Tumor metastásico en tejido blando a nivel del sacro secundario a carcinoma de células claras de riñón. Reporte de caso / Metastatic tumor in soft tissue at the level of the sacrum secondary toclear cell carcinoma of the kidney. A case report

Introducción. El cáncer de riñón es la undécima neoplasia maligna más común en los Estados Unidos Mexicanos. El carcinoma de células claras de riñón (CCR) es considerado la estirpe más frecuente y representa el 2-3 % de todos los cánceres a nivel mundial. En el contexto de la enfermedad metastásica, por lo general se identifica un tumor renal primario y las metástasis se localizan en pulmón, hueso, hígado, cerebro y, raramente, en tejidos blandos. Los pacientes con metástasis a tejidos blandos no tienen síntomas en las etapas iniciales y generalmente se identifican sólo cuando las lesiones aumentan de tamaño o durante el estudio de la pieza de resección quirúrgica. Caso clínico. Se presenta el caso de una paciente en la séptima década de la vida, con una metástasis en tejidos blandos de la región sacra, de 10 años de evolución posterior a una nefrectomía secundario a CCR. Resultados. Hallazgos clínicos e imagenológicos de un tumor bien delimitado. Se realizó resección quirúrgica de la lesión, bajo anestesia regional, con extirpación completa. Conclusión. Se recomienda que los pacientes con un sitio metastásico resecable y solitario sean llevados a resección quirúrgica con márgenes libres, como fue el caso de nuestra paciente, por su fácil acceso y ser una lesión única. En el CCR, además de su tratamiento quirúrgico inicial, es indispensable una estrecha vigilancia con examen físico e imágenes transversales, para detectar la presencia de metástasis y con ello evitar tratamientos tardíos.

Introduction. Kidney cancer is the eleventh most common malignancy in the United States of Mexico. Carcinoma renal cell (CRC) is considered the most frequent type and represents 2-3% of all cancers worldwide. In the setting of metastatic disease, a primary renal tumor is usually identified, and metastases are located in the lung, bone, liver, brain, and rarely in soft tissue. Patients with soft tissue metastases do not have symptoms in the initial stages and are generally found only when the lesions increase in size or during the study of the surgical resection piece. Clinical case. In this case, we report a female patient in the seventh decade of life with a soft tissue metastasis located in the sacral region, 10 years after a nephrectomy secondary to CRC. Results. Clinical and radiological findings of a well-defined tumor. Surgical resection of the lesion is performed under regional anesthesia with complete excision. Conclusions. It is recommended that patients with a resectable and solitary metastatic site be candidates for surgical resection with free margins, as was the case with our patient due to its easy access and single lesion. In CRC, in addition to its initial surgical treatment, close surveillance with physical examination and cross-sectional images is essential to monitor the presence of metastases and thus avoid late treatments.

SRF-rearranged cellular perivascular myoid tumor: a clinicopathological analysis of two cases / 中华病理学杂志

Objective: To investigate the clinicopathological features, immunophenotype, diagnosis and differential diagnosis of SRF-rearranged cellular perivascular myoid tumor. Methods: Two cases of SRF-rearranged cellular perivascular myoid tumor diagnosed in the Department of Pathology, Fudan University Shanghai Cancer Center from October 2021 to March 2022 were collected. Immunohistochemical staining, fluorescence in-situ hybridization (FISH) and next-generation sequencing (NGS) were performed, and the literature was reviewed. Results: Case 1, a 3-month-old boy presented with a painless tumor of the scalp, measuring about 2 cm in diameter. Case 2, a 3-year-old girl complained with a painless tumor of the knee, measuring approximately 1.5 cm in diameter. Microscopically, the tumor had a clear boundary and showed multinodular growth. The tumor was mainly composed of spindle cells arranged in long intersecting fascicles associated with thin, slit-like or branching ectatic vessels, focally forming hemangiopericytoma-like appearance. The tumor cells were abundant, but there was no obvious atypia. Mitotic figures (3-4/10 HPF) were noted. H-caldesmon and SMA were positive in both cases. Case 1 showed diffuse and strong positivity for Desmin, and focally for CKpan. Ki-67 proliferation index was 20% and 30%, respectively. FISH displayed NCOA2 gene translocation in case 1 and the RELA gene translocation in case 2. NGS detected the SRF-NCOA2 gene fusion in case 1 and the SRF-RELA gene fusion in case 2. Both patients underwent local excisions. During the follow-up of 5-14 months, case 1 had no local recurrence, while case 2 developed local recurrence 1 year post operatively. Conclusions: SRF-rearranged cellular perivascular myoid tumor is a novel variant of perivascular cell tumor, which tends to occur in children and adolescents. The tumor forms a broad morphologic spectrum ranging from a pericytic pattern to a myoid pattern, and include hybrid tumors with a mixture of pericytic and myoid patterns. Due to its diffuse hypercellularity and increased mitotic figures and smooth muscle-like immunophenotype, the tumor is easy to be misdiagnosed as myogenic sarcomas. The tumor usually pursues a benign clinical course and rare cases may locally recur.

Interpretation of histiocytic/dendritic cell neoplasms and stromal-derived neoplasms of lymphoid tissues in the 5th edition of WHO classification of haematolymphoid tumors / 中华病理学杂志

The 5th edition of the World Health Organization classification of hematolymphoid tumors (WHO Blue Book) is soon to be published. Significant revisions have been made in the chapters on histiocytic/dendritic cell neoplasms and stroma-derived neoplasms of lymphoid tissues, leading to the reclassification and renaming of specific diseases. This article provides a concise interpretation and summary of these updates, highlighting the differences from the fourth edition. Pertinent changes from clinical pathological diagnosis to treatment and prognosis are explored, with an emphasis on recent advancements in molecular genetics. Newly introduced disease classifications are discussed, and the section on follicular dendritic cell sarcoma contributed by the author is detailed to assist readers in quickly understanding and assimilating the new classification standards.

Localización atípica de un lipoblastoma en una niña de 5 años / Atypical location of lipoblastoma in a 5-year-old girl

Se informa de un lipoblastoma perineal en una niña de 5 años localizado en el labio mayor derecho. La lesión aumentó gradualmente en 6 meses. En la ecografía y la resonancia magnética (RM), se observó un tumor heterogéneo sólido limitado con componente graso. Tras su extirpación quirúrgica, el estudio anatomopatológico confirmó un lipoblastoma. El lipoblastoma es un tumor mesenquimatoso benigno poco frecuente de la lactancia y la primera infancia. Los síntomas varían en función de la localización; pueden observarse signos de compresión de los órganos adyacentes. Este tipo de tumores inusuales de los tejidos blandos son más frecuentes en menores de 3 años. Los lipoblastomas se localizan predominantemente en las extremidades, pero también pueden encontrarse en la cabeza y el cuello, el tronco, el mediastino, el riñón, el mesenterio, el retroperitoneo y el perineo. Se debe sospechar su presencia en función de los hallazgos de la ecografía y la RM.

We reported a perineal lipoblastoma in a 5-year-old girl located in the right labia mayor. The lesion gradually increased within 6 months. Ultrasound and magnetic resonance imaging (MRI) showed a limited solid heterogenous tumor with fatty component. After it had been surgically removed, the anatomopathological examination confirmed that it was a lipoblastoma. Lipoblastoma is a rare benign mesenchymal tumor of infancy and early childhood. Symptoms vary depending on localization; signs of compression of adjacent organs may be seen. This type of unusual soft tissue tumors occurred most often in under 3 years old. The localization of lipoblastomas is predominantly in the extremities but may be also found in other sites including the head and neck, trunk, mediastinum, kidney, mesentery, retropritoneum and perineum. The suspicion should be considered according to ultrasound and MRI findings.

Tumores vasculares de interesse odontológico: aspectos clínicos e formas de tratamento / Vascular tumors of dental interest: clinical aspects and forms of treatment

Os hemangiomas são neoplasias benignas dos tecidos moles. São lesões caracterizadas pela proliferação de células endoteliais. Objetivos: O objetivo deste trabalho é demonstrar por meio de uma revisão da literatura os principais hemangiomas de interesse odontológico e suas características clínicas e abordagens terapêuticas. Revisão de literatura: O estudo mostrou prevalência de até 6% na população geral, sendo o tumor mais comum na infância. Essas lesões apresentam rápido crescimento pós-natal, que pode levar meses a dois anos em média, mas geralmente após esse período ocorre sua involução. O diagnóstico é comumente baseado nas características clínicas e na história do paciente. É importante entender que o estudo histopatológico pode ser necessário nos casos em que o diagnóstico é incerto, para diferenciá-lo de outras neoplasias graves. Destacam-se as principais complicações relacionadas a lesões, ulcerações e hemorragias, além de infecções secundárias que podem causar alto índice de morbidade. Assim, é fundamental que o dentista reconheça essas patologias e tenha capacidade para tratá-las. Considerações finais: Foi possível observar que os hemangiomas são manifestações vasculares incomuns para o cirurgião-dentista, porém o profissional deve saber diagnosticá-los e tratá-los. Dentre as áreas acometidas, essas lesões são frequentes na cavidade oral e o tratamento consiste em acompanhamento com intervenções conservadoras(AU)

Hemangiomas are benign soft tissue neoplasms. These are lesions characterized by the proliferation of endothelial cells. Objectives: The objective of this work is to demonstrate through a literature review about the main hemangiomas of dental interest and clinical characteristics and therapeutic approaches. Literature review: The study showed a prevalence of up to 6% in the general population, being the most common tumor in childhood. These lesions presents a rapid postnatal growth, which may take months until two years on average, but usually after this period their involution occurs. The diagnosis is commonly based on clinical characteristics and patient's history. It is important to understand that the histopathological study may be necessary in cases that the diagnostic is uncertainty, in order to differentiate it from other serious neoplasms. Main complications related to injuries, ulceration and hemorrhage can be highlighted, in addition to secondary infections that can cause a high rate of morbidity. Thus, it is essential that dentists recognize such pathologies and be able to treat them. Final considerations: Was possible do observe that hemangiomas are uncommon vascular manifestations for the dental surgeon, however, the professional must know to diagnose and treat them. Among the affected areas, these lesions are frequently seen in the oral cavity and the treatment consists of following up with conservative interventions(AU)

Fibromatosis subescapular como causa de escápula alada. Presentación de un caso y revisión bibliográfica / Subscapularis fibromatosis as a cause of winged scapula. Case report and literature review

La escápula alada suele producirse por lesiones neurológicas tanto del nervio espinal como del nervio torácico largo. La aparición a causa de un tumor ventral de la escápula dificulta su diagnóstico inicial. Presentamos el caso de una mujer joven, con limitación para la rotación externa del hombro, sin antecedentes traumáticos conocidos, evolución progresiva e imagen compatible con una lesión de partes blandas dependiente de la aponeurosis del músculo subescapular confirmada por biopsia como un tumor desmoide. Aunque se trata de un tumor benigno y autolimitado, tiene una inquietante alta tasa de recidivas después de la resección, por lo que se dispone de numerosos tratamientos y muchos grupos optan por hacer un seguimiento médico estrecho de los factores pronósticos y las limitaciones funcionales del paciente, con lo que obtienen resultados satisfactorios y, en algunas series, superiores a los del tratamiento quirúrgico. Nivel de Evidencia: IV

Winged scapula is usually caused by neurological injuries to both the spinal nerve and the long thoracic nerve. Its presence as a result of a ventral scapular tumor makes initial diagnosis difficult. We present the case of a young woman with limited external shoulder rotation, no known traumatic history, and images consistent with a soft tissue lesion dependent on subscapular muscle aponeurosis, which was confirmed by biopsy as a desmoid tumor. Although it is a benign, self-limiting tumor, it has an alarmingly high rate of relapse after resection, so many treatments are available, and many teams choose to closely monitor the patient's prognostic factors and functional limitations, obtaining satisfactory outcomes and, in some series, superior to those of surgical treatment. Level of Evidence: IV

Determinación del grado de agresividad tumoral mediante técnicas de inteligencia artificial aplicadas a imágenes de resonancia magnética / Measuring tumor aggressiveness through artificial intelligence

Objetivo: Determinar el grado de agresividad tumoral mediante técnicas de inteligencia artificial utilizando imágenes de resonancia magnética de sarcomas con grado histológico comprobado. Materiales y Métodos: Dos cohortes retrospectivas independientes de pacientes con sarcomas de partes blandas. Para cada paciente de las dos cohortes se adquirieron tres tipos de secuencias de imágenes como indican los protocolos clínicos: potenciadas en T1, en T2 con supresión grasa (T2FS) y STIR. A fin de desarrollar el modelo de inteligencia artificial, se utilizaron 134 imágenes, tanto las de alto grado como las de bajo grado, en T1 y T2 tomando la imagen más representativa del tumor en cualquier corte. Esto se traduce en 36 millones de píxeles que serán analizados por el programa Landing AI. Resultados: La precisión promedio del modelo fue del 84,3% y la sensibilidad, del 73,3%, con un umbral de confianza de 0,66, lo que demuestra inicialmente que se obtuvo un modelo de buena calidad para predecir con imágenes de resonancia magnética el grado de agresividad de un sarcoma de partes blandas antes de la biopsia. Conclusiones: Se presenta un enfoque novedoso para abordar un tipo de enfermedad infrecuente usando técnicas de inteligencia artificial para determinar el grado tumoral en imágenes de resonancia magnética. Según los resultados de nuestro modelo, se lo puede considerar como una segunda opinión experta al realizar los estudios por imágenes antes de la biopsia. Nivel de Evidencia: III

Objective: To determine the degree of tumor aggressiveness by means of artificial intelligence techniques using magnetic resonance images of sarcomas with proven histological grade. Materials and Methods: Two independent cohorts of patients with soft tissue sarcomas (STS) were retrospectively collected. For each patient in the two cohorts, three types of imaging sequences were acquired as indicated by the clinical protocols: T1-weighted (T1), fat-suppressed T2-weighted (FST2) and STIR. For the development of the artificial intelligence model, 134 images were used, both high-grade and low-grade T1 and T2 images, taking the most representative image of the tumor at any slice. This translated into more than 36 million pixels that were analyzed by the Landing AI program. Results: To determine the degree of tumor aggressiveness by means of artificial intelligence techniques using magnetic resonance The model's average accuracy was 84.3%, and its sensitivity was 73.3%, with a confidence threshold of 0.66, indicating that a good quality model was generated for predicting the grade of aggressiveness of an STS prior to biopsy using MRI scans. Conclusions: A novel approach is presented to address a rare pathology using artificial intelligence techniques to determine the tumor grade based on nuclear magnetic resonance images. Based on the results of our model, it can be considered as a second expert opinion when performing imaging studies prior to biopsy. Level of Evidence: III

Radiation-associated sarcomas of bone and soft tissue: a clinicopathological analysis of 46 cases / 中华病理学杂志

Objective: To investigate the clinical, imaging, histological, and molecular features and the differential diagnosis of radiation-associated sarcomas of bone and soft tissue. Methods: Forty-six cases of radiation-associated sarcomas of the bone and soft tissue in Beijing Jishuitan Hospital from January 2010 to January 2022 were retrospectively analyzed; and the imaging, histological features and immunophenotype were examined. Results: There were 33 females and 13 males, aged from 18 to 74 years, with a mean of 52 years. The most common site of radiation-associated sarcomas were the limbs and spine (15 cases), followed by the chest (9 cases). The primary diseases included epithelial tumors (15 breast cancer, 6 cervical cancer, and 5 bowel cancer), hematolymphoid tumors, bone and soft tissue tumors and infectious lesions. The latent period of radiation-associated sarcomas ranged from 2-22 years, with an average of 11.6 years. Histopathologically, the morphology was divergent from the primary tumor. The most common malignant tumor type was undifferentiated sarcoma (22 cases), followed by osteosarcoma (16 cases). The immunophenotype of radiation-related sarcoma was almost the same as the corresponding soft tissue sarcoma. Conclusions: Radiation-induced sarcoma has a wide range of primary tumor types and its imaging, morphology and immunohistochemical features are similar to those of the primary sarcoma of bone and soft tissue. Clinical correlation is often recommended for the differential diagnosis.

A case report of nasopharyngeal inflammatory myofibroblastoma in infant / 临床耳鼻咽喉头颈外科杂志

Inflammatory myofibroblastic tumor （IMT） is a rare mesenchymal soft tissue tumor characterized by borderline or low-grade malignancy. It is rare childhood tumor with an average age of onset of 10 years old. It is even rarer in infants and toddlers, and the etiology and pathogenesis of this tumor are still unclear. The clinical presentation of IMT is non-specific and are related to the location of the tumor. When the tumor compresses adjacent organs, it can cause pain and functional impairment. According to the current literature, IMT is most commonly found in the digestive and respiratory systems, but also occasionally occur in the genitourinary system, head and neck, and limbs. At present, there have been no reports of nasopharyngeal IMT involving nasal cavity of infants and toddlers at home and abroad.This article reports a case of a massive inflammatory myofibroblastic tumor involving the nasal cavity and nasopharynx in an infant. Plasma-assisted minimally invasive surgery was performed through multiple surgical approaches and achieved satisfactory therapeutic results. This case report may provide valuable reference for the treatment of similar diseases.

Advances in the treatment of infantile hemangiomas of the larynx / 临床耳鼻咽喉头颈外科杂志

Infantile hemangiomas are relatively common soft tissue tumors in infants and young children, with a prevalence of about 4.5% in full-term newborns. Subglottic Hemangioma （SGH） is a relatively rare type of hemangioma, and its special location often causes respiratory distress and potentially life-threatening conditions in infants. Therefore, it is necessary for clinicians to make an accurate diagnosis and formulate a detailed treatment plan based on the clinical manifestations, the auxiliary examinations, the medical history and the vital signs evaluation of patients.This review describes the pathophysiological mechanism of infantile hemangioma and provides a detailed discussion on commonly used treatment methods in detail.

EWSR1-SMAD3 positive fibroblastic tumor: a clinicopathological analysis / 中华病理学杂志

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.

Angiolipoma sacro. Reporte de un caso / Sacral angiolipoma. A case report

Fundamento: Los angiolipomas son tumores benignos que se presentan en adultos con una localización, preferentemente, en el espacio epidural posterior torácico. Objetivo: Presentar un caso que debutó con un traumatismo axial lumbosacro donde se evidenció una localización poco común de la lesión y sin relación con las estructuras del canal raquídeo. Presentación del caso: Hombre de 25 años que se cayó y debido a ello se le hizo un traumatismo directo en la región sacrococcígea con dolor y aumento de volumen regional, asociado a parestesias glúteas. Los estudios radiológicos evidenciaron una fractura del cóccix y la presencia de una lesión ubicada en las partes blandas, de aspecto redondeado, homogéneo, sólido, de poco más de 50 mm de diámetro. Se le realizó tratamiento quirúrgico que consistió en coccigectomía subperióstica y exéresis macroscópica de la masa. El estudio histológico concluyó el diagnóstico de un angiolipoma. Conclusiones: Los angiolipomas son tumores raros que tienen características radiológicas peculiares, requieren de alta sospecha clínico-imagenológica para indicar los estudios y el tratamiento. La exéresis total es recomendada para evitar la recurrencia y mejorar el pronóstico.

Background: Angiolipomas are benign tumors that appear in adults with special location in the posterior thoracic epidural position. Objective: To present a case that appeared with a lumbosacral axial trauma where a non-common lesion location was evidenced with no relation among the structures of the spinal canal. Case presentation: 25-year-old man who fell down, consequently suffered a painful direct trauma to the sacrococcygeal region and increased regional volume, associated with gluteal paresthesias. Radiological studies showed a fracture of the coccyx and presence of a lesion located in the soft tissues, with a rounded, homogeneous, solid aspect, a little more than 50 mm in diameter. Surgical treatment consisted of subperiosteal coccygectomy and macroscopic excision of the mass. Histological study concluded the diagnosis of an angiolipoma. Conclusions: Angiolipomas are rare tumors with peculiar radiological features, they require high clinical-imaging suspicion for studies and treatment. Total excision is recommended to avoid recurrence and improve prognosis.

Estudio clínico, radiológico y derivación en tumores musculoesqueléticos / Diagnosis and referral of musculoskeletal tumors

Musculoskeletal tumors are uncommon. However, the true burden of all bone and soft tissue tumors of extremities is underestimated. Usually, the diagnosis of sarcomas is missed or delayed. Therefore, an adequate clinical and radiological assessment, along with the awareness and application of simple guidelines for referral to a specialized center, are of utmost importance. These are critical steps for an appropriate diagnosis and treatment of sarcomas, improving their prognosis.

Angioleiomioma en cavidad oral «una neoplasia rara en un sitio poco común¼. Reporte de un caso y revisión de la literatura / Angioleiomyoma in the oral cavity «a rare neoplasm in an unusual site¼. Case report and literature review

El angioleiomioma (AL) es una neoplasia benigna, bien circunscrita y de crecimiento lento, que representa 5% de las neoplasias de tejidos blandos y cuya etiología es desconocida. Se origina del músculo liso, mayormente de las paredes de los vasos sanguíneos; su localización es más frecuente en extremidades, siendo raros en la región de cabeza y cuello, y más aún en cavidad bucal. Histológicamente la lesión se caracteriza por ser un nódulo bien encapsulado con proliferación de fascículos de músculo liso maduro alrededor de la luz de los vasos sanguíneos, cuyas células suelen ser positivas a marcadores de inmunohistoquímica como alfa actina de músculo liso, desmina, HHF35, miosina, calponina y H-caldesmon. El tratamiento actual es la escisión quirúrgica completa con una tasa de recurrencia prácticamente nula. El objetivo es resaltar la importancia del diagnóstico y el manejo correcto de las lesiones intraorales a través de la presentación de un caso clínico de un leiomioma vascular localizado en región nasolabial, además de hacer la revisión de la literatura correspondiente (AU)

The angioleiomyoma (AL) is a benign neoplasm, well circumscribed and slow growing, that represents 5% of the soft tissue neoplasms, whose etiology is unknown. It originates from smooth muscle, mostly from the walls of blood vessels; regarding its location, it more frequently appears in the extremities, being rare in the head and neck region, and even more so in the oral cavity. Histologically, the lesion is characterized by being a well encapsulated nodule with proliferation of mature smooth muscle bundles around the lumen of the blood vessels, whose cells are usually positive for immunohistochemical markers such as alpha smooth muscle actin, desmin, HHF35, myosin, calponin and H-caldesmon. The current treatment is complete surgical excision having zero recurrence rate. The objective of the following article is to educate on the importance of correct diagnosis and management of intraoral lesions through the presentation of a clinical case of a vascular leiomyoma located in the nasolabial region, in addition to reviewing the corresponding literature (AU)

Osteosarcoma extraesquelético. Presentación de un caso / Extraskeletal osteosarcoma. Case report

El osteosarcoma extraesquelético es un tumor maligno de alto grado que representa menos del 2% de los sarcomas de partes blandas y que afecta principalmente a personas entre la quinta y sexta década de la vida. Típicamente el diagnóstico es tardío, con un período síntomas-diagnóstico extenso, >6 meses en comparación con el del osteosarcoma convencional. Comunicamos el caso de un hombre de 43 años que acudió con una tumoración en la región glútea y el muslo izquierdo de un año de evolución. Luego de estudios complementarios y una biopsia no concluyentes, se procedió a la resección quirúrgica del tumor con márgenes amplios. El estudio histológico de la pieza indicó osteosarcoma extraesquelético. El paciente tuvo una evolución muy buena, sin elementos de recidiva local ni compromiso a distancia luego de 20 meses de seguimiento. Nivel de Evidencia: IV

Extraskeletal osteosarcoma (EOS) is a high-grade malignant tumor that accounts for less than 2% of soft tissue sarcomas and mainly engages people between the fifth and sixth decade of life. It is typically of late diagnosis, with an extensive symptom-diagnosis period greater than 6 months compared to conventional osteosarcoma. We report the case of a 43-year-old patient who presented in our service with a 1-year-old tumor localized in the gluteal and left thigh region. After inconclusive paraclinical studies and biopsy, the tumor was surgically resected with wide margins and diagnosed as EOS after the histological analysis of the piece. The patient showed a very good clinical and paraclinical progression without signs of local or distant recurrence after 20 months of follow-up. Level of Evidence: IV