IgG4-related disease with subcutaneous involvement and the associated diagnostic challenges with MRI.

IgG4-related disease is a rare fibroinflammatory disorder characterized by the infiltration of IgG4-rich plasma cells. Herein, we report a case of IgG4-related disease of the subcutaneous tissue with atypical MRI findings and difficulties in the histopathological examination using needle biopsy. Based on the clinical presentation and MRI findings, the patient was diagnosed with a benign myxoid or cystic tumor. Additionally, histopathological findings from a needle biopsy suggested a myxoma. Therefore, the correct diagnosis of IgG4-related disease was not made preoperatively. The resected specimens confirmed IgG4-related disease with an IgG4/IgG ratio > 80%. Previous reports have shown that the MRI findings of IgG4-related disease mimic both malignancy and inflammation; surprisingly, the features of subcutaneous IgG-related disease, including tail sign, unclear border, and heterogeneous enhancement, were similar to those found in sarcoma. Therefore, histopathological findings are needed for a correct diagnosis. Furthermore, careful examination is essential because the neoplasm and inflammation may overlap with IgG4-related disease, and needle biopsy is not fully reflective of the tumor. As is highlighted in the present case, IgG4-related disease is often misdiagnosed; therefore, clinicians should adequately recognize that even if the histopathological findings in biopsy were consistent with those observed in the MRI, misdiagnosis may occur.

Comment on Manole et al. Primary Pericardial Synovial Sarcoma: A Case Report and Literature Review. Diagnostics 2022, 12, 158.

With great interest, we read the article by Manole et al [...].

Case report: Characteristics and nature of primary cardiac synovial sarcoma.

Primary malignant cardiac tumors rarely occur, and cardiac synovial sarcoma (SS) is especially rare among such tumors. Herein, we present the case of a 35-year-old female with primary cardiac SS treated with surgery, chemotherapy, and radiotherapy. She presented with chest symptoms and underwent imaging examinations. A cardiac tumor was suspected, and an open biopsy was performed. The pathological findings suggested cardiac SS. Next, we performed a resection, and the tumors persisted at a macroscopic level. Immunohistochemistry was negative for SS18-SSX and positive for the SSX C-terminus and cytokeratin CAM5.2, a reduction of SMARCB1/INI1 was observed, and fluorescence in situ hybridization showed positive SS18 split staining. Owing to the FNCLCC grade 3 tumor and R2 margins, adjuvant chemotherapy with ifosfamide, doxorubicin, and radiotherapy was initiated, and the patient was diagnosed with cardiac SS. The differences in patients with cardiac SS compared with general SS include male predominance, larger tumor size, and poorer prognosis. Pathological findings of immunohistochemistry and fluorescence in situ hybridization were found to be more reliable than imaging findings for a correct diagnosis. Additionally, because incomplete resection is frequently performed, adjuvant therapy, including chemotherapy and radiation therapy, may be performed. The findings indicate that multiple therapies, including surgery, chemotherapy, and radiotherapy, are essential treatment strategies for improving the prognosis of patients with cardiac SS.

Indolent Multinodular Synovial Sarcoma of Peripheral Nerves Mimicking Schwannoma: A Case Report and Literature Review.

BACKGROUND/AIM: Most cases of synovial sarcoma (SS) are aggressive and large-sized; only few show indolent behavior, having a small size. Nerves are rare sites of SS occurrence. An atypical case of SS can lead to its misdiagnosis as a benign tumor and delay its treatment. CASE REPORT: Here, we report a case of primary SS of indolent multinodular synovial sarcoma of peripheral nerves. Considering the clinical and imaging findings at the first visit, we suspected a benign tumor and continued careful follow-up. Three years later, marginal resection was performed and SS was suspected. We then performed an additional wide resection using a free flap. Histopathologically, the proximal tumor showed a diffuse proliferation of spindle cells without pleomorphism, whereas the distal tumor showed a similar histology with more hypercellularity. Additional wide-resection specimens showed remnant tumors derived from the peripheral nerve. Immunohistochemistry (IHC) showed positive staining for SS18:SSX and SSX in both tumors and fluorescence in situ hybridization showed positive staining for the SS18 split in both tumors. Finally, SS of the peripheral nerve was diagnosed. Owing to FNCLCC grade 2 tumor and tumor size, adjuvant chemotherapy was not performed. CONCLUSION: In cases of SS or other sarcomas with atypical clinical courses, with imaging findings mimicking benign tumors, we recommend marginal resection along with pathological examination for correct diagnosis.

Primary Synovial Sarcoma of the Bone: A Case Report and Literature Review.

BACKGROUND/AIM: Synovial sarcoma (SS), a spindle cell sarcoma, typically occurs in the soft tissues of the extremities and rarely develops in the bones as a primary tumor. To our knowledge, no case of SS in the metacarpal bone has been reported. CASE REPORT: We report a case of primary SS of the metacarpal bone. Considering the clinical and imaging findings, SS was difficult to diagnose; therefore, we performed an open biopsy. Next, we performed a wide resection following the management guidelines for SS of the soft tissue. Immunohistochemistry (IHC) showed positive staining for SS18:SSX and SSX, and fluorescence in situ hybridization showed positive staining for the SS18 split. Owing to FNCLCC grade 3 tumor and the R1 margin, adjuvant chemotherapy with ifosfamide and doxorubicin was initiated. Finally, SS of the bone was diagnosed. Furthermore, we reviewed a total of 37 published cases of primary bone SS, including our case. Age and sex were almost the same in all cases of bone SS, and the most frequent site was the long bone in the lower extremity. CONCLUSION: IHC for SS18::SSX and SSX antibodies are beneficial for diagnosing general SS and SS of the bone. Moreover, SS of the bone should be considered in the differential diagnosis of spindle cell sarcomas of the bone. Wide resection and chemotherapy are recommended as current treatment strategies, although further studies are required regarding treatment validity.

Case Report: Extraskeletal osteosarcoma with preceding myositis ossificans.

Extraskeletal osteosarcoma (EO) is a soft tissue sarcoma characterized by the production of bone matrix by neoplastic cells. Benign osteoid in EO, leading to a diagnostic dilemma, is rarely encountered. Herein, for the first time, we present a case with cytogenetically confirmed EO combined with or preceding myositis ossificans (MO). A 21-year-old man had a mildly painful swelling in his left knee. Imaging studies demonstrated a 39-mm mass with peripheral mineralization and cystic change on the posterolateral side of the left fibular head. He was clinically suspected of having either MO or a malignancy, such that wide resection was performed. Macroscopically, the mass was grayish to brown. In the cut section, multiple cystic lesions in addition to solid components were noted. Histopathologically, the solid components demonstrated diffuse proliferation of pleomorphic tumor cells with osteoclast-like giant cells. The malignant tumor cells formed osteoid. In the periphery, the mass was benign, showing mature bone tissue and focally non-malignant woven bone with fibroblasts, compatible with zonation. Fluorescence in situ hybridization (FISH) demonstrated split signals of the USP6 gene. These findings suggested EO with preceding MO. Although the pathogenesis remains to be elucidated, the observed USP6 rearrangement might contribute to both the diagnosis of EO with preceding MO and an understanding of the underlying histopathology.

Case report: Atypical spindle cell/pleomorphic lipomatous tumor masquerading as a myxoid liposarcoma or intramuscular myxoma.

Atypical spindle cell/pleomorphic lipomatous tumors (ASPLTs) were recently categorized as benign lipomatous tumors. However, accurate and complete preoperative diagnosis of ASPLTs may be difficult. Furthermore, diagnosis based on magnetic resonance imaging (MRI) findings is uncertain because of the varying ratios of the fat component within the tumor. Here, we report a case of ASPLT masquerading as a myxoid tumor. Although MRI findings were consistent with a myxoid liposarcoma, needle biopsy findings suggested a myxoma, and we performed marginal resection. Histopathological findings revealed infiltrating spindle cells with atypia. In addition, immunohistochemistry (IHC) showed positive staining for CD34 and heterogeneous retinoblastoma deficiency, and fluorescence in situ hybridization (FISH) showed no amplification of mouse double minute 2 homolog and no rearrangement of FUS or EWSR1. When MRI and histopathological findings suggest a myxoid tumor, IHC and FISH should be considered and performed for a precise and accurate diagnosis.

Spindle Cell Lipoma with Ossification Mimicking Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma: A Case Report.

Although spindle cell lipoma (SCL) is a subtype of lipoma, the characteristics of SCL are observed in both lipomatous and non-lipomatous tumors. In this article, we present a case of SCL with ossification mimicking atypical lipomatous tumors/well-differentiated liposarcomas (ALTs/WDLs). Considering the findings of magnetic resonance imaging and needle biopsy, which exhibited ALTs/WDLs, marginal resection was performed. Histopathological findings demonstrated mature adipocytes and spindle cells without atypia and no malignant osteoid tissue in the ossified region. In addition, immunohistochemistry (IHC) showed positive staining for CD34, heterogeneous retinoblastoma protein deficiency, and negative staining for mouse double minute 2 homolog (MDM2) and cyclin-dependent kinase. Fluorescence in-situ hybridization showed negative amplification of MDM2. The final diagnosis of the tumor was established using IHC as an extremely rare SCL with ossification.