A case of pleural epithelioid sarcoma of proximal type presenting as malignant pleural mesothelioma

SMARCB1/INI1-deficient tumors of adulthood

The SMARCB1/INI1 gene was first discovered in the mid-1990s, and since then it has been revealed that loss of function mutations in this gene result in aggressive rhabdoid tumors. Recently, the term "rhabdoid tumor" has become synonymous with decreased SMARCB1/INI1 expression. When genetic aberrations in the SMARCB1/INI1 gene occur, the result can cause complete loss of expression, decreased expression, and mosaic expression. Although SMARCB1/INI1-deficient tumors are predominantly sarcomas, this is a diverse group of tumors with mixed phenotypes, which can often make the diagnosis challenging. Prognosis for these aggressive tumors is often poor. Moreover, refractory and relapsing progressive disease is common. As a result, accurate and timely diagnosis is imperative. Despite the SMARCB1/INI1 gene itself and its implications in tumorigenesis being discovered over two decades ago, there is a paucity of rhabdoid tumor cases reported in the literature that detail SMARCB1/INI1 expression. Much work remains if we hope to provide additional therapeutic strategies for patients with aggressive SMARCB1/INI1-deficient tumors.

Primary pleural epithelioid sarcoma of the proximal type: a diagnostic and therapeutic challenge

Epithelioid sarcoma (ES) is an uncommon soft tissue neoplasm first described in 1970. It is a unique soft tissue neoplasm of adolescents and younger adults which usually presents as a subcutaneous and deep dermal mass in the distal portions of the extremities. The proximal-type variant of this rare soft tissue neoplasm was only recently reported. The proximal form typically arise in proximal extremities and in the deep parts of pelvis, perineum and genital tract. The proximal type variant has distinct histological characteristics and aggressive clinical course as compared to the distal ES. Inactivation of INI1 has been reported in both distal and proximal variants and can help to make the diagnosis. Furthermore, the proximal variant has a possible association with malignant rhabdoid neoplasm. We describe here a case of primary pleural ES of the proximal type and highlight its diagnostic and therapeutic challenges.

Clinicopathological analysis of myxoid proximal-type epithelioid sarcoma

Proximal-type epithelioid sarcoma (ES) with a diffuse myxoid stroma is rare. Here, we report the case of a 33-year-old man with a perineal mass. Imaging showed the presence of a poorly demarcated 6.9 × 5.3-cm mass in the subcutaneous perineal region. Macroscopic examination showed that the resected tissues were partially necrotic. Histological examination showed that the tumor comprised numerous large or pleomorphic epithelioid cells with large vesicular nuclei and prominent nucleoli. A clear background of necrosis and inflammatory exudates was also present. Immunohistochemical examination showed that the tumor cells were positive for vimentin and CD34 - both of which were expressed throughout the cytoplasm - but typically did not express nuclear INI1 (SMARCB1). Hematoxylin-eosin staining (HE staining) showed that the mucin content of the tumor was approximately 80%. The patient was diagnosed with proximal-type ES with myxoid features. The patient died due to disease progression after 2 months of follow-up and without undergoing further treatment in our department. To our knowledge, only 2 cases of proximal-type ES with diffuse myxoid stroma have been reported. Proximal-type ES is rare, and this is the first case report of proximal ES with myxoid features in the perineal area.

Primary proximal epithelioid sarcoma of the lung successfully treated with pneumonectomy and adjuvant chemotherapy

Primary sarcomas of the lung and proximal epithelial sarcomas (PESs) are extremely rare. Inactivation of INI1 has been found in the majority of epithelioid sarcoma (ES). We report the third known case of a primary PES of the lung along with immunohistochemical data. A 41-year-old man with HIV infection, on highly active antiretroviral therapy, presented with haemoptysis, shortness of breath and progressive weight loss for 2 months. He was eventually diagnosed with stage IIA cT2bN0M0 grade-2 primary PES of the lung. This patient underwent pneumonectomy and adjuvant chemotherapy with ifosfamide and doxorubicin. He remains in remission 36 months since diagnosis. Our case stands to help other clinicians as treatment of such rare cases is often reliant on case reports. We also posit a possible pathogenic mechanism given a history of HIV infection in this patient. The association of INI1 mutation with other atypical sarcomas in patients with HIV infection merits further evaluation.