WHO 2022 classification of penile and scrotal cancers: updates and evolution.

Squamous cell carcinoma (SCC) is the most common malignant tumour of the penis. The 2022 WHO classification reinforces the 2016 classification and subclassifies precursor lesions and tumours into human papillomavirus (HPV)-associated and HPV-independent types. HPV-associated penile intraepithelial neoplasia (PeIN) is a precursor lesion of invasive HPV- associated SCC, whereas differentiated PeIN is a precursor lesion of HPV-independent SCC. Block-type positivity of p16 immunohistochemistry is the most practical daily utilised method to separate HPVassociated from HPVindependent penile SCC. If this is not feasible, the term SCC, not otherwise specified (NOS) is appropriate. Certain histologies that were previously classified as "subtypes" are now grouped, and coalesced as "patterns", under the rubric of usual type SCC and verrucous carcinoma (e.g. usual-type SCC includes pseudohyperplastic and acantholytic/pseudoglandular carcinoma, and carcinoma cuniculatum is included as a pattern of verrucous carcinoma). If there is an additional component of the usual type of invasive SCC (formerly termed hybrid histology), the tumour would be a mixed carcinoma (e.g. carcinoma cuniculatum or verrucous carcinoma with usual invasive SCC); in such cases, reporting of the relative percentages in mixed tumours may be useful. The consistent use of uniform nomenclature and reporting of percentages will inform the refinement of future reporting classification schemes and guidelines/recommendations. The classification of scrotal tumours is provided for the first time in the fifth edition of the WHO Blue book, and it follows the schema of penile cancer classification for both precursor lesions and the common SCC of the scrotum. Basal cell carcinoma of the scrotum may have a variable clinical course and finds a separate mention.

Dataset for the reporting of carcinoma of the bladder-cystectomy, cystoprostatectomy and diverticulectomy specimens: recommendations from the International Collaboration on Cancer Reporting (ICCR).

The International Collaboration on Cancer Reporting (ICCR) is a not for profit organisation whose goal is to produce standardised internationally agreed and evidence-based datasets for pathology reporting. With input from pathologists worldwide, the datasets are intended to be uniform and structured. They include all items necessary for an objective and accurate pathology report which enables clinicians to apply the best treatment for the patient. This dataset has had input from a multidisciplinary ICCR expert panel. The rationale for some items being required and others recommended is explained, based on the latest literature. The dataset incorporates data from the World Health Organization (WHO) 2016, and also from the latest (8th edition) TNM staging system of the American Joint Committee on Cancer (AJCC). Fifteen required elements and eight recommended items are described. This dataset provides all the details for a precise and valuable pathology report required for patient management and prognostication. This dataset is intended for worldwide use, and should facilitate the collection of standardised comparable data on bladder carcinoma at an international level.

Dataset for the reporting of urinary tract carcinoma-biopsy and transurethral resection specimen: recommendations from the International Collaboration on Cancer Reporting (ICCR).

The International Collaboration on Cancer Reporting (ICCR) is an alliance of major pathology organisations in Australasia, Canada, Europe, United Kingdom, and United States of America that develops internationally standardised, evidence-based datasets for the pathology reporting of cancer specimens. This dataset was developed by a multidisciplinary panel of international experts based on previously published ICCR guidelines for the production of cancer datasets. It is composed of Required (core) and Recommended (noncore) elements identified on the basis of literature review and expert consensus. The document also includes an explanatory commentary explaining the rationale behind the categorization of individual data items and provides guidance on how these should be collected and reported. The dataset includes nine required and six recommended elements for the reporting of cancers of the urinary tract in biopsy and transurethral resection (TUR) specimens. The required elements include specimen site, operative procedure, histological tumor type, subtype/variant of urothelial carcinoma, tumor grade, extent of invasion, status of muscularis propria, noninvasive carcinoma, and lymphovascular invasion (LVI). The recommended elements include clinical information, block identification key, extent of T1 disease, associated epithelial lesions, coexistent pathology, and ancillary studies. The dataset provides a structured template for globally harmonized collection of pathology data required for management of patients diagnosed with cancer of the urinary tract in biopsy and TUR specimens. It is expected that this will facilitate international collaboration, reduce duplication of effort in updating current national/institutional datasets, and be particularly useful for countries that have not developed their own datasets.

[The 2014 consensus conference of the ISUP on Gleason grading of prostatic carcinoma]. / Konsenskonferenz 2014 der ISUP zur Gleason-Graduierung des Prostatakarzinoms.

In 2005 the International Society of Urological Pathology (ISUP) held a concensus conference on Gleason grading in order to bring this grading system up to the current state of contemporary practice; however, it became clear that further modifications on the grading of prostatic carcinoma were necessary. The International Society of Urological Pathology therefore held a further consensus conference in 2014 to clarify these points. This article presents the essential results of the Chicago grading meeting.

Validation of International Society of Urological Pathology (ISUP) grading for prostatic adenocarcinoma in thin core biopsies using TROG 03.04 'RADAR' trial clinical data.

In 2014 a consensus conference convened by the International Society of Urological Pathology (ISUP) adopted amendments to the criteria for Gleason grading and scoring (GS) for prostatic adenocarcinoma. The meeting defined a modified grading system based on 5 grading categories (grade 1, GS 3+3; grade 2, GS 3+4; grade 3, GS 4+3; grade 4, GS 8; grade 5, GS 9-10). In this study we have evaluated the prognostic significance of ISUP grading in 496 patients enrolled in the TROG 03.04 RADAR Trial. There were 19 grade 1, 118 grade 2, 193 grade 3, 88 grade 4 and 79 grade 5 tumours in the series, with follow-up for a minimum of 6.5 years. On follow-up 76 patients experienced distant progression of disease, 171 prostate specific antigen (PSA) progression and 39 prostate cancer deaths. In contrast to the 2005 modified Gleason system (MGS), the hazards of the distant and PSA progression endpoints, relative to grade 2, were significantly greater for grades 3, 4 and 5 of the 2014 ISUP grading scheme. Comparison of predictive ability utilising Harrell's concordance index, showed 2014 ISUP grading to significantly out-perform 2005 MGS grading for each of the three clinical endpoints.

[Vancouver classification of renal tumors: Recommendations of the 2012 consensus conference of the International Society of Urological Pathology (ISUP)]. / Vancouver-Klassifikation von Nierentumoren : Empfehlungen der Konsenskonferenz der Internationalen Gesellschaft für Uropathologie (ISUP) 2012.

The 2012 consensus conference of the International Society of Urological Pathology (ISUP) has formulated recommendations on classification, prognostic factors and staging as well as immunohistochemistry and molecular pathology of renal tumors. Agreement was reached on the recognition of five new tumor entities: tubulocystic renal cell carcinoma (RCC), acquired cystic kidney disease-associated RCC, clear cell (tubulo) papillary RCC, microphthalmia transcription factor family RCC, in particular t(6;11) RCC and hereditary leiomyomatosis-associated RCC. In addition three rare forms of carcinoma were considered as emerging or provisional entities: thyroid-like follicular RCC, succinate dehydrogenase B deficiency-associated RCC and anaplastic lymphoma kinase (ALK) translocation RCC. In the new ISUP Vancouver classification, modifications to the existing 2004 World Health Organization (WHO) specifications are also suggested. Tumor morphology, a differentiation between sarcomatoid and rhabdoid and tumor necrosis were emphasized as being significant prognostic parameters for RCC. The consensus ISUP grading system assigns clear cell and papillary RCCs to grades 1-3 due to nucleolar prominence and grade 4 is reserved for cases with extreme nuclear pleomorphism, sarcomatoid and/or rhabdoid differentiation. Furthermore, consensus guidelines were established for the preparation of samples. For example, agreement was also reached that renal sinus invasion is diagnosed when the tumor is in direct contact with the fatty tissue or loose connective tissue of the sinus (intrarenal peripelvic fat) or when endothelialized cavities within the renal sinus are invaded by the tumor, independent of the size. The importance of biomarkers for the diagnostics or prognosis of renal tumors was also emphasized and marker profiles were formulated for use in specific differential diagnostics.

[Diagnostics of radical prostatectomy specimens. Results of the 2009 consensus conference of the International Society of Urological Pathology]. / Diagnostik radikaler Prostatektomiepräparate. Ergebnisse der Konsensuskonferenz der Internationalen Gesellschaft für Urologische Pathologie 2009.

The 2009 consensus conference of the International Society of Urological Pathology (ISUP) made recommendations for standardization of handling and staging of radical prostatectomy specimens. The conference topics were preparation of specimens, the T2 subclassification, prostate cancer volume, extraprostatic tumor extent, lymphovascular invasion, seminal vesicle infiltration, lymph node metastases and surgical margins. This review article presents the essential results and recommendations of this conference.

Leiomyosarcoma of urinary bladder following cyclophosphamide therapy: report of two cases.

Leiomyosarcoma of urinary bladder is rare, although it is the most common mesenchymal tumor in adults. We report two cases of this tumor following cyclophosphamide therapy. The first case is from a 53-year-old man with Wegener's granulomatosis treated for 6 years with cyclophosphamide. He presented with painless hematuria, and the initial biopsy of the bladder tumor revealed a malignant spindle cell neoplasm. A final diagnosis of leiomyosarcoma was made on radical cystoprostatectomy. The second example is from a 21-year-old man who had received cyclophosphamide in early infancy for a bilateral retinoblastoma. He also presented with painless hematuria, and a bladder tumor was resected transurethrally and diagnosed as leiomyosarcoma. He underwent partial cystectomy two months later. Cyclophosphamide, when used for a neoplastic or non-neoplastic condition, is associated with an increased risk of developing bladder cancer. The distribution of histologic subtypes differs from that seen in spontaneous bladder tumors. A review of the literature shows an increased proportion of squamous cell carcinomas and sarcomas, especially leiomyosarcomas in cyclophosphamide exposed patients. Acrolein, a cytotoxic metabolite of cyclophosphamide excreted in urine, is regarded as the most likely causative agent.

Dermoid cyst of the testis: a study of five postpubertal cases, including a pilomatrixoma-like variant, with evidence supporting its separate classification from mature testicular teratoma.

It is controversial if the rare dermoid cyst of the testis should be classified as a variant of mature teratoma or separately. The spectrum of findings is also ill defined, as is the relationship of dermoid cyst to intratubular germ cell neoplasia of the unclassified type (IGCNU). This study therefore reports the findings in five testicular dermoid cysts that occurred in five patients, 17-42 years of age, who presented with testicular masses. Four lesions consisted of a keratin-filled cyst with a thickened wall, whereas one had islands of "shadow" squamous epithelial cells with superimposed calcification and ossification (pilomatrixoma-like variant). Hair was identified grossly in two cases. On microscopic examination, four tumors had hair follicles with sebaceous glands showing a typical, cutaneous-type orientation to an epidermal surface, although no hair shafts were present in two. In addition, the fibrous wall contained smooth muscle bundles (all tumors) and eccrine or apocrine sweat glands (4 tumors). In some cases there were also glands lined by ciliated epithelium (4 tumors, including the pilomatrixoma-like variant), intestinal mucosa (1 tumor), and bone (2 tumors). There was no cytologic atypia or apparent mitotic activity, and no case had IGCNU in the seminiferous tubules. All patients were clinical stage I and were treated by orchiectomy without adjuvant therapy. All were well on follow-up from 1.5 to 9.5 years later. This study supports that dermoid cyst may have noncutaneous teratomatous elements and that an important criterion for its diagnosis is the absence of IGCNU. It also supports that it should be categorized separately from mature testicular teratoma because of the malignant nature of the latter in postpubertal patients. These observations suggest that there are at least two pathways for testicular teratomas in postpubertal patients: the more common being through IGCNU by differentiation from an invasive malignant germ cell tumor and the less common one, taken by dermoid cyst, by direct transformation from a nonmalignant germ cell.

Primary extrapulmonary sugar tumor (PEST): a report of four cases.

The cell of origin and direction of differentiation of the clear cell tumor of the lung (the so-called sugar tumor) remains enigmatic. Recognition of HMB-45 immunoreactivity and identification of melanosomes have suggested a relationship to angiomyolipoma of kidney or liver and lymphangiomyoma. This has given rise to the concept that clear cell tumors are neoplasms of so-called perivascular epithelioid cells--PEComas. Herein we report the existence of four similar tumors occurring in extrapulmonary sites, one of which had malignant features. The three benign tumors occurred in females ages 9, 20, and 40 years; two were located in the rectum and one in the vulva. The malignant tumor occurred in the inter-atrial cardiac septum of a 29-year-old man. Common histologic features were a richly vascular organoid architecture, tumor cells with clear to pale eosinophilic cytoplasm, abundant glycogen, and immunoreactivity for HMB 45, but not S100, multiple keratin, neuroendocrine, or muscle markers. Benign tumors demonstrated low mitotic activity, no necrosis, and good circumscription; the malignant tumor showed considerable mitotic activity, necrosis, and an infiltrative growth pattern. Ultrastructurally, glycogen was present, mitochondria were abundant, and membrane-bound lamellated bodies consistent with premelanosomes were present in two cases, and equivocal in one. Because these tumors have light microscopic, immunohistochemical, and electron microscopic features similar to pulmonary sugar tumors, we propose the name primary extrapulmonary sugar tumor (PEST) for them. Although most PEST's are probably benign, malignant forms appear to exist. These cases further support the concept of a family of systemic HMB-45 positive tumors that include sugar tumors, angiomyolipoma of kidney or liver, lymphangiomyomas, and clear-cell myomelanocytic tumors of the falciform ligament/ligamentum teres.

Mixed epithelial and stromal tumor of the kidney lacks the genetic alterations of cellular congenital mesoblastic nephroma.

Mixed epithelial and stromal tumor of the kidney is a recently recognized neoplasm that occurs almost exclusively in perimenopausal women. Because it frequently contains areas of smooth muscle in which epithelial structures are embedded, some have concluded that it is the adult form of congenital mesoblastic nephroma. Others have concluded that the morphology and epidemiology of mixed epithelial and stromal tumor indicate that it is unrelated to congenital mesoblastic nephroma. Although the genetic alterations of mixed epithelial and stromal tumor have not been previously elucidated, much is known about the genetic alterations of cellular congenital mesoblastic nephroma. The present study was undertaken to determine if mixed epithelial and stromal tumors have any of the genetic alterations recognized as typical of cellular congenital mesoblastic nephroma. RNA extraction was performed on formalin-fixed, paraffin-embedded tissue from 7 mixed epithelial and stromal tumors followed by reverse-transcription polymerase chain reaction to detect the ETV6-NTRK3 gene fusion. Fluorescent in situ hybridization with centromere-specific probes for chromosomes 8, 11, and 17 was performed to evaluate polyploidy of these chromosomes in 11 cases of mixed epithelial and stromal tumor. None of the mixed epithelial and stromal tumors showed any of these genetic alterations. We conclude that mixed epithelial and stromal tumor of the kidney lacks the genetic alterations typical of cellular congenital mesoblastic nephroma, is unrelated to it, and the appellation "adult mesoblastic nephroma" should not be used for these tumors.

Intrarenal schwannoma: a report of four cases including three cellular variants.

Renal schwannomas are extraordinarily rare neoplasms; only six have been reported, the majority of which occurred in the renal pelvis. We report the clinical and pathologic features of four additional cases. The resected kidney in all patients contained a well-demarcated, yellow-tan, smooth, and bulging intraparenchymal tumor (mean size, 9.7 cm; range, 4 to 16 cm). Microscopically, three cases were classified as cellular schwannomas, and one was a usual-type schwannoma, with degenerative nuclear atypia. By immunohistochemistry, all tumors were strongly S-100 protein positive and negative for pan-cytokeratin, CD57, smooth muscle actin, desmin, and CD34. Epithelial elements were not noted in the tumors, and there was no history of any clinical syndromes in these patients. Analysis of the four cases showed the mean age at presentation to be 47 years (range, 18 to 84 years), with no sex predisposition (two men, two women). Most patients were asymptomatic, and all received a diagnosis of renal cell carcinoma and treated as having such. Recognition and awareness of these rare, benign tumors will assist in the differential diagnosis of spindle cell tumors of the kidney and prevent their misdiagnosis as sarcomatoid carcinomas of the kidney or renal sarcomas. Our study, the largest series to date of renal schwannomas, demonstrates a predilection for the cellular variant in the kidney, documents that these tumors may present in the nonhilar region of the kidney, and provides clinical evidence of their benign biologic behavior.

Mixed epithelial and stromal tumor of the kidney.

We describe the clinicopathologic features of 12 patients with a distinctive tumor of the kidney characterized by a mixture of epithelial and stromal elements that form solid and cystic growth patterns. Similar tumors were reported previously in the literature under various names, including adult mesoblastic nephroma. All but one of the patients were women. The only man had a long history of treatment with lupron and diethylstilbesterol. Seven of the women had histories of long-term oral estrogen use of whom six had undergone total abdominal hysterectomy and bilateral salpingo-oophorectomy several years prior, and the seventh patient had been using oral contraceptives for many years. Another woman had this operation but did not receive any hormone therapy. Ages ranged from 31 to 71 years (mean, 56 yrs). Six patients presented with symptoms, including pain and infections attributable to mass effect, and in six the tumor was detected incidentally. Grossly, the tumors were well-circumscribed (mean size, 6 cm; range, 3-12 cm) and consisted of solid and cystic components, most often in equal proportions but in variable distribution. Microscopically, the spindle cell component ranged in appearance from scar-like fibrous tissue to leiomyoma-like interlacing fascicles; usually there was a mixture of both. More cellular foci reminiscent of ovarian stroma or solitary fibrous tumor were also present. No blastema was present. Epithelial elements (composed of clusters of tubules with variable lining) were scattered amidst the spindle cells, and focally transformed into large cysts lined by cells with abundant pink cytoplasm and a hobnail appearance. Immature epithelial elements typical of Wilms' tumor were not present. Muscle markers (desmin and smooth muscle actin) were positive diffusely and strongly in the spindle cells of all tumors, whereas HMB-45 and CD34 were absent. Estrogen receptors were detected in the nuclei of spindle cells in seven tumors and progesterone receptors in three. The distinctive clinicopathologic characteristics of these lesions warrant their classification as a separate category of kidney tumor. We suggest the descriptive term "mixed epithelial and stromal tumor" for this group until its nature and relationship to other kidney lesions are further clarified. Its preponderance in females with a history of long-term estrogen replacement and the history of long-term sex-steroid use in the only male patient, combined with the frequent content of estrogen and progesterone receptors in the spindle cells, suggest that the hormonal milieu plays a role in the evolution of these tumors. The clinical and pathologic parallels with mucinous cystic tumors of pancreas and liver raise the possibility of a common pathogenetic mechanism that may be linked to the periductal fetal mesenchyme. We think this entity is a benign composite neoplasm in which stroma and epithelium are both integral neoplastic components.

Prognostic factors in prostate cancer. College of American Pathologists Consensus Statement 1999.

BACKGROUND: Under the auspices of the College of American Pathologists, a multidisciplinary group of clinicians, pathologists, and statisticians considered prognostic and predictive factors in prostate cancer and stratified them into categories reflecting the strength of published evidence and taking into account the expert opinions of the Prostate Working Group members. MATERIALS AND METHODS: Factors were ranked according to the previous College of American Pathologists categorical rankings: category I, factors proven to be of prognostic importance and useful in clinical patient management; category II, factors that have been extensively studied biologically and clinically but whose importance remains to be validated in statistically robust studies; and category III, all other factors not sufficiently studied to demonstrate their prognostic value. Factors in categories I and II were considered with respect to variations in methods of analysis, interpretation of findings, reporting of data, and statistical evaluation. For each factor, detailed recommendations for improvement were made. Recommendations were based on the following aims: (1) increasing uniformity and completeness of pathologic evaluation of tumor specimens, (2) enhancing the quality of data collected pertaining to existing prognostic factors, and (3) improving patient care. RESULTS AND CONCLUSIONS: Factors ranked in category I included preoperative serum prostate-specific antigen level, TNM stage grouping, histologic grade as Gleason score, and surgical margin status. Category II factors included tumor volume, histologic type, and DNA ploidy. Factors in category III included perineural invasion, neuroendocrine differentiation, microvessel density, nuclear roundness, chromatin texture, other karyometric factors, proliferation markers, prostate-specific antigen derivatives, and other factors (oncogenes, tumor suppressor genes, apoptosis genes, etc).

Primary malignant melanoma of the urethra: a clinicopathologic analysis of 15 cases.

The clinical and pathologic features of 15 primary urethral melanomas occurring in patients (nine women and six men) age 44 to 96 years (mean age, 73 yrs) are described. In the men the tumor involved the distal urethra. In eight women it involved the distal urethra, usually the meatus; both the distal and proximal urethra were involved in one woman. The tumors were typically polypoid and ranged from 0.8 to 6 cm (mean, 2.6 cm) in maximum dimension. A vertical growth phase was present in all tumors, with a prominent nodular component in seven of them. A radial growth phase was seen in nine tumors. The depth of invasion ranged from 2 to 17 mm. The tumors had diffuse, nested, storiform, or mixed growth patterns. The neoplastic cells typically had abundant eosinophilic cytoplasm, large nuclei with prominent nucleoli, and brisk mitotic activity. Melanin pigment was seen in 12 tumors but was conspicuous in only six. At the time of diagnosis, 13 tumors were confined to the urethra and two patients had lymph node metastasis. Nine patients died of disease 13 to 56 months after initial diagnosis and treatment, and one patient had a local recurrence at 4 years and subsequently died of sepsis 1 year later. Three patients were alive and well at 11 months, 23 months, and 7 years. One patient died at the time of the initial operation, and one died of a ruptured aortic aneurysm at 3 years without evidence of melanoma at autopsy. Primary malignant melanomas of the urethra, one fifth of which are amelanotic, must be included in the differential diagnosis of a number of primary neoplasms that involve the urethra, including transitional cell carcinoma, sarcomatoid carcinoma, and sarcomas. Conventional prognostic factors, such as depth of invasion or tumor stage, do not seem to play as important a role in predicting survival as the mucosal location and the nodular growth present frequently in these tumors.

Sex cord-stromal tumors of the testis with entrapped germ cells: a lesion mimicking unclassified mixed germ cell sex cord-stromal tumors.

The authors describe 10 sex cord-stromal tumors of the testis that incorporated germ cells, thereby mimicking the unclassified type of mixed germ cell sex cord-stromal tumor (MGCSCST). These neoplasms occurred in patients from 3 to 48 years old (mean age, 26 years) who presented with testicular masses. On microscopic examination, nine tumors had a combination of tubular and cord-like arrangements of sex cord cells with transition to spindle-shaped tumor cells. They were diagnosed as either unclassified sex cord-stromal tumors (n = 5) or Sertoli-stromal cell tumors (n = 4). One tumor was a pure Sertoli cell tumor. The admixed germ cells were usually at the periphery and in clusters, but occasionally were in the center or more diffuse. In nine patients the germ cells resembled spermatogonia, having round nuclei with uniform, dusty chromatin and inconspicuous or small nucleoli. None of these cells stained with a variety of markers used for neoplastic germ cells, and in one case in which the non-neoplastic Sertoli cells were strongly reactive for inhibin but the neoplastic Sertoli cells were not, all the germ cells within the tumor occurred adjacent to inhibin-positive Sertoli cells. With static cytophotometry, a diploid deoxyribonucleic acid content was found in these germ cells in the two investigated cases. In one case the germ cells had the morphologic appearance of seminoma cells and they stained positively for the markers of neoplastic germ cells. This case was interpreted as a "collision" tumor between a Sertoli cell tumor and a seminoma. The authors conclude that sex cord-stromal tumors with entrapped germ cells of the testis are more common than unclassified MGCSCSTs--a bona fide testicular example of which has not been seen by any of the authors.

The paratesticular region: histoanatomic and general considerations.

The paratesticular region includes the testicular collecting system, the testicular tunics, and spermatic cord. For the purpose of discussion in this issue, the rete testis is also considered part of the paratestis, although it is principally intratesticular in location. The embryologic origins of the paratesticular components and their detailed anatomic and histologic features are presented to provide a background to better understand the pathologic processes affecting the paratestis. A wide variety of cysts, hyperplasias, neoplasms, and tumor-like conditions may affect the paratesticular region, at times resulting in challenging problems in differential diagnosis. An approach to the paratesticular causes of an intrascrotal mass lesion is presented.

Mesothelial lesions of the paratesticular region.

Mesothelial lesions involving the paratesticular region include mesothelial cysts, reactive mesothelial hyperplasia, adenomatoid tumors, benign cystic mesothelioma, well-differentiated papillary mesothelioma, and malignant mesothelioma. The diagnosis and management of these lesions are often difficult for surgical pathologists, surgeons, and oncologists alike. Mesothelial lesions are relatively uncommon and most benign and malignant tumors present as testicular tumors with no specific findings. A preoperative diagnosis of malignancy is rarely made, and there is no established effective therapy for malignant mesothelioma. This article reviews the clinicopathologic features of paratesticular mesothelial lesions with emphasis in their differential diagnosis and prognosis.