| Abstract|| |
Paratesticular/scrotal and inguinal canal mass lesions in elderly patients may pose a diagnostic challenge to both the surgeon as well as the pathologist. In most cases, these represent hernial sacs with their contents, and true neoplasms like lipomas, rhabdomyosarcomas, and fibrous pseudotumors are infrequent. Malignant mesotheliomas arising from the tunica layers are rare cause of inguinal and paratesticular tumors. Herein, we report a case of an elderly patient who presented with an inguinal hernia which pathologically had features of deciduoid malignant mesothelioma.
Keywords: Deciduoid, inguinal, mesothelioma, tunica vaginalis
|How to cite this article:|
Ahmed S, Menon S, Desai S. Epithelioid malignant mesothelioma of tunica vaginalis with deciduoid features: An unusual malignancy clinically masquerading an inguinal hernia. Indian J Pathol Microbiol 2012;55:89-91
|How to cite this URL:|
Ahmed S, Menon S, Desai S. Epithelioid malignant mesothelioma of tunica vaginalis with deciduoid features: An unusual malignancy clinically masquerading an inguinal hernia. Indian J Pathol Microbiol [serial online] 2012 [cited 2014 Nov 28];55:89-91. Available from: http://www.ijpmonline.org/text.asp?2012/55/1/89/94868
| Introduction|| |
Malignant mesothelioma is an uncommon tumor arising in body cavities lined by mesothelium, most of them occurring in pleura and peritoneum. Tunica vaginalis, a layer of reflected peritoneum, has been a very rare site of these aggressive neoplasms with fewer than 100 cases reported in the world literature. Because of its nonspecific symptoms, wide age distribution, and absence of tumor markers, a preoperative diagnosis is difficult.  However, a longstanding history of exposure to asbestos, hydrocele, or trauma can aid in making a presumptive diagnosis in some cases. ,,, Interestingly, few cases of mesothelioma pathologically show prominent decidual changes, the reasons for which are still unknown. Ustun et al. have cited 45 such cases in English literature with a single case reported in spermatic cord.
We report an extremely rare case of epithelioid malignant mesothelioma with deciduoid features arising in relation to tunica vaginalis which clinically presented as an inguinal hernia.
| Case Report|| |
A 78-year-old male presented with the complaint of painful swelling in the right inguino-scrotal region. Suspecting it to be a case of irreducible inguinal hernia with a possible risk of strangulation, excision of hernial sac and herniorraphy was planned as an emergency measure. On surgical exploration, a soft to firm mass was seen arising from the spermatic cord and adjoining soft tissue with no intraperitoneal extension. The surgeon excised the mass partially due to unexpected findings intraoperatively. Grossly, the mass was firm, irregular, and measured 6 × 1.5 × 0.7 cm with smooth creamish cut surface. The tissue blocks were sent to our institute for pathological examination. Microscopically, the tumor revealed fibro-adipose tissue infiltrated and cordoned by malignant appearing cells. These cells contained eccentrically placed moderately pleomorphic nuclei with abundant and pale eosinophilic cytoplasm resembling a decidual reaction. These neoplastic cells expressed Calretinin, HBME-1, epithelial membrane antigen (EMA), and P53 and were immunonegative for desmin [Figure 1]. A final diagnosis of epithelioid malignant mesothelioma with focal deciduoid change arising from tunica vaginalis was rendered.
|Figure 1: Microscopic examination of epitheloid mesothelioma with deciduoid features. (a and b) The tumor cells are seen involving and lining the adipose tissue with confluent sheeting pattern (HandE, ×100). (c) The malignant cells have abundant cytoplasm with defined cytoplasmic borders resembling decidua (HandE, ×200). (d) The tumor cells showing immunoreactivity to calretinin and epithelial membrane antigen (inset) (Indirect Immunoperoxidase ×200, inset ×100)|
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Following the diagnosis, the patient was then re-investigated for any residual disease and nodal involvement. A whole body positron emission tomography (PET) scan was performed which showed increased uptake in the right inguino-scrotal region. No obvious lymphadenopathy or mass lesion arising elsewhere was seen. A right high inguinal orchidectomy along with nodal dissection was performed as a definitive completion surgery. The surgical specimen consisted of testis, spermatic cord with adjoining soft tissue and skin measuring 15 × 8.5 × 3 cm in the entirety. On serial sectioning, a diffuse firm white tumor measuring 4.5 × 1.5 × 1 cm was identified involving the spermatic cord [Figure 2]. The testis measuring 5 × 3.5 × 2.5 showed thickened tunica layer; however, on serial sectioning, the testicular parenchyma and epididymis appeared grossly unremarkable. The lymph nodes dissected were grossly uninvolved. Histologically, the tumor had similar morphology as the previous resection, although tubulopapillary areas, decidual change, and epithelioid histology were more pronounced in the second resection. Immunohistochemical profile was similar to the previous excision specimen with MIB 1 labeling index of 10-15 % in the highest proliferating areas. Lymphovascular tumor emboli were seen. Tumor did not involve the vas deferens, testicular parenchyma, or epididymis. No lymph nodal metastasis was seen microscopically. The patient is on close follow-up and has not shown any residual disease / recurrence or any metastatic foci in the last 6 months.
|Figure 2: Resected gross specimen of radical orchidectomy following a diagnosis of epitheloid mesothelioma. The left-hand panel shows the thickened cord structures (arrow) and right-hand panel shows the cut sections demonstrating the gray white tumor involving the soft tissue of spermatic cord (arrow)|
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| Discussion|| |
Mesotheliomas are tumors arising from the serosal membranes of the coelomic cavities. The tunica vaginalis formed by outpouching of the abdominal peritoneum has been one of the uncommon sites (less than 1% of all mesotheliomas).  Malignant deciduoid mesothelioma (MDM) as a new entity was named by Nascimento et al. in their description of a peritoneal lesion in a young woman. Although MDM has clinical and histological differences with the conventional mesothelioma, it is still not identified as a distinct variant.
Empirically described to occur in peritoneum of young females, MDM has been, of late, reported to occur in pleura and in elderly patients. Most of the patients belong to an elderly age group as explained by a long latency period (10-40 years) after asbestos exposure.  In our case, the patient did not give a history of exposure to asbestos, trauma, or hydrocele.
Malignant mesotheliomas are classified into three histological types: epithelioid, sarcomatoid, and biphasic. Paratesticular mesotheliomas are usually epithelioid in type (~75% of cases), with the remainder exhibiting a biphasic pattern. , Deciduoid change in a paratesticular mesothelioma is an extremely rare occurrence with only few illustrations in literature. 
Deciduoid areas classically show large polygonal cells with prominent cell borders, plenty of eosinophilic glassy cytoplasm, and round vesicular nuclei often containing prominent nucleoli. Morphological features of deciduoid mesothelioma are often difficult to differentiate from reactive mesothelial proliferation.  Although in MDM the cells are larger, the nuclear cytoplasmic ratio is not increased as in reactive mesothelial cells. The nuclear chromatin has coarser and more granular appearance than the benign reactive mesothelial cells; in addition, the nucleoli and cytoplasm of the cells were more prominent and plentiful, respectively. Features like ciliated cell borders, fenestrations, and mitosis are not of diagnostic value for differentiating benign mesothelial cells from malignant ones. Even though most of these findings are based upon peritoneal tumors, our findings in this paratesticular location were not so different. Another close differential seen in females is extreme decidual reactions, also known as pseudotumoral deciduosis. These lesions can be ruled out by lack of prominent cellular atypia as seen in MDM. ,
Immunohistochemistry is an important adjunct to the diagnosis of malignant mesothelioma. Deciduoid mesotheliomas have a similar immunohistochemical profile to usual pleural and peritoneal mesotheliomas, with majority of the tumors expressing cytokeratin, vimentin, EMA, and calretinin. Majority of the metastatic carcinomas, especially arising from lung and prostate, can be ruled out easily based on immunoexpression. Furthermore, cytokeratin reactivity is strongly positive in mesothelioma, which helps in differentiating it from psedotumoral deciduosis. , The present deciduoid mesothelioma strongly expressed the mesothelial markers.
Radical orchidectomy is the preferred mode of treatment in localized disease. Adjuvant chemotherapy and radiotherapy, either alone or in combination, had been tried in advanced tumor with variable results. With very few cases reported in literature, the exact behavior and treatment response of these testicular decidual mesotheliomas needs to be elucidated with further studies. ,, Malignant mesothelioma of the tunica vaginalis is a locally aggressive tumor, with invasion of subtunical connective tissue and the testis reported in up to 34% of cases at diagnosis.  Tumor recurrences are not uncommon, with more than 60% patients presenting within the first 2 years. Tumors confined to tunica vaginalis have shown survival up to 10 years. Once the disease has metastasized, the survival becomes poor and is similar to the tumor of pleural and peritoneal origin. Deciduoid change in mesotheliomas has shown relatively poor survival rate with almost 68% of the patients dying within 1 year following the start of treatment.  In our case, adverse prognostic factors like vas deferens involvement and lymph nodal metastasis were absent and the tumor is expected to behave favorably. The patient is under close follow-up and has not shown any recurrence / residual disease in the last 6 months. A recent study has identified certain genetic abnormalities in pleural deciduoid mesotheliomas, the most frequent being chromosomal gains at 1p, 12q, 17, 8q, 19, and 20 and losses at 13q, 6q, and 9p. Survival was found to be longer in those patients who presented a smaller number of losses (≤2) in the tumorous chromosomes with the mean survival being 29.5 months. 
In conclusion, we have elucidated a rare case of epithelioid malignant mesothelioma with deciduoid features, which, although rare, must be included in the differential diagnosis of inguinal canal and paratesticular masses, especially in elderly individuals.
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Department of Pathology, 8th Floor, Annexe Building, Tata Memorial Hospital, Parel, Mumbai - 400 012, Maharashtra
[Figure 1], [Figure 2]