Dermatofibroma (DF) is a common, benign fibrohistiocytic tumor with unknown pathogenesis. There are multiple uncommon histologic variants of DF reported in literature, one of which is hemosiderotic DF. It can variably present as a pigmented papule or nodule commonly located on the lower extremities. Hemosiderotic DF remains to be underreported in the Philippines despite the widely available dermatopathology services in the country.
Human ; dermatofibroma ; histiocytoma, benign fibrous

Objective: To investigate the clinicopathological and cytogenetic features of cryptic COL1A1-PDGFB fusion dermatofibrosarcoma protuberans (CC-DFSP). Methods: Three cases of CC-DFSP diagnosed in West China Hospital, Sichuan University, Chengdu, China from January 2021 to September 2021 were studied. Immunohistochemistry for CD34 and other markers, fluorescence in situ hybridization (FISH) for PDGFB, COL1A1-PDGFB and COL1A1, next-generation sequencing (NGS), reverse-transcriptase polymerase chain reaction (RT-PCR) and Sanger sequencing were performed. Results: There were three cases of CC-DFSP, including two females and one male. The patients were 29, 44 and 32 years old, respectively. The sites were abdominal wall, caruncle and scapula. Microscopically, they were poorly circumscribed. The spindle cells of the tumors infiltrated into the whole dermis or subcutaneous tissues, typically arranging in a storiform pattern. Immunohistochemically, the neoplastic cells exhibited diffuse CD34 expression, but were negative for S-100, SMA, and Myogenin. Loss of H3K27me3 was not observed in the tumor cells. The Ki-67 index was 10%-15%. The 3 cases were all negative for PDGFB rearrangement and COL1A1-PDGFB fusion, whereas showing unbalanced rearrangement for COL1A1. Case 1 showed a COL1A1 (exon 31)-PDGFB (exon 2) fusion using NGS, which was further validated through RT-PCR and Sanger sequencing. All patients underwent extended surgical resection. Except for case 3 with recurrence 2 years after surgical resection, the other 2 cases showed no recurrence or metastasis during the follow-up. Conclusions: FISH has shown its validity for detecting PDGFB rearrangement and COL1A1-PDGFB fusion and widely applied in clinical detection. However, for cases with negative routine FISH screening that were highly suspicious for DFSPs, supplementary NGS or at least COL1A1 break-apart FISH screening could be helpful to identify cryptic COL1A1-PDGFB fusions or other variant fusions.
Female ; Humans ; Male ; Collagen Type I, alpha 1 Chain ; Dermatofibrosarcoma/pathology* ; In Situ Hybridization, Fluorescence ; Oncogene Proteins, Fusion/genetics* ; Proto-Oncogene Proteins c-sis/genetics* ; Skin Neoplasms/pathology* ; Adult

Objective: To investigate the clinicopathological features, immunophenotypes and molecular genetics of EWSR1-SMAD3 positive fibroblastic tumor (ESFT) with an emphasis on differential diagnosis. Methods: The clinicopathological data, immunohistochemical profiles and molecular profiles of 3 ESFT cases diagnosed at the Department of Pathology, Fudan University Shanghai Cancer Center from 2018 to 2021were analyzed. The related literature was also reviewed. Results: There were two males and one female. The patients were 24, 12 and 36 years old, respectively. All three tumors occurred in the subcutis of the foot with the disease duration of 6 months to 2 years. The tumors were presented with a slowly growing mass or nodule, accompanied with pain in 1 patient. The tumors ranged in size from 0.1 to 1.6 cm (mean, 1.0 cm). Microscopically, the tumors were located in the subcutaneous tissue with a nodular or plexiform growth pattern. They were composed of cellular fascicles of bland spindle cells with elongated nuclei and fine chromatin. One of the tumors infiltrated into adjacent adipose tissue. There was no nuclear atypia or mitotic activities. All three tumors showed prominent stromal hyalinization with zonal pattern present in one case. Focal punctate calcification was noted in two cases. The immunohistochemical studies showed that tumor cells were diffusely positive for ERG and negative for CD31 and CD34, with Ki-67 index less than 2%. Fluorescence in situ hybridization on the two tested cases identified EWSR1 gene rearrangement. The next generation sequencing analysis demonstrated EWSR1-SMAD3 fusion in all three cases. During the follow up, one patient developed local recurrence 24 months after the surgery. Conclusions: ESFT is a benign fibroblastic neoplasm and has a predilection for the foot, characterized by ERG immunoreactivity and EWSR1-SMAD3 fusion. Local recurrence might occur when incompletely excised. Familiarity with its clinicopathological features is helpful in distinguishing it from other spindle cell neoplasms that tend to occur at acral sites.
Adult ; Child ; Female ; Humans ; Male ; Biomarkers, Tumor/analysis* ; China ; In Situ Hybridization, Fluorescence ; Neoplasms, Fibrous Tissue/pathology* ; RNA-Binding Protein EWS/genetics* ; Smad3 Protein/genetics* ; Soft Tissue Neoplasms/surgery*

Humans ; Child ; Dermatofibrosarcoma/surgery* ; Skin Neoplasms/surgery* ; Oncogene Proteins, Fusion/genetics*

Fibro-osseous lesions is a class of diseases with obvious similarities in clinical manifestations and pathological features, which has been attracting the attention of clinicians and pathologists. The latest WHO 2022 Classification (5th edition) included six of these diseases (cemento-osseous dysplasia, segmental odontomaxillary dysplasia, fibrous dysplasia, juvenile trabecular ossifying fibroma, psammomatoid ossifying fibroma and familial gigantiform cementoma) in the " fibro-osseous tumours and dysplasias ", and put forward new ideas on the diagnosis and treatment of these diseases. According to the latest WHO 2022 Classification (5th edition), the clinical and pathological features, diagnosis and differential diagnosis of these six diseases were described.
Humans ; Fibroma, Ossifying/pathology* ; Diagnosis, Differential ; Cementoma/pathology* ; Jaw Neoplasms ; Facial Bones

Malignant peripheral nerve sheath tumor (MPNST) is a rare neurogenic malignant tumor. MPNST has aty-pical clinical symptoms and imaging presentations, difficult diagnosis, a high degree of malignancy, and poor prognosis. It usually occurs in the trunk, approximately 20% in the head and neck, and rarely in the mouth. This paper reports a case of MPNST of the tongue. A summary of the clinical features, diagnosis, and treatment of MPNST is presented in combination with a literature review to provide a reference for the diagnosis and treatment of this disease.
Humans ; Nerve Sheath Neoplasms/pathology* ; Neurofibrosarcoma ; Tongue/pathology*

Objective: To investigate the clinicopathological features, immunophenotypes and molecular genetics of fibroma of tendon sheath (FTS). Methods: One hundred and thirty-four cases of FTS or tenosynovial fibroma diagnosed in the Department of Pathology, West China Hospital, Sichuan University, Chengdu, China from January 2008 to April 2019 were selected. The clinical and histologic features of these cases were retrospectively reviewed. Immunohistochemistry, fluorescence in situ hybridization (FISH) and reverse transcription-polymerase chain reaction (RT-PCR) were performed on the above cases. Results: There were a total of 134 cases of FTS, including 67 males and 67 females. The patients' median age was 38 years (ranged from 2 to 85 years). The median tumor size was 1.8 cm (ranged from 0.1 to 6.8 cm). The most common site was the upper extremity (76/134, 57%). Follow-up data was available in 28 cases and there was no detectable recurrence. Classic FTS (114 cases) were well-defined and hypocellular. A few spindle-shaped fibroblasts were scattered in the dense collagenous sclerotic stroma. Characteristically elongated slit-like spaces or thin-walled vessels were observed. Most of cellular FTSs (20 cases) were well-defined and the area with increased cellularity of the spindle cells coexisted with classic FTS. There were occasional mitotic figures, but no atypical mitotic figures. Immunohistochemistry was performed in 8 cases of classic FTS and most cases were positive for SMA (5/8). Immunohistochemistry was also performed in 13 cases of cellular FTS and showed 100% positive rate for SMA. FISH was conducted on 20 cases of cellular FTS and 32 cases of classical FTS. USP6 gene rearrangement was found in 11/20 of cellular FTS. Among 12 cases of CFTS with nodular fasciitis (NF)-like morphological feature, 7 cases showed USP6 gene rearrangement. The rearrangement proportion of USP6 gene in cellular FTS without NF-like morphological features was 4/8. By contrast, 3% (1/32) of the classic FTS showed USP6 gene rearrangement. RT-PCR was performed in those cases with detected USP6 gene rearrangement and sufficient tissue samples for RT-PCR. The MYH9-USP6 fusion gene was detected in 1 case (1/8) of the cellular FTSs, while no target fusion partner was detected in the classic FTS. Conclusions: FTS is a relatively rare benign fibroblastic or myofibroblastic tumor. Our study and recent literature find that some of the classic FTS also show USP6 gene rearrangements, suggesting that classical FTS and cellular FTS are likely to be at different stages of the same disease (spectrum). FISH for USP6 gene rearrangement may be used as an important auxiliary diagnostic tool in distinguishing FTS from other tumors.
Male ; Female ; Humans ; Gene Rearrangement ; In Situ Hybridization, Fluorescence ; Retrospective Studies ; Fibroma/pathology* ; Fasciitis/genetics* ; Ubiquitin Thiolesterase ; Tendons/pathology*

Humans ; Pleura/pathology* ; Solitary Fibrous Tumor, Pleural/pathology* ; Adenocarcinoma of Lung ; Lung Neoplasms ; Pleural Neoplasms/pathology*

Humans ; Fasciitis/pathology* ; Fibroma/pathology* ; Gene Rearrangement ; Proto-Oncogene Proteins/genetics* ; Ubiquitin Thiolesterase

Objective: To investigate the clinicopathological, immunophenotypic, and genetic features of malignant peripheral nerve sheath tumor (MPNST). Methods: Twenty-three cases of MPNST were diagnosed at the Jiangsu Province Hospital (the First Affiliated Hospital of Nanjing Medical University), China, between January 2012 and December 2022 and thus included in the study. EnVision immunostaining and next-generation sequencing (NGS) were used to examine their immunophenotypical characteristics and genomic aberrations, respectively. Results: There were 10 males and 13 females, with an age range of 11 to 79 years (median 36 years), including 14 cases of neurofibromatosis type I-associated MPNST and 9 cases of sporadic MPNST. The tumors were located in extremities (7 cases), trunk (4 cases), neck and shoulder (3 cases), chest cavity (3 cases), paraspinal area (2 cases), abdominal cavity (2 cases), retroperitoneum (1 case), and pelvic cavity (1 case). Morphologically, the tumors were composed of dense spindle cells arranged in fascicles. Periphery neurofibroma-like pattern was found in 73.9% (17/23) of the cases. Under low magnification, alternating hypercellular and hypocellular areas resembled marbled appearance. Under high power, the tumor cell nuclei were irregular, presenting with oval, conical, comma-like, bullet-like or wavy contour. In 7 cases, the tumor cells demonstrated marked cytological pleomorphism and rare giant tumor cells. The mitotic figures were commonly not less than 3/10 HPF, and geographic necrosis was often noted. Immunohistochemically, tumor cells were positive for S-100 (14/23, 60.9%) and SOX10 (11/23, 47.8%). The loss of the CD34-positive fibroblastic network encountered in neurofibromas was observed in 14/17 of the MPNST cases. The loss of H3K27me3 expression was observed in 82.6% (19/23) of the cases. Moreover, SDHA and SDHB losses were presented in one case. NGS revealed that NF1 gene loss of function (germline or somatic) were found in all 5 cases tested. Furthermore, four cases accompanied with somatic mutations of SUZ12 gene and half of them had somatic mutations of TP53 gene, while one case with germline mutation in SDHA gene and somatic mutations in FAT1, BRAF, and KRAS genes. Available clinical follow-up was obtained in 19 cases and ranged from 1 to 67 months. Four patients died of the disease, all of whom had the clinical history of neurofibromatosis type Ⅰ. Conclusions: MPNST is difficult to be differentiated from a variety of spindle cell tumors due to its wide spectrum of histological morphology and complex genetic changes. H3K27me3 is a useful diagnostic marker, while the loss of CD34 positive fibroblastic network can also be a diagnostic feature of MPNST. NF1 gene inactivation mutations and complete loss of PRC2 activity are the common molecular diagnostic features, but other less commonly recurred genomic aberrations might also contribute to the MPNST pathogenesis.
Female ; Male ; Humans ; Child ; Adolescent ; Young Adult ; Adult ; Middle Aged ; Aged ; Neurofibrosarcoma ; Neurofibromatosis 1 ; Histones ; Genes, p53 ; Nerve Sheath Neoplasms