Areas Of Dedifferentiation Research Articles

The Use of 18F-FET-PET-MRI in Neuro-Oncology: The Best of Both Worlds-A Narrative Review.

Gliomas are the most frequent primary tumors of the brain. They can be divided into grade II-IV astrocytomas and grade II-III oligodendrogliomas, based on their histomolecular profile. The prognosis and treatment is highly dependent on grade and well-identified prognostic and/or predictive molecular markers. Multi-parametric MRI, including diffusion weighted imaging, perfusion, and MR spectroscopy, showed increasing value in the non-invasive characterization of specific molecular subsets of gliomas. Radiolabeled amino-acid analogues, such as 18F-FET, have also been proven valuable in glioma imaging. These tracers not only contribute in the diagnostic process by detecting areas of dedifferentiation in diffuse gliomas, but this technique is also valuable in the follow-up of gliomas, as it can differentiate pseudo-progression from real tumor progression. Since multi-parametric MRI and 18F-FET PET are complementary imaging techniques, there may be a synergistic role for PET-MRI imaging in the neuro-oncological imaging of primary brain tumors. This could be of value for both primary staging, as well as during treatment and follow-up.

Paratesticular liposarcoma: the clinicopathological features of nineteen cases

Objective: To investigate the clinicopathological features and differential diagnoses of paratesticular liposarcoma. Methods: The cases were collected from 2012-2020, from the archives of the Department of Pathology, Peking University Third Hospital, with diagnosis confirmed by histology, immunostaining and FISH tests. Results: Totally 19 patients were enrolled (including 11 in-hospital patients and 8 consultant cases). The patients aged 37-84 years (mean 57 years). The preoperative clinical diagnoses were spermatic cord/inguinal masses (nine patients), scrotal masses (seven patients), and inguinal hernia (three patients). Six lesions recurred after local resection, including one case extending from pelvic liposarcoma. Histologically, there were 10 cases of well-differentiated liposarcoma (WDLPS) and nine cases of dedifferentiated liposarcoma (DDLPS). WDLPSs mostly showed the combined features of lipoma-like, inflammatory and sclerosing subtypes (six patients); the other four WDLPSs had pure lipoma-like subtype features. DDLPSs were low-grade (three patients) or high-grade (six patients), with the morphology resembling myxofibrosarcoma, inflammatory myofibroblastoma, spindle cell sarcoma, pleomorphic undifferentiated sarcoma and pleomorphic liposarcoma. Intense inflammatory cells infiltration was commonly observed in five WDLPSs and two DDLPSs. Ossification was observed in three tumors. Immunohistochemically, the tumors were positive for MDM2 (8/10) and CDK4 (10/10), which were expressed in lipo-differentiating cells, spindle cells in WDLPS, and in dediffferentiated components. S-100 was only expressed by lipocytes (10/10). CD34 expression was positive and diffuse in the stromal cells of WDLPSs and focal or diffuse in dedifferentiated areas (10/10). FISH tests with an MDM2 gene probe were positive (12/12). Conclusions: Paratesticular liposarcoma may be overlooked by both clinicians and pathologists. WDLPS and DDLPS predominate, showing various histologic divergences. The presence of amplification of the 12q14-q15 region (containing the MDM2 and CDK4 genes) is helpful for making the correct diagnosis.

Dedifferentiated Liposarcoma With Meningothelial-Like Whorls: Five Additional Cases and Review of the Literature.

Background. Diagnosis of dedifferentiated liposarcoma (DDL) can sometimes be challenging due to a wide variety of histological features. "Meningothelial-like" whorl is an uncommon histological feature of DDL, which is also observed in neural tumors and follicular dendritic cell sarcoma. This feature is frequently associated with metaplastic bone formation. We conducted this study to describe the clinicopathological features of DDL with meningothelial-like whorls that would aid in establishing accurate diagnosis. Material and Methods. Microscopic glass slides of 5 cases of DDL with meningothelial-like whorls, diagnosed between January 2010 and December 2019, were reviewed. Results. Paratesticular region was the most common site. Whorls occupied 10% to 75% of tumor area and ranged in size from <0.1 cm to >2 cm. In 1 case, these whorls coalesced to form large areas of dedifferentiation. The cells forming whorls were spindle to epithelioid shaped and lacked significant nuclear pleomorphism and increased mitoses. Metaplastic bone formation was observed in 4 cases and cartilage formation in 3 cases. p16 and α-smooth muscle actin (α-SMA) immunohistochemical stains were positive in 2 cases, when performed. MDM2 gene amplification was observed in all cases by fluorescence in situ hybridization technique. These tumors showed aggressive behavior, similar to that of DDL without meningothelial-like whorls. Two patients died, 1 developed recurrence, 1 presented as recurrent tumor, and 1 developed metastasis. Conclusion. Meningothelial-like whorls in DDL most likely represent an early stage of dedifferentiation. Presence of well-differentiated liposarcoma areas, metaplastic bone formation, positive expressions for p16 and α-SMA immunohistochemical stains, and MDM2 gene amplification are useful diagnostic clues. These tumors have the potential to behave aggressively.

Dedifferentiated soft tissue leiomyosarcoma with heterologous osteosarcoma component: case report and review of the literature

BackgroundSoft tissue dedifferentiated leiomyosarcoma with heterologous osteosarcomatous component is an extremely rare entity described in only few cases in the literature.Case presentationWe report the case of a 65-year-old male patient who, after initial inadequate surgery of a tumor of the left forearm, developed local recurrence that was treated with neoadjuvant chemotherapy, surgery and postoperative radiation therapy. Histologically the tumor showed an abrupt separation of two different patterns. One component consisted of interlacing fascicles of spindle cells with cigar-shaped nuclei strongly positive for smooth muscle actin, desmin and H-caldesmon. The other component consisted of a high-grade pleomorphic sarcoma with osteoid and chondroid matrix production, which positive for SATB2. Thus, a final diagnosis of dedifferentiated leiomyosarcoma was rendered. Fifteen months after treatment, the patient presented further local and distant relapse with pulmonary metastases and died 23 months after the first presentation.Discussion and conclusionsDedifferentiated leiomyosarcoma is a highly malignant neoplasm with a poor outcome. Extensive sampling of soft tissue leiomyosarcomas is recommended to detect possible dedifferentiated areas as they represent a crucial prognostic parameter.

59. Dedifferentiated solitary fibrous tumour arising from the bladder: A case report

Background: Solitary fibrous tumour (SFT) is a rare mesenchymal tumour of fibroblastic differentiation. They most commonly arise in the pleura, but have a wide anatomical distribution. Conventional SFTs are circumscribed, spindle cell neoplasms with characteristic histomorphology including patternless architecture, dense collagen and prominent haemangiopericytoma-like ‘staghorn’ vessels. Conventional SFTs express CD34, Bcl2 and STAT6, but are negative for S100, keratin and desmin. Molecular profiling has shown consistent 12q chromosomal abnormality resulting in NAB2-STAT6 fusion. The NAB2-STAT6 gene fusion product is reliably identified on STAT6 immunohistochemistry, which has proven both a highly sensitive and specific marker for SFTs. Most SFTs are clinically benign, however up to 15% may show features of malignancy including increased mitoses (>4 per 10 HPF), necrosis and infiltrative margins. In addition, areas of dedifferentiation may occur, characterised by sharply demarcated areas of hypercellularity and pleomorphism with loss of morphological features of conventional SFT. Dedifferentiated areas may lose the typical immunohistochemical profile of conventional SFT, including loss of CD34 and STAT6. Aim: To report a case of dedifferentiated SFT in the bladder and review the current literature. Method: A 39-year-old male presented with one month history of urinary frequency and abdominal pain. CT and MRI showed a large heterogenous necrotic mass in the posterior bladder wall. An en bloc tumour resection and cystoprostatectomy was performed. Results: Macroscopic examination showed a 15 cm circumscribed tumour arising from the superior bladder. Microscopy revealed a spindle cell tumour arising from the bladder muscularis propria with areas of conventional SFT adjacent to vast areas of dedifferentiation with malignant features including hypercellularity, pleomorphism, increased mitoses (40 per 10 HPF) and necrosis. Immunohistochemistry showed positive staining for STAT6, CD34 and Bcl2 in both conventional and dedifferentiated areas. Conclusion: This is a unique case of a dedifferentiated SFT of the bladder in a young patient.

A rare femoral tumor in a young patient.

Parosteal osteosarcoma is a low-grade, bone-forming neoplasm that arises on the surface of bone. It accounts for about 4% of all osteosarcomas. An 18-year-old male patient with no particular past medical history, consulted for a painless mass in the right thigh that had appeared at the age of 17 years and progressively increased in volume. The physical examination revealed a 6 cm mass at its largest above the right popliteal fossa with knee flexion slightly limited. The X-ray revealed a well-limited mass in the lower third of the femur that was dense and attached to the metaphyseal cortex by a wide base. Histological examination of the biopsy specimen established the diagnosis of parosteal osteosarcoma. The patient underwent wide resection of the femoral tumor (A) preceded by a course of first-line chemotherapy. Histological examination showed a malignant mesenchymal proliferation, moderately cellular, made up of long, linear and eosinophilic material, sometimes calcified with no osteoblastic cells in the periphery (B). The tumor cells were spindle-shaped, with little eosinophilic cytoplasm and a long or ovoid, hyperchromatic, and moderately atypical nucleus. Mitoses were rare. There were no areas of dedifferentiation. Postoperative course was uneventful. During the one-year follow-up period, there was no recurrence or metastasis of the tumor. Parosteal osteosarcoma is characterized by its insidious growth and favorable prognosis. It rarely leads to metastasis. Its treatment is mainly surgical.

Mixed Adenoneuroendocrine Carcinoma: Is It a Collision Tumor or a Dedifferentiated Carcinoma?

Abstract Mixed adenoneuroendocrine carcinoma (MANEC) of the gastrointestinal tract is uncommon with about 100 cases reported involving esophagus, stomach, colon, rectum, and biliary tree. The aggressive behavior of these tumors is usually dictated by the high-grade neuroendocrine carcinoma (NEC) component, which raises the possibility that these may represent areas of dedifferentiation. We here report an 88-year-old male presenting with rectal bleeding. Colonoscopy identified a fungating, villous, and partially circumferential cecal mass. Biopsy revealed tubular adenoma with focal high-grade dysplasia. However, excision was recommended given the impression of a mass. A right hemicolectomy revealed an 8.7-cm friable and ulcerated mass in the cecum. Initially, eight sections (one per cm) of the tumor were examined and revealed intramucosal adenocarcinoma. However, one of the lymph nodes was replaced by a high-grade poorly differentiated tumor, immunophenotypically consistent with NEC. In search for a primary, the rest of the mass was submitted and subsequent histologic examination revealed areas of transition from villous adenoma to intramucosal and muscle invasive adenocarcinoma in addition to deeply invasive NEC showing marked cytological atypia, brisk mitotic activity (Ki-67 &gt;90%), and lymphovascular invasion. Three lymph nodes had metastatic adenocarcinoma and NEC along with several tumor deposits. Following an uneventful postoperative course, the patient received adjuvant chemotherapy. Our case recapitulates the classic description of MANEC where NEC is usually associated with a differentiated adenocarcinoma, commonly arising from an adenoma. The currently proposed pathogenesis is a collision tumor (previously known as mixed exocrine/endocrine carcinomas). However, we propose viewing MANEC as one tumor rather than two colliding tumors utilizing the concept of dedifferentiation, which has been extensively studied in the GYN literature. In a prior study, we found neuroendocrine expression in 41% of undifferentiated endometrial carcinomas. We therefore propose revisiting larger case series of MANEC with this concept in mind.

Natural history of well-differentiated liposarcoma of the extremity compared to patients treated with surgery

BackgroundPatients with well-differentiated liposarcoma (WDLPS) of the extremity are mostly treated surgically, thereby possibly inducing severe morbidities. Despite the excellent prognosis, the natural history is barely studied. The aim of this study was to evaluate the natural history of extremity WDLPS by evaluating the outcome of patients treated with active surveillance (AS), who thereby exhibited the natural history of extremity WDLPS, and of patients treated surgically. MethodsA large retrospective database of patients with extremity WDLPS was assessed to evaluate treatment, dedifferentiation and disease-specific survival. Lastly, our experience with patients treated with AS was explored. ResultsDistant metastases (5/191 patients, 2.6%) were mainly seen after a dedifferentiated local recurrence. Death of disease occurred in 4/191 patients (2.1%); two patients died from metastatic disease (although not pathologically proven), two patients died of treatment-related complications. In our center, 24 patients are treated with AS. Time of AS varied from 0.1 to 8.9 years (median 1.8). Four patients eventually underwent surgery after a period of AS (range 14–52 months) because of symptoms and/or tumor growth. No areas of dedifferentiation were found in these resection specimens. The other patients are still under active surveillance. ConclusionSince surgical treatment might induce morbidity and even mortality, there might be overtreatment of these patients. Evaluation of the natural history of extremity WDLPS showed that AS could be a reasonable option for selected patients. Prospective studies in patients with extremity WDLPS are needed to assess the safety of AS as a treatment option.

A dedifferentiated solitary fibrous tumor of the parotid gland: a case report with Cytopathologic findings and review of the literature

BackgroundSolitary fibrous tumor (SFT) is a ubiquitous mesenchymal neoplasm but it rarely occurs in the parotid gland. The histological features are variable, with the majority having spindle cell morphology and non-specific branching (staghorn) ecstatic vascular pattern. SFT ranges from benign to overtly malignant. Dedifferentiation within SFTs represents an abrupt transition from a well-differentiated component to a high-grade area, the latter most often including poorly differentiated epithelioid/round cell or high-grade spindle cell morphology. To the best of our knowledge, dedifferentiated SFT in the parotid gland has not been previously reported.Case presentationA 33-year-old woman presented with a soft tissue tumor in the right parotid gland that had been present for 6 months. Fine needle aspiration (FNA) cytology indicated epithelioid morphology in the dedifferentiated component of the tumor, along with metachromatic myxoid matrix. The tumor was initially interpreted as a salivary gland neoplasm of uncertain malignant potential (SUMP).Right partial parotidectomy was performed, and microscopic examination of the resected specimen revealed a malignant spindle cell tumor with a central epithelioid/anaplastic component. The tumor cells were diffusely positive for CD34, STAT-6 and FLI-1, and negative for pan-cytokeratin, CAM5.2, p63, S100 protein, CD31, SMA, and calponin.ERG and Ki67 immunostaining showed an accentuated nuclear staining pattern in the central dedifferentiated area. There was no overexpression of p53 or p16. The patient is currently undergoing regular follow-up and is 11 months postresection with no evidence of recurrence or distant metastasis.ConclusionsUnlike the typical spindle cell morphology of conventional SFTs, malignant SFTs can show areas of dedifferentiation mimicking an epithelial neoplasm. FNA of dedifferentiated SFTs of the parotid gland may show, a combination of atypical epithelioid cells and metachromatic myxoid/collagenous matrix, which is a less emphasized cytological feature of SFT and may lead to misdiagnosis as a more common parotid gland epithelial neoplasm.

Radiation and Its Impact on Local Recurrence in Extremity and Trunk Well-Differentiated Liposarcomas

Patients with well-differentiated liposarcomas (WDLPS) of the extremity and trunk are treated primarily with surgical resection, with radiation used for a number of anecdotal reasons, including large size and positive margins. In this study, we evaluate the appropriate role for radiation in these tumors. A retrospective chart review of patients with extremity and trunk soft tissue liposarcomas referred to a free-standing cancer center from January 1995 to December 2011 was performed. One hundred eighty-three patients with extremity and trunk soft tissue WDLPS were identified: 61 per cent were female, median age was 60 years (range, 19-84 years) and 2 per cent had a focal area of dedifferentiation, margin status was positive in 57 per cent. Fourteen per cent of patients received radiation. Fifty patients developed recurrent disease; 28 per cent of these received radiation. Median time to recurrence was 18 years (range, 0.7-22 years). Of the 50 patients who recurred, 14 (28%) received radiation. Radiation was associated with decreased second recurrence when administered for recurrent disease (P = 0.03). On multivariable analysis, tumor size ≤ 10 cm (P = 0.014) and anatomically difficult area of resection (P = 0.008) were predictive of increased risk of recurrence. Older age (P = 0.02), dedifferentiated liposarcomas (P < 0.001), and difficult area of resection (P = 0.02) were associated with the administration of radiotherapy. Administration of radiation therapy was not associated with decreased time to recurrence in WDLPS overall; however, it should be considered in patients with recurrent disease.

Primary ameloblastic carcinoma of maxilla with extensive squamous differentiation areas of dedifferentiation: report of a case

Primary ameloblastic carcinoma of maxilla with extensive squamous differentiation areas of dedifferentiation: report of a case

Clinical outcome of dedifferentiated liposarcoma in the extremities: A retrospective case series of 7 patients

Wide resection is the generally recommended surgical treatment for dedifferentiated liposarcoma (DDLPS) in the extremities. However, it may be appropriate to distinguish the surgical margin of low-grade atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDLPS) area from the high-grade dedifferentiated area, because the low- and high-grade areas can be clearly separated, both radiologically and histologically. This study re-evaluated the details of surgical margin of DDLPS in the extremities, and aimed to investigate the optimal surgical margin and the usefulness of adjuvant therapy for DDLPS in the extremities. Seven patients diagnosed with DDLPS in the extremities and treated between 1995 and 2013 were analyzed. The use of adjuvant therapy before and after surgery was assessed, and the surgical margins for the ALT/WDLPS and dedifferentiated areas were re-evaluated by using the specimens resected at surgery. Subsequently, the recurrence rates, metastatic rates, and oncological outcomes were examined. Four and three patients had wide (adequate wide margin, n=3; inadequate wide margin, n=1) and marginal margins for the dedifferentiated area, respectively, while three and four patients had wide (adequate wide margin, n=2; inadequate wide margin, n=1) and marginal margins for the ALT/WDLPS area, respectively. Postoperative radiotherapy was performed in three patients with an inadequate wide margin or a marginal margin for the dedifferentiated area. No patient had local recurrence. Distant metastases occurred in two patients. These patients died of their disease. The other five patients were disease-free. The ALT/WDLPS and dedifferentiated areas in the tumor margin may be better to be considered separately in determining the appropriate resection extent for DDLPS in the extremities. Postoperative radiotherapy may provide good local control for cases with a narrow surgical margin.

Breaking dogma for future therapy using stem cell - Where we have reached?

Breaking dogma for future therapy using stem cell - Where we have reached?

Complete remission of a reccurrent mesenteric liposarcoma with rare histological features following the administration of trabectedin

The present study describes a rare case of a mesenteric liposarcoma that resulted in a complete remission (CR) following treatment with trabectedin (Yondelis®). The patient presented with abdominal pain and fever. An abdominal mass was identified that corresponded to a mixed-type high-grade mesenteric liposarcoma with wide areas of necrosis, areas of dedifferentiation and features of a leiomyosarcoma. Three months after the removal of the first mass, the patient underwent a second laparotomy, followed by treatment with doxorubicin and ifosfamide. Subsequently, the patient was started on therapy with trabectedin and a CR was noted following only four cycles of therapy. The best responses that are reported in the literature for cases of liposarcoma treated with trabectedin are mostly for liposarcomas of the myxoid/round cell type and are mainly partial responses. In the present study, trabectedin was used for the treatment of a mesenteric liposarcoma of mixed morphological features and a CR was achieved.

P16 IMMUNOHISTOCHEMISTRY AS A MARKER TO DISTINGUISH BETWEEN ATYPICAL LIPOMATOUS TUMOUR/WELL-DIFFERENTIATED LIPOSARCOMA AND BENIGN ADIPOCYTIC LESIONS

Introduction Atypical lipomatous tumour (ALT)/well-differentiated liposarcoma (WDL) is the most common subtype of liposarcoma. There are marked similarities between normal fat, lipomas and ALT/WDL, making the histological diagnosis of ALT/WDL challenging. In this study we compared the expression of p16 in specimens of ALT/WDL to its expression in other adipocytic tumours and normal adipose tissue to determine whether it is a useful ancilliary tool to distinguish between benign and malignant adipocytic tumours. Methods Thirty liposarcomas, including four with areas of dedifferentiation, 30 lipomas, 26 unusual adipocytic tumours and 16 specimens of normal adipose tissue were included in the study. Immunohistochemistry for p16 was performed on all the specimens. p16 expression was reported as 1+ positive, 2+ positive, 3+ positive and negative. Results Twenty of the 30 specimens of ALT/WDL were 3+ positive, four were 2+ positive and one was 1+ positive. Five specimens were negative, of which four were needle biopsies. All the lipomas and normal adipose tissue were negative. None of the unusual adipocytic lesions were 3+ positive. p16 positivity was significantly more common in ALT/WDL than in the other three groups (p < 0.0001). Conclusions Our findings support the use of p16 immunohistochemistry as a useful marker to distinguish between benign and malignant adipocytic lesions.

Chondrosarcoma of the tongue: A case report and a review of the literature

Chondrosarcoma of the head and neck is uncommon and reported to constitute between 1% to 12% of all chondrosarcoma cases.1, 2, 3 Extraskeletal chondrosarcoma of the tongue is an extremely rare type of neoplasm with only three previously reported cases. The underlying origin of chondrosarcoma arising in the tongue is controversial. We describe a case of a low-grade chondrosarcoma arising in the base of the tongue of a 54-year-old woman with a central area of dedifferentiation. The patient was treated with complete surgical resection with no evidence of recurrence at 1 year follow-up.

De novo malignant solitary fibrous tumor of the kidney

The kidney is a relatively infrequent site for solitary fibrous tumor (SFT). Among the previously reported cases, only two cases of malignant renal SFT developing via dedifferentiation from a pre-existing benign SFT have been reported. Here we reported a case of de novo malignant renal SFT clinically diagnosed as renal cell carcinoma in a 50-year-old woman. The tumor was circumscribed but unencapsulated and showed obvious hemorrhagic necrosis. Microscopically, the tumor was composed of patternless sheets of alternating hypercellular and hypocellular areas of spindle cells displaying mild to moderate nuclear atypia, frequent mitoses up to 8 per 10 high power fields, and a 20% Ki-67 proliferative index. Immunohistochemical studies revealed reactivity for CD34, CD99 and vimentin, with no staining for all other markers, confirming the diagnosis of SFT. No areas of dedifferentiation were seen after extensive sampling. Based on the pathologic and immunohistochemical features, a diagnosis of de novo malignant renal SFT was warranted. Our report expands the spectrum of malignant progression in renal SFTs. Even though this patient has been disease-free for 30 months, long-term follow-up is still mandatory.

Mediastinal liposarcoma of mixed type in childhood: A report of a case with unusual histologic features

We hereby report the occurrence of mediastinal liposarcoma in a 11-year-old female child. Dyspnea and wheezing of long-standing duration were the presenting complaints and a preoperative biopsy failed to yield the diagnosis. Histologic examination revealed heterogeneous areas with well-differentiated liposarcoma-like areas, areas resembling myxoid liposarcoma, and areas of dedifferentiation. Osteosarcomatous foci and whorled areas reminiscent of meningioma were identified in the dedifferentiated areas. Liposarcomas in the mediastinum are extremely rare tumors of childhood and the present case showed unusual histologic features. Complete surgical excision with clear surgical margins remains the primary modality of treatment, although chemotherapy and radiotherapy have been tried.

Dedifferentiated chordoma

Dedifferentiated chordoma is a rare and aggressive variant of the conventional tumour in which an area undergoes transformation to a high-grade lesion, typically fibrous histiocytoma, fibrosarcoma, and rarely, osteosarcoma or rhabdomyosarcoma. The dedifferentiated component dictates overall survival, with smaller areas of dedifferentiation carrying a more favourable prognosis. Although it is more commonly diagnosed in recurrences and following radiotherapy, there have been a few reports of spontaneous development. We describe four such cases, which were diagnosed de novo following primary excision, and discuss the associated clinical and radiological features.

Dedifferentiated high-grade osteosarcoma originating from low-grade central osteosarcoma of the fibula

Low grade central osteosarcoma is a distinct, rare low grade malignant neoplasm characterized histologically by a spindle cell proliferation associated with trabecular bone formation. This tumor usually carries a good prognosis. However, it has the potential to recur, dedifferentiate, and metastasize subsequent to surgical treatment. In extremely rare occasions, LGCOS presents with areas of dedifferentiation upon initial patient evaluation. In this report we describe one such case affecting the fibula of a 39-year-old female, presenting with pain. Initial biopsy demonstrated a high-grade osteosarcoma. No areas of LGCOS were seen histologically. Following biopsy the patient received 3 months of chemotherapy at a different institution. However, the patient continued to exhibit symptoms. X-rays indicated a very aggressive tumor in the diaphysis of the proximal fibula, MRI revealed soft tissue involvement. The tumor and surrounding soft-tissues were excised en bloc at our institution. Microscopically, the lesion consisted of high-grade osteosarcoma as well as an underlying LGCOS that involved the cortex and medullary cavity of the fibula. The two histological components of the tumor were sharply delineated from one another. No chemotherapy effect was appreciated histologically or clinically. Eight months following the surgery, the patient died from lung metastases. This is the third documented case of dedifferentiated LGCOS at initial presentation. This case reveals that the low-grade component was also evident on preoperative radiographs.