[Well-differentiated/dedifferentiated liposarcoma associated with myxoid-like morphology: a clinicopathological and molecular genetic characteristics analysis of 34 cases].

Objective: To investigate the clinicopathological and molecular genetic characteristics of well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS) with myxoid-like morphology, and to distinguish them from myxofibrosarcoma (MFS) with similar morphology. Methods: Twenty-nine cases of myxoid-like liposarcoma and 5 cases of MFS were collected from Henan Provincial People's Hospital, Zhengzhou, China and the First Medical Center of PLA General Hospital, Beijing, China from January 2015 to March 2023. Relevant markers were detected using immunohistochemistry and fluorescence in situ hybridization (FISH). The literature was also reviewed. Results: There were 24 males and 10 females, with ages ranging from 41 to 73 years. The tumor sites included retroperitoneum (n=17), abdomen (n=9), lower limbs (n=5), scrotum (n=1), upper limb (n=1) and axilla (n=1). WDLPS was commonly seen as lipomatoid type (12 cases), while the dedifferentiated components of DDLPS included low-grade (13 cases) and high-grade (2 cases) morphology, with low-high grade myxofibrosarcoma, dermatofibrosarcoma protuberans, and low-grade fibrosarcoma structures. Twenty-nine liposarcomas had various proportions of myxoid-like morphology, while 16 showed various degrees of tumor necrosis. The myxoid-like component showed myxoid pleomorphic liposarcoma (MLPS)-like morphology, lobulated growth, characteristic slender, ramified capillary network,"chicken claw-like"morphology, mucus-rich stroma and lung edema-like morphology. Tumor cells were spindle and oval, with many variable vacuolar lipoblasts. MDM2 gene amplification was detected using FISH and present in all tested cases (29/29). DDIT3 break-apart mutation was not detected, but its cluster amplification was present (24/29). Among the MFS cases, one showed cluster amplification (1/5), but no cases showed break-apart or amplification of MDM2 gene. Conclusions: WDLPS/DDLPS with myxoid-like morphology is most commonly seen in the retroperitoneum and abdominal cavity and mostly harbors DDIT3 break-apart probe amplification, while this amplification is not specific to liposarcoma. For core biopsy specimens or very rare tumors in the limbs, when histology has mucinous stroma and MLPS-like morphology, misdiagnosis of MLPS or other non-lipomatous neoplasms with myxoid morphology should be avoided.

[Clinicopathological analysis of adult hepatic mesenchymal hamartoma].

Objective: To explore the clinicopathological and molecular genetic features of adult hepatic mesenchymal hamartoma (MHL). Methods: A total of five confirmed adult MHL cases diagnosed at the Pathology Department of the First Medical Center of the People's Liberation Army General Hospital between 2009 and 2022 were collected. Histomorphological observation and immunohistochemical staining were conducted. Gene detection was performed by next-generation sequencing. Results: Among the five cases, four were male and one was female, aged 46-67 years, with an average age of 56.2 years. The maximum diameter was 5.3-13.5cm, and the average diameter was 9.2cm. Tumors were generally cystic, solid, or mixed cystic-solid. Histopathologically, in four out of five cases of MHL, malignant transformation occurred, of which three cases were malignantly transformed into undifferentiated embryonal sarcoma and one case was malignantly transformed into a malignant solitary fibrous tumor. NAB2-STAT6 gene rearrangements were identified. Conclusion: Adult MHL is a rare kind of tumor with malignant potential, and it is difficult to diagnose with preoperative imaging examinations. A fine-needle biopsy is rarely used for diagnosis, but surgical resection of symptomatic or enlarged lesions is recommended to rule out the possibility of malignancy and further diagnosis. Genetic testing results revealed the complex genetic alterations in MHL, and it was found that adult MHL can malignantly transform into malignant solitary fibrous tumors. We believe that genome-wide analysis is necessary to determine the unique molecular characteristics of MHL and identify potential targets for therapeutic intervention.