Changyoung Yoo

Background/Objectives: Malignant transformation of soft tissue lesions is uncommon but represents a significant diagnostic challenge with substantial clinical consequences. This spectrum encompasses four interrelated processes but biologically distinct processes: (1) true malignant transformation of benign lesions; (2) dedifferentiation of low-grade or intermediate malignancies; (3) secondary malignancy arising in chronic inflammatory or non-neoplastic conditions; and (4) apparent progression related to tumor heterogeneity and sampling error. Although these four entities involve biologically distinct mechanisms, they are grouped under “malignant progression” for conceptual clarity. While this umbrella approach has limitations due to biological heterogeneity, this unified radiologic framework aims to supplement, rather than oversimplify, their distinct biological behaviors. Representative examples include neurofibroma and epidermal inclusion cyst among benign lesions; atypical lipomatous tumor/well-differentiated liposarcoma, dermatofibrosarcoma protuberans, and solitary fibrous tumor among lesions showing dedifferentiation or malignant progression; and chronic inflammatory or scar-related conditions and previously irradiated tissue associated with secondary malignancy. Some lesions that appear to progress during follow-up may represent initial underdiagnosis rather than true biologic progression. Methods: This narrative review summarizes current imaging features, underlying pathologic mechanisms, and clinical risk factors associated with these processes in soft tissue lesions. Particular emphasis is placed on radiologic–pathologic correlation and conditions prone to histopathologic misinterpretation. Results: Imaging red flags—including interval or rapid growth, deep fascial invasion, heterogeneous enhancement, perilesional edema, and necrosis—should raise concern for malignant progression across these categories. However, overlapping imaging features and sampling errors may result in pathologic misdiagnosis and delayed treatment. Particularly, atypical lipomatous tumors are frequently misdiagnosed as simple lipomas, while fibrosarcomas may be erroneously interpreted as aggressive fibromatosis. Advanced imaging and multidisciplinary review may help reduce diagnostic errors. Patients with predisposing factors such as genetic syndromes, chronic inflammation, prior burns, or previous radiation exposure warrant close surveillance. Conclusions: Accurate diagnosis of soft tissue lesions with true malignant transformation, dedifferentiation, or secondary malignancy—as well as recognition of diagnostic pitfalls—is essential for appropriate management. Integrated radiologic–pathologic assessment may help improve diagnostic accuracy and clinical decision-making in soft tissue oncology.

Background/Objectives: Malignant transformation of bone lesions, although rare, poses a major diagnostic and clinical challenge. Common benign lesions (e.g., osteochondroma, enchondroma, fibrous dysplasia, giant cell tumor), non-tumorous conditions (e.g., chronic osteomyelitis, irradiated bone, infarction), and low-grade malignancies (e.g., low-grade osteosarcoma, chondrosarcoma) can evolve into aggressive malignancies through distinct genetic, molecular, and microenvironmental pathways. Recognizing early malignant transformation on imaging is crucial for timely diagnosis and management. Methods: This review synthesizes current imaging characteristics, pathologic mechanisms, and clinical risk factors associated with malignant transformation of benign and low-grade malignancy bone lesions. Results: Atypical imaging findings and inaccurate biopsies can delay diagnosis. Aggressive features—such as cortical destruction, heterogeneous enhancement, and loss of internal matrix—should prompt further pathologic evaluation. Advanced imaging and a multidisciplinary approach with integrated clinicoradiologic–pathologic review are essential to minimize missed diagnoses. Patients with risk factors such as genetic syndromes, prior denosumab therapy, inadequate surgery, or prior radiation therapy require close monitoring or timely intervention. Conclusions: Radiologic–pathologic correlation remains central to distinguishing benign from malignant lesions. This review article emphasizes a comprehensive imaging-pathology overview of benign and low-grade malignancy bone lesions with malignant potential, aiming to improve diagnostic accuracy and outcomes in orthopedic oncology.

Nevus sebaceous (NS) is a common congenital hamartoma of the skin composed predominantly of sebaceous glands. Although most NS are benign skin tumors, malignant transformations have been reported. There is still controversy about the lifetime risk of malignant degeneration and precise surgical criteria. This study reports cases of malignant degeneration and suggests a surgical treatment algorithm. The medical records of patients with basal-cell carcinoma (BCC) arising from NS between January 2001 and January 2021 were retrospectively reviewed. Patient demographics including lesion location, and tumor size were investigated. The symptoms, histological findings before and after excision, complications, and recurrence during 2-year follow-up periods were investigated. Ten patients were identified with BCC arising from NS lesions. All patients were female and the mean age was 52.11 years. All patients complained of sudden morphological changes, the most common type being rapid color changes. Two cases had histological findings that showed a miss-match between punch biopsy and excisional biopsy results. No recurrence was detected 2 years after surgeries in any patients. Cases after third stage, especially in over 40 years who report morphologic changes, should undergo total surgical excision as the first approach, with strong suspicion of malignant degeneration.

Most diffuse gliomas are reported to harbor isocitrate dehydrogenase (IDH) mutations. However, when these mutations are tested in clinical practice, the results are often negative. This study examined the frequency of IDH1 and IDH2 mutations in gliomas classified according to the revised 2016 World Health Organization classification, and investigated their prognostic relevance. We tested 87 gliomas for IDH1 and IDH2 mutations using the peptide nucleic acid clamp method. IDH1 mutations were observed in 42% of diffuse astrocytomas, 23% of anaplastic astrocytomas, all oligodendrogliomas and anaplastic oligodendrogliomas, and 17% of glioblastomas. An IDH2 mutation was identified in one case of diffuse astrocytoma. In the survival analysis of diffuse astrocytic tumors, patients with IDH1/2-wildtype anaplastic astrocytomas tended to have a poor prognosis, similar to that of glioblastomas. IDH2 mutations were infrequent in gliomas. In anaplastic astrocytomas, the frequency of IDH1/2-wildtype was relatively high, and the prognosis of patients with this type of tumor was very similar to that of those with glioblastomas. It may therefore be necessary to reconsider the classification and treatment strategies for IDH1/2-wildtype anaplastic astrocytomas.

Calcifying fibrous tumor (CFT) is a recently recognized rare benign lesion characterized by dense hyalinized collagenous tissue with interspersed spindle cells and a lymphoplasmocytic infiltrate. Calcification is the hallmark of CFT and may present in the form of psammomatous bodies or dystrophic calcifications. CFT of the intestinal tract is uncommon and rectal CFT has never been reported. Recently, we experienced a case of CFT found in the rectum of a 36-year-old man. In this study, we described the characteristic histopathological findings with a review of the relevant literature. Although CFT of the intestinal tract as an intrinsic visceral lesion is unusual and clinically unexpected, CFT should be considered in the differential diagnosis of rectal submucosal tumor.

Background: Histone deacetylase inhibitors are a new class of drugs used in treatment of malignant tumors. Diffuse large B-cell lymphoma (DLBCL) is the most common type of B-cell lymphoma, and it accounts for more than 40% of all B-cell lymphomas. In this study, we aimed to determine the expression patterns of histone deacetylases (HDACs) in DLBCL, to examine whether HDAC expression patterns differ among cases, and to assess whether these findings have clinical significance.