Paratesticular mesothelial proliferations

Benign Mesothelial Proliferations of the Tunica Vaginalis Testis

The correct diagnosis of mesothelial proliferations is a classic problem for pathologists, and one which has important clinical implications. A significant number of such cases appear associated with recurrent hydrocele, as an irritative/reactive response to this condition. The morphological spectrum of mesothelial lesions in this topography is broad, and a set of benign conditions may appear, sometimes with florid gross features and cytologic pseudo-atypia. Here, we present two different examples in which malignancy was initially considered in the differential diagnosis.

Lymphatic Endothelial Cell in Endemic Bancroftian Filariasis: A Focus on the Lymphatics of the Tunica Vaginalis Testis

Background

In endemic areas, lymphangiectasia is the fundamental alteration to live Wuchereria bancrofti adult worms which, in adult males, are usually found in the lymphatic vessels of the spermatic cord; accordingly, hydrocele/filaricele is the most common clinical manifestation of bancroftian filariasis. The pathogenic role of the lymphatic endothelial cells (LECs) and the status of mesothelial cells (MCs) samples of the parietal layer (PL) of the tunica vaginalis testis were examined.

Methods

The PL of thirty-two patients, excised for different reasons, was examined by histology and immunohistochemistry using the D2-40 monoclonal antibody for identification of LECs and CK-7 antibody for recognition of mesothelial cells (MCs).

Results

The most important findings were (a) marked lymphangiectasia, especially in hydroceles with minor evolution time; (b) the first report of lymphatic stomata and submesothelial lacunae in filarial acute hydrocele; (c) the likely participation of LECs in filarial granuloma; (d) the potential phenotypic transition of LECs into myofibroblasts in severe chylocele; and (e) mesothelial reactive hyperplasia, a hallmark of filaricele, varying in intensity from mild to severe, sometimes mimicking a mesothelial neoplasia.

Conclusion

The data suggest that LECs have an active role in the pathogenesis of bancroftian hydrocele and, possibly, in other clinical forms of lymphatic filariasis.

The legacy of the F344 rat as a cancer bioassay model (a retrospective summary of three common F344 rat neoplasms)

The Fischer 344 (F344) rat was used by the National Toxicology Program (NTP) for over 5 decades for toxicity and carcinogenicity studies. However, in 2006, the NTP decided to switch to a different rat stock due largely to high background control incidences of Leydig cell tumors (LCTs) and mononuclear cell leukemia (MNCL), also known as large granular lymphocytic (LGL) leukemia. In the current review, we aim (1) to provide a summary of NTP bioassays with treatment-associated effects involving MNCL and LCTs in addition to male F344-specific tunica vaginalis mesothelioma (TVM); (2) to describe important pathobiological differences between these F344 rat tumor responses and similar target tissue-tumor response in humans; and (3) to present the NTP reasons for switching away from the F344 rat. We show that due to the highly variable background incidence of F344 MNCL, more reliance on historical control data than is usual for most tumor responses is warranted to evaluate potential effect of any chemical treatment in this rat strain. The high spontaneous incidence of LCTs in the testes of male F344 rats has made this tumor endpoint of little practical use in identifying potential testicular carcinogenic responses. TVM responses in F344 rats have a biological plausible relationship to LCTs unlike TVM in humans. Given their high spontaneous background incidence and species-specific biology, we contend that MNCL and LCT, along with TVM responses, in F344 rat carcinogenicity studies are inappropriate tumor types for human health risk assessment and lack relevance in predicting human carcinogenicity.

Well-differentiated papillary mesothelioma of the tunica vaginalis: a case study and review of the literature

Well-differentiated papillary mesothelioma is an uncommon tumor of the testes that usually presents as a hydrocele. Here, we present the case of one patient who did not have a history of asbestos exposure. The tumor was localized in the tunica vaginalis and was composed of three pedunculated masses macroscopically. Microscopically, branching papillary structures with focal coagulative necrosis were present. In addition to immunohistochemistry, simian virus 40 DNA was also tested by polymerase chain reaction. This report presents one case of this rare entity, its clinical and macroscopic features, and follow-up results.

Malignant paratesticular mesothelioma

Mesothelioma of the tunica vaginalis testis (MTVT) is a rare tumor that usually affects patients after the sixth decade of life. Exposure to asbestos is a known risk factor. Enlargement of the scrotal volume is the most common initial clinical manifestation, and about 15% of cases present metastasis at diagnosis. The treatment relies on surgical resection while the role of adjuvant chemotherapy and radiotherapy remains unclear. The prognosis for patients is generally poor, with a lethal outcome in 30% over a 24-month period. The authors report a case of a 62-year-old patient with the diagnosis of MTVT without a history of asbestos exposure. After surgical treatment, metastatic disease ensued. Chemotherapy was initiated, but could not be continued due to marked and fast clinical deterioration. The authors call attention to the difficulty of early diagnosis of MTVT due to a nonspecific clinical picture, the lack of action by the patient when the scrotal enlargement was first noticed, and the lack of tumor markers. Delayed diagnosis is definitely related to unfavorable prognosis.

Malignant paratesticular mesothelioma

Mesothelioma of the tunica vaginalis testis (MTVT) is a rare tumor that usually affects patients after the sixth decade of life. Exposure to asbestos is a known risk factor. Enlargement of the scrotal volume is the most common initial clinical manifestation, and about 15% of cases present metastasis at diagnosis. The treatment relies on surgical resection while the role of adjuvant chemotherapy and radiotherapy remains unclear. The prognosis for patients is generally poor, with a lethal outcome in 30% over a 24-month period. The authors report a case of a 62-year-old patient with the diagnosis of MTVT without a history of asbestos exposure. After surgical treatment, metastatic disease ensued. Chemotherapy was initiated, but could not be continued due to marked and fast clinical deterioration. The authors call attention to the difficulty of early diagnosis of MTVT due to a nonspecific clinical picture, the lack of action by the patient when the scrotal enlargement was first noticed, and the lack of tumor markers. Delayed diagnosis is definitely related to unfavorable prognosis.

Epithelioid Lesions of the Serosa

Context.—Diagnosing epithelioid serosal lesions remains a challenge because numerous different processes—primary or secondary, benign or malignant—occur in body cavities, some of which are very rare.

Objectives.—To review the newest literature and to describe the morphologic criteria and immunohistochemical markers that are useful for distinguishing epithelioid serosal lesions.

Data Sources.—Previously published literature concentrating on the newest research findings. Earlier reviews are principally referred to for established diagnostic criteria.

Conclusions.—Immunohistochemistry with a panel of antibodies has made the diagnosis of epithelioid serosal lesions very reliable. When deciding on antibodies used in differential diagnosis, it is important to consider tumor location, clinical and radiologic information, and morphologic features. Immunohistochemistry is less useful in the differential diagnosis of benign versus malignant mesothelial lesions. The diagnosis of benign versus malignant mesothelial proliferations still relies on the histologic criteria of invasion.

Mesothelioma of tunica vaginalis of "uncertain malignant potential" - an evolving concept: case report and review of the literature

Mesothelioma of tunica vaginalis is a rare neoplasm, typically demonstrating frankly malignant morphology and aggressive behavior. Rare cases of well-differentiated papillary mesotheliomas have also been reported, which, in contrast, demonstrate indolent behavior. There are, however, cases which do not fit into the well-differentiated or diffuse malignant mesothelioma categories and can be considered mesothelioma of tunica vaginalis of "uncertain malignant potential", which is an emerging diagnostic category. A 57-year-old man presented with a neoplasm in a hydrocele sac. The neoplasm was non-invasive, but showed focal complex and solid growth and it was difficult to categorize either as well-differentiated papillary mesotheliomas or malignant mesothelioma. After the initial limited resection, the patient underwent radical orchiectomy with hemiscrotectomy and is alive and without disease progression after 6 years. Documentation of these rare tumors will allow their distinction from true malignant mesotheliomas and will facilitate the development of specific treatment recommendations.

Mesothelioma of tunica vaginalis of "uncertain malignant potential" - an evolving concept: case report and review of the literature

Mesothelioma of tunica vaginalis is a rare neoplasm, typically demonstrating frankly malignant morphology and aggressive behavior. Rare cases of well-differentiated papillary mesotheliomas have also been reported, which, in contrast, demonstrate indolent behavior. There are, however, cases which do not fit into the well-differentiated or diffuse malignant mesothelioma categories and can be considered mesothelioma of tunica vaginalis of "uncertain malignant potential", which is an emerging diagnostic category. A 57-year-old man presented with a neoplasm in a hydrocele sac. The neoplasm was non-invasive, but showed focal complex and solid growth and it was difficult to categorize either as well-differentiated papillary mesotheliomas or malignant mesothelioma. After the initial limited resection, the patient underwent radical orchiectomy with hemiscrotectomy and is alive and without disease progression after 6 years. Documentation of these rare tumors will allow their distinction from true malignant mesotheliomas and will facilitate the development of specific treatment recommendations.

Paratesticular mesothelioma. Report of a case with comprehensive review of literature

Paratesticular mesotheliomas are rare tumors with 223 cases described so far. The sole plausible causative factor so far ascertained in the pathogenesis of these tumors is asbestos, which however is found in only around 30% to 40% of such cases. The age range of affected individuals is wide, mostly adults and the elderly, but also includes young people and children. The most common presenting symptom is either hydrocele of unknown origin or intrascrotal mass. When hydrocele is the presenting symptom, these tumors are often clinically overlooked and the diagnosis is delayed. Most paratesticular mesotheliomas arise in the tunica vaginalis, but primary tumors of the spermatic cord and epididymis are also on record. Tumors arising from the peritoneal mesothelium of a hernia sac are excluded from this group. The correct diagnosis is almost always made after histologic examination of the operative specimen. Immunohistochemistry and electron microscopy are always helpful and sometimes necessary tools for diagnosis. So far very few cases have been identified or suspected preoperatively on cytologic examination. Three clinicopathologic types of malignant mesotheliomas of the male genital tract are recognized: diffuse tubulo-papillary mesothelioma, well-differentiated papillary mesothelioma, and multicystic mesothelioma. The histologic subtypes are almost always pure epithelial or biphasic. The differential diagnosis is mainly with serous papillary tumors arising from Mullerian vestiges, but several diverse primary or secondary tumors also need to be considered. A clinicopathologic evaluation of a case of tunical diffuse mesothelioma in a 74-year-old male from the AMR Series is the starting point for this general review.

Benign and Malignant Neoplasms of the Testis and Paratesticular Tissue

Benign and malignant tumors of the testes and paratesticular tissues present an interesting spectrum of diagnostic entities often encountered in routine surgical pathology practice. Germ cell tumors are the most common tumors of the testes and, despite a rising incidence, have excellent prognosis because of their radiosensitivity and/or effective chemotherapeutic agents. The proper classification of these tumors aids in the choice of appropriate treatment options. This article reviews benign and malignant neoplastic entities of the testes and paratesticular tissues and illustrates the classic pathologic characteristics. The differential diagnosis, along with ancillary studies, clinical significance, and presentation are discussed also.

Mesothelial Glandular Structures Within Pseudosarcomatous Proliferative Funiculitis—A Diagnostic Pitfall: Report of 17 Cases

We describe 17 cases of distinct benign pseudomalignant mesothelial proliferations, involving the spermatic cord. All cases revealed necrosis. The areas adjacent to the necrotic tissue comprised a cellular spindle cell proliferation with a haphazard arrangement of the myofibroblasts that in many areas revealed transitions into plump oval epithelioid cells and into cells with genuine epithelial appearances arranged in linear cords and often luminized into small microcysts. These epithelial cells formed isolated groups with glandular structures arising on the myofibroblastic background. Glandular structures were often situated deeply in the stroma of the spermatic cords. All cellular elements were strongly positive with AE1/AE3 antibody. All myofibroblasts stained with SM-actin antibody. Ultrastructurally, the spindle cells displayed features of myofibroblasts including actin microfilaments, as did the plump epithelioid cells that, additionally, had desmosomes, and the cords of the epithelial cells including those forming glandular structures had characteristics of mesothelias including the characteristic microvilli.

Mesothelioma of the tunica vaginalis testis: a rare malignancy mimicking more common inguino-scrotal masses

Malignant pleural mesotheliomas are rare malignancies associated with asbestos exposure and these tumors are infamous for their poor prognosis. Mesotheliomas in other body areas are much rarer. They may occur in the abdominal cavity and also in the inguinal region. In the latter area they are commonly confused with much commoner benign conditions. We present three cases of mesotheliomas in the tunica vaginalis testis.

The immunohistochemical profile of malignant mesotheliomas of the tunica vaginalis: a study of 20 cases

Malignant mesotheliomas of the testis arise from the tunica vaginalis, formed from the evagination of the abdominal peritoneum into the scrotum. The immunohistochemical profile of the tunica vaginalis and associated neoplasms is often extrapolated from thoracic studies. Testicular series are uncommon, usually derived from previous case studies and literature reviews. The immunohistochemical findings in 20 cases originally diagnosed as malignant mesotheliomas are presented. Archival testicular malignant mesothelioma specimens from 1959 to 2004 were collected from hospitals throughout the United Kingdom and from the authors' own archives. Hematoxylin and eosin-stained sections were reviewed, and selected sections from each case were then examined using an immunohistochemical panel of eight antibodies: calretinin (Zymed, 1:200), epithelial membrane antigen (EMA) (DAKO, 1:50), thrombomodulin (DAKO 1:5), CK7 (DAKO, 1:100), CK5-CK6 (DAKO, 1:10), BerEp4 (DAKO, 1:25), carcinoembryonic antigen (CEA) (DAKO, 1:10), and CK20 (DAKO, 1:100). The EnVision technique was used for all antibodies. Sections were reviewed independently by three pathologists. Electron microscopy was performed on selected cases. In all cases, the morphologic light microscopy criteria for a diagnosis of malignant mesothelioma were present. However, two tumors were later excluded from the study because of diffuse strong positive immunostaining with CK20 and BerEp4 and an ultrastructural appearance of adenocarcinoma. Of the remaining cases, 15 of 18 (83%) were purely epithelioid in type, showing a mixture of papillary, tubular, and solid patterns, and 3 of 18 (17%) showed a mixed sarcomatoid/epithelioid pattern. All cases were positive for calretinin and EMA (100%), 16 of 18 (89%) were positive for thrombomodulin, and 15 of 18 (83%) were positive for CK7. CK5-CK6 positivity was present in 13 of 18 (72%) but varied in strength and distribution; 2 of 18 (11%) were positive for BerEp4. All the cases were negative for CK20 and CEA. Four of the 18 cases were examined by electron microscopy, which revealed long thin microvilli supporting a diagnosis of malignant mesothelioma. This study has shown that the immunocytochemical profile of testicular malignant mesotheliomas is similar to those arising in the pleura, with diffuse positivity for calretinin, EMA, thrombomodulin, and CK7, and negative for CK20 and CEA. Focal weak positivity may be encountered with BerEp4. However, histopathologists should be aware of the variability in CK5-6 staining in testicular specimens when compared with pleural mesotheliomas.

Well-differentiated papillary mesothelioma occurring in the tunica vaginalis of the testis with contralateral atypical mesothelial hyperplasia

Well-differentiated papillary mesothelioma (WDPM) occurs rarely in the paratesticular region, with only a handful of published case reports. Often presenting with recurrent hydrocele, WDPM is a multifocal mesothelial proliferation with a predominantly indolent clinical course. Accordingly, pathologic distinction of this lesion from true malignant mesothelioma is crucial, although it may be difficult because of the variability of associated histologic features. In addition, rare cases of WDPM have progressed to malignant mesothelioma, leading to its classification as a tumor of low malignant potential. Here, we report a case of multifocal WDPM occurring in the tunica vaginalis and tunica albuginea, with contralateral atypical mesothelial hyperplasia, a potentially premalignant lesion.