometry. CD56, or neural cell adhesion molecule, is widely expressed by small cell carcinoma and easily measured by flow cytometry.

OBJECTIVE

To determine the potential usefulness of flow cytometry in the diagnosis of small cell carcinoma.

DESIGN AND SETTING

Retrospective data and archival material on 27 patients were obtained from community hospitals. Specimens (needle aspirations and tissue biopsies) from all patients demonstrated cytomorphologic and flow cytometric features consistent with small cell carcinoma. All measurements were performed at a large reference laboratory. Routine 3- and 4-color flow cytometry using a lymphoma antibody panel, including anti-CD56, was performed. Anti-cytokeratin antibody was also used in the last 12 cases. Immunohistochemical staining with a panel of conventional markers for neuroendocrine neoplasms was performed on available tissue for purposes of confirmation of small cell carcinoma.

PATIENTS

Twenty-seven patients whose tissue specimens showed a clearly defined population of CD45-CD56+ cells by flow cytometry and cytomorphologic features consistent with small cell carcinoma.

INTERVENTIONS

Needle aspiration (n = 3) and tissue biopsy (n = 24) from a variety of sites.

RESULTS

CD56 positivity by flow cytometry was 100 to 1000 times that of the matched isotype control in 25 cases and 10 to 100 times that of the control in 2 cases. Cytokeratin positivity by flow cytometry was found in 12 of 12 cases. Immunohistochemical staining showed positivity for at least 1 cytokeratin and 1 or more neuroendocrine markers in 26 of 27 cases and confirmed the diagnosis of small cell carcinoma.

CONCLUSIONS

Routine flow cytometry can identify a neuroendocrine phenotype that shows a strong correlation with confirmatory immunohistochemical markers in cases exhibiting cytomorphologic features of small cell carcinoma. Flow cytometry appears to complement and may possibly be a satisfactory alternative to immunohistochemical staining when small cell carcinoma is suspected.

Mediastinal rhabdomyoma: a case report and review of the literature

An incidental anterior-superior mediastinal rhabdomyoma is reported in a 68-year-old man who died of hypovolemic shock as a result of massive blood loss due to transection of aorta after being hit by a moving motor vehicle. This is the third reported case of mediastinal rhabdomyoma in the literature. The immunohistochemical evidence of expression of muscle-specific markers supports the rhabdomyomatous nature of this neoplasm, and electron microscopic demonstration of haphazardly arranged myofilaments with prominent Z bands, "jack-straws" in the mitochondria, and the absence of desmosomes is supportive of extracardiac origin of this rhabdomyoma. The possible histogenesis of extracardiac adult rhabdomyoma (EAR) in the anterior-superior mediastinum from the thymic myoid cells is also discussed.

Fine-needle aspiration biopsy of nonteratomatous germ cell tumors of the mediastinum

We assessed the usefulness of fine-needle aspiration biopsy (FNAB) in the diagnosis of mediastinal germ cell tumors (GCTs). In the archives of 3 pathology departments, we found records of 7 patients with mediastinal GCTs who underwent mediastinal FNAB as part of the diagnostic workup. The FNAB smears, results of the immunocytochemical analysis, the corresponding histologic findings, and the clinical charts were reviewed. All patients were men (age range, 24-44 years; mean, 32 years). One patient had a history of testicular mixed GCT 10 years earlier. The 6 primary mediastinal GCTs consisted of 3 seminomas and 3 yolk sac tumors. Based on the cytologic features and immunocytochemicalfindings, a cytologic diagnosis of GCT was made in 5 cases, including the case of metastatic GCT In 2 cases, the differential diagnosis was between poorly differentiated carcinoma and GCT Results of ancillary studies were noncontributory in 1 case, and the aspirate of the second case demonstrated extensive necrosis. Our findings demonstrate that a diagnosis of mediastinal GCT, primary or secondary, can be established with a high degree of accuracy on the basis of FNAB. Immunocytochemical analysis helps confirm the diagnosis.

Primary mediastinal giant cell tumors: a clinicopathologic and immunohistochemical study of two cases

Two cases of posterior mediastinal giant cell tumors are presented. The patients are a woman and a man, 31 and 18 years old, respectively. One of the patients had symptoms of paresthesias while the other was completely asymptomatic. Complete physical examination did not disclose evidence of tumor elsewhere. Neither patient had a previous history of malignancy. Surgical resection was performed. Histologically, both tumors were composed of a proliferation of osteoclast-like giant cells associated with a mononuclear cell population composed of oval and spindle cells. Mitotic activity and mild cellular atypia were present in the mononuclear cell component. No evidence of necrosis or hemorrhage could be demonstrated in either case. Immunohistochemically, both tumors showed strong positive reaction in the mononuclear component for antibodies against vimentin and CD68, while keratin, epithelial membrane antigen, CD45, S-100 protein, and desmin were negative. On clinical follow-up, both patients are alive and well without evidence of recurrence or metastasis 6 and 108 months after surgery. The present cases highlight the ubiquitous distribution of soft tissue giant cell tumors and the importance of considering these tumors in the differential diagnosis of posterior mediastinal neoplasms.

TIA-1+ cytotoxic large T-cell lymphoma of the mediastinum: case report

A 52-year-old previously healthy Caucasian woman presented with superior vena cava syndrome, secondary to compression of a bulky anterior mediastinal mass involving the right lung. Fine-needle aspiration biopsy of the mediastinum yielded large epithelioid cells intermingled with small mature lymphocytes. The epithelioid cells are LCA positive, expressing cytoplasmic CD3 diffusely and TIA-1 focally, but negative for EMA, CD4, CD8, CD15, CD20, CD30, and CD56. The TIA-1+ cytoplasmic granules correlated to the azurophilic granules in Diff-Quik-stained cells, pink granules in Ultrafast Papanicolaou-stained cells, and dense core granules in electron microscopy. In situ hybridization for Epstein-Barr viral RNA was negative. The background small lymphocytes were composed of a majority of CD4+ T-lymphocytes and minority of CD8+ T-lymphocytes. The patient responded well to six cycles of CHOP chemotherapy, followed by radiation with a total dose of 4140 cGy delivered to the mediastinum in 23 fractions. On the chest X-ray taken 6 mo later, there was minimal apical fibrosis with no evidence of an acute intrathoracic pathology. To the best of our knowledge, this case may be the first report of cytotoxic large T-cell lymphoma of the mediastinum.

Follicular dendritic cell tumor of the mediastinum

Follicular dendritic cell tumor (FDT) is a rare neoplasm usually occurring in the laterocervical lymph nodes, but presentations elsewhere are also well documented. We report a case of FDT in a 48-year-old man with myasthenia gravis, in whom a slow-growing mediastinal mass that had been surgically excised manifested after 3 years with a local recurrence in the same site. The lesion was aspirated and cytology showed a tumor composed of groups of oval or elongated cells intermingled with several mature small lymphocytes. On histology, the tumor was highly cellular with abundant perivascular lymphocytic infiltration; large cells with pale, eosinophilic cytoplasm and round nuclei, arranged in fascicles often showed a storiform pattern. Occasional binucleated cells were also present. A panel of antibodies showed positivity only for CD21 and CD35, and a weak response to S-100. Electron microscopy showed that the layer cells had convoluted nuclei and elongated interdigitating processes with desmosome-like junctions. The definitive diagnosis of FDT can be concluded only with positive immunostaining for CD21 and CD35. However, in the presence of a mixed population of lymphocytes and larger eosinophilic cells the hypothesis of FDT should always be considered.

Primary intrathoracic meningioma: histopathological, immunohistochemical and ultrastructural study of two cases

Meningiomas are common, usually benign slow-growing neoplasms of the central nervous system thought to arise from meningocytes capping arachnoid villi. Primary ectopic meningiomas are exceedingly rare extracranial and extraspinal tumors of controversial origin; they are usually limited to the head and neck region or to the paravertebral soft tissues. Only one mediastinal ectopic meningioma and few pulmonary ectopic meningiomas have been described in the literature until now. Because of their rarity and their intriguing pathogenesis, we report here a second case of primary mediastinal meningioma and an additional case of primary pulmonary meningioma. Their possible origin and differential diagnosis are discussed.

Benign glomus tumor of the superior posterior mediastinum

An unusual location of a benign glomus tumour, outside of the constantly located regions, e.g. in the subungual location or deeply sited in extremities, was diagnosed in a 56-year-old white female in her posterior upper mediastinum. The single similar case report was published before the era of electron microscopy and immunohistochemistry and single cases of atypical and malignant forms in this unusual location were published only recently. The tumour measuring 5 x 4 x 2 centimeters has caused cough and was associated with occasional righ-sided chest pain. Its rich vascular supply has caused intensive intraoperative bleeding. The postoperative course was uneventful and the patient is free of neoplastic disease or symptoms six years after surgery. Numerous mast cells present within the tumour's interstices must be considered in relation to the possible pathogenesis of the up to now unexplained pain in glomus tumours.

Small-cell variant of synovial sarcoma: fine-needle aspiration with ancillary features and potential diagnostic pitfalls

We report a small-cell variant of synovial sarcoma examined by fine-needle aspiration (FNA) biopsy. The patient is a 23-yr-old female who had a synovial sarcoma involving the left infratemporal region, diagnosed at 7 yr of age, followed by a metastatic lesion involving the lung and chest wall 16 yr later. The chest wall metastases was sampled by FNA biopsy. The aspirate consisted of numerous, small, round cells with very high nuclear-to-cytoplasmic ratios. The cytomorphologic features could potentially be confused with other pediatric small round cell tumors. Ancillary studies demonstrated positive staining of the neoplastic cells for cytokeratin, epithelial membrane antigen (EMA), and CD99. The differential diagnosis of other small round cell tumors that may be mistaken for the small-cell variant of synovial sarcoma are presented. We believe that this is the first FNA report detailing the cytologic and ancillary features of the small-cell variant of synovial sarcoma.

Thymic neuroendocrine carcinomas with combined features ranging from well-differentiated (carcinoid) to small cell carcinoma. A clinicopathologic and immunohistochemical study of 11 cases

We reviewed 11 cases of primary thymic neuroendocrine carcinomas with combined features ranging from well-differentiated to poorly differentiated neuroendocrine carcinoma. For 3 asymptomatic patients, tumors were discovered during routine examination. Presentation in the other patients was as follows: Cushing syndrome, 2 patients; chest pain, 3 patients; superior vena cava syndrome, 1 patient; and hypercalcemia and hypophosphatemia, 1 patient. No clinical data were available for the 11th patient. All tumors were located in the anterior mediastinum and treated by surgical excision. The lesions were large and well-circumscribed with areas of hemorrhage and necrosis. They were characterized by areas showing a proliferation of monotonous, round tumor cells adopting a prominent organoid pattern admixed with areas showing sheets of atypical cells with hyperchromatic nuclei, frequent mitoses, and extensive areas of hemorrhage and necrosis. Immunohistochemical studies performed in 6 cases showed strong CAM 5.2 low-molecular-weight cytokeratin positivity in all cases, chromogranin and synaptophysin positivity in 4, Leu-7 in 3, and focal positivity for p53 in 2. Follow-up information for 9 cases showed that all patients died of their tumors between 1 and 4 years after diagnosis. The present cases highlight the heterogeneity of neuroendocrine neoplasms and reinforce the notion that these tumors form part of a continuous spectrum of differentiation.

Disseminated metastasis of neuroblastomatous component in immature mediastinal teratoma: a case report

A 17-year-old man with high levels of serum AFP and hCG was diagnosed as having primary mediastinal GCT. Cisplatin-based chemotherapy decreased the biomarkers, but the mass showed further growth. Pathological examination of the resected mass revealed a mixture of immature and mature teratomas. Six months after the surgery, the patient died of a dissemination of neuroblastomatous cells, which were similar to those in the immature neural component of the primary tumor. A disseminated metastasis of neuroblastoma in immature mediastinal teratoma is a rare complication. Serum NSE can be a useful marker in detecting the metastasis.

Neuroendocrine carcinoma of the posterior mediastinum: a possible primary lesion

A paravertebral mass was noted in the posterior mediastinum in a 47-year-old man. Microscopically, the tumor showed solid and trabecular patterns and consisted of poorly differentiated atypical cells that often formed Flexner-Wintersteiner rosettelike glands. Immunohistochemically, the tumor cells expressed both epithelial and neuroendocrine markers, including cytokeratin (AE1/3), carcinoembryonic antigen, epithelial membrane antigen, neuron-specific enolase, chromogranin A, and synaptophysin, but were negative for CD99 (MIC2). Ultrastructurally, numerous desmosomes and neurosecretory granules were identified in the tumor cells. The present lesion was a primary neuroendocrine carcinoma of the posterior mediastinum-an unusual site for such a lesion.

CD30 expression is common in mediastinal large B-cell lymphoma

Large B-cell lymphoma manifesting in the mediastinum shows distinctive clinical and immunophenotypic features and is recognized as a unique type of large B-cell lymphoma in the Revised European-American Lymphoma classification. Fifty-one cases of primary mediastinal large B-cell lymphoma were retrieved from the immunodiagnosis laboratory database files and were stained with anti-CD30 (Ber-H2). Of the 51 cases, 35 (69%) stained for CD30. This staining ranged from strong membrane staining of all or almost all of the neoplastic cells to positivity of rare individual cells. Eleven cases (22%) were negative; 4 (8%) were equivocal. Only 1 case was uninterpretable owing to B-5 fixation and lack of a positive internal control. Thus, the majority of mediastinal large B-cell lymphomas express the Hodgkin marker CD30. This finding may result in misdiagnosis of large cell lymphoma as Hodgkin disease.

An autopsy case of a malignant pericardial mesothelioma in a Japanese young man

An autopsy case of a malignant pericardial mesothelioma in a 27-year-old man with no history of exposure to asbestos is reported. He was admitted for heart failure due to pericardial effusion of unknown origin and surgically drained, but later died. The diagnosis of a malignant pericardial mesothelioma was made on the basis of histologic, immunohistochemical and ultrastructural findings. The tumor was located on the pericardium, but autopsy revealed that it had spread extensively in the mediastinum and the lungs. Microscopically, the tumor cells were epithelial like and contained histochemically demonstrable glycogen and hyaluronic acid. Immunohistochemical studies of the tumor demonstrated positive immunoreactivity for cytokeratin 19, muscle actin HHF35, epithelial membrane antigen, CA125, p53 and p21WAF1/CIP1 whereas the tumor was negative for cytokeratins 10 and 17, carcinoembryonic antigen, vimentin, epithelial antigen BerEP4, S-100, c-erbB2 and bcl-2. A high MIB-1 labeling index was noted. Under the electron microscope the tumor cells exhibited long, thin villi. The operation and autopsy findings thus revealed this to be a very rare case of malignant pericardial mesothelioma in a young man.

Malignant melanoma presenting as a mediastinal mass

A case of malignant melanoma presenting as a mediastinal mass without an extrathoracic primary is reported. Microscopically the tumor appeared consistent with malignant melanoma, with the presence of focal melanin pigment in large epithelioid cells. Fontana stain confirmed the presence of melanin pigment. Immunohistochemical staining further suggested melanoma, with the tumor cells expressing a HMB45+, S100+ and cytokeratin-phenotype. Electron microscopy showed an abundance of melanosomes confirming the diagnosis of malignant melanoma.

Metastatic carcinoma of the prostate mimicking primary carcinoid tumor of the lung and mediastinum

Although prostatic carcinomas rarely present as intrathoracic metastases, they may occasionally exhibit clinical and radiographic findings suggestive of a primary pulmonary carcinoid, particularly when they have a cribriform pattern. This report describes three patients who presented with lung and mediastinal neoplasms initially diagnosed as primary carcinoid tumors. These tumors were later proven to be metastatic prostate carcinoma by the use of immunohistochemical studies, including stains for chromogranin, carcinoembryogenic antigen and prostate specific antigen. These findings emphasize the importance of considering metastatic prostate adenocarcinoma in the differential diagnosis of carcinoid or neuroendocrine carcinoma with a cribriform pattern.

Ossifying fibromyxoid tumour of soft parts: report of four cases including one mediastinal and one infantile

Four cases of ossifying fibromyxoid tumour of soft parts are described. One of them was in the mediastinum, a hitherto unreported location of this rare neoplasm. Another was removed from the subcutaneous tissue of the head of a two-year-old girl, the youngest patient so far described. A peculiar feature of this tumour was haphazard spindle cell groups showing smooth muscle differentiation. One tumour was remarkably proliferative with 20 mitotic figures per 10 high power fields and 50% of cells positive for Ki-67 antigen. Immunohistochemical analysis revealed that all the tumours were diffusely positive for vimentin, and focally for S-100-protein. In addition to this the infantile tumour expressed focal alpha-smooth muscle actin, desmin and glial fibrillary acidic protein, while the mediastinal tumour expressed only alpha-smooth muscle actin and the highly proliferative one expressed none of these antigens. Background cells, including histiocytes, lymphocytes and mast cells were numerous. DNA cytometry analysis using both static and flow methods showed that the mediastinal tumour contained two cell clones, while the others were diploid. The proliferative fraction of cells (S plus G2 phases) was prominent in the proliferative and infantile tumours.

Fine-needle aspiration biopsy of metastatic Ewing's sarcoma with MIC2 (CD99) immunocytochemistry

The use of fine-needle aspiration biopsy (FNAB) has been infrequently described as a diagnostic modality for Ewing's sarcoma (ES) patient follow-up and management. The purpose of this study is to examine the use and accuracy of FNAB combined with MIC2 immunocytochemistry for evaluating metastases in patients with ES. Records from Saint Louis University Health Sciences Center and Indiana University Medical Centers identified patients with known ES who had undergone FNAB for evaluation of potential metastases. Immunocytochemical analysis for MIC2 (CD99) was performed retrospectively on cell blocks and direct aspirate smears. FNABs from nine patients were procured either percutaneously or under radiologic guidance and in all cases a definitive cytologic diagnosis of metastatic ES was rendered. Aspirates were cellular with many single discohesive small round cells and occasional loosely cohesive clusters. The nuclei were round with a fine chromatin pattern and small nucleoli. The cytoplasm was scanty and the nuclear-cytoplasmic ratio was high. Six of six cases showed strongly positive immunocytochemical labeling for MIC2. Immunocytochemistry with MIC2 in FNAB aspirate smears can provide supportive evidence of ES in patients with known disease.

Mediastinal granulocytic sarcoma: a report of two cases

We describe the cases of two patients who presented with granulocytic sarcoma with mediastinal involvement 15 and 21 months before development of acute myeloid leukemia. In both cases several bone marrow aspirates and trephine biopsy specimens, obtained at presentation and subsequently, revealed no evidence of leukemic infiltration. One case was originally misdiagnosed as large-cell non-Hodgkin's lymphoma, which resulted in inappropriate therapy. In both cases immunohistochemical staining revealed that tumor cells were positive for leucocyte common antigen but not for conventional B- or T-lymphoid-cell markers. Retrospective analysis revealed that tumor cells in both cases were positive for myeloid markers. Histopathologists should be aware that granulocytic sarcoma may occur in unusual extramedullary sites without evidence of bone marrow involvement. If inappropriate treatment is to be avoided, a diagnosis of granulocytic sarcoma should be considered when hemopoietic tumor cells do not stain with conventional antibodies against B- and T-lymphoid cells. Both histochemical and immunohistochemical staining should be performed in such cases to determine whether the cells are of myeloid lineage. A diagnosis of granulocytic sarcoma is not ruled out when bone marrow biopsy specimens show no evidence of leukemic infiltration.

Lipoleiomyosarcoma of the mediastinum

A case is described of a mediastinal soft tissue sarcoma, in a 76-year-old man, characterized microscopically by the intimate combined features of liposarcoma and leiomyosarcoma. The lipomatous component consisted of well differentiated liposarcoma with myxoid areas. The smooth muscle component was characterized by fascicles of spindle cells showing nuclear atypia and scattered mitoses. The spindle cells displayed intense reactivity for alpha smooth muscle actin (ASMA), desmin and vimentin. Differential diagnoses included dedifferentiated liposarcoma, spindle cell liposarcoma, angiomyolipoma and myolipoma. To the best of our knowledge no case of sarcoma in the mediastinum with combined features of liposarcoma and leiomyosarcoma has been reported. The dual lineage differentiation of the lipoleiomyosarcoma may be difficult to identify in small biopsy samples which may not represent the tumor as a whole. Lipoleiomyosarcoma should be included in the differential diagnosis of soft tissue tumors arising in the mediastinum.

Hepatoid yolk sac tumors of the mediastinum: a clinicopathologic and immunohistochemical study of four cases

Four cases of primary hepatoid yolk sac tumors of the anterior mediastinum are described. The patients were all men between the ages of 26 and 40 years (median 33). Clinically, they all presented with a history of shortness of breath and chest pain of several weeks' duration. None of the patients had a history of germ cell tumor elsewhere or evidence of any hepatic abnormality. Grossly, all the tumors were described as large mediastinal masses that impinged on adjacent structures. Histologically, they were characterized by sheets of medium-sized, round to polygonal neoplastic cells with moderate amounts of eosinophilic cytoplasm and round to oval nuclei with prominent nucleoli. The cellular proliferation was homogeneous and displayed moderate cellular atypia and scattered mitotic activity. All the tumors showed focally the presence of more conventional areas of yolk sac tumor, with islands of tumor cells showing a reticular pattern of growth admixed with scattered intra- and extracellular hyaline globules and occasional Schiller-Duval bodies. Immunohistochemical studies showed strong positivity of the tumor cells for alpha-fetoprotein in both components of the lesions. Follow-up information was available in three patients, all of whom developed lung metastases within a year after initial diagnosis. Two of these patients died of tumor within the same period, whereas a third patient has been lost to follow-up. The present cases illustrate an unusual histologic pattern of yolk sac tumor in the mediastinum and highlight the importance of considering this tumor in the differential diagnosis of lesions showing a hepatoid pattern of growth in the mediastinal area.