[Histological, immunohistochemical and molecular study of a paratesticular dedifferentiated liposarcoma with inflammatory myofibroblastic tumor-like features]. / Liposarcoma desdiferenciado paratesticular simulando un tumor miofibroblástico inflamatorio. Estudio histológico, inmunohistoquímico y molecular.

We report the histological, immunohistochemical, and molecular findings of a dedifferentiated liposarcoma with inflammatory myofibroblastic tumor-like features occurring in the paratesticular region. Histologically, the dedifferentiated component closely resembled an inflammatory myofibroblastic tumor. The neoplastic cells were positive for smooth muscle actin with focal CD56, CD99, Bcl2 and EMA expression. WT1, calretinin, myogenin, CK(AE1/AE3), desmin, H-caldesmon, CD34, ALK, CKIT, DOG1, MUC4 and STAT6 were negative. MDM2 showed diffuse and strong nuclear positivity in neoplastic cells and fluorescence in situ hybridization (FISH) revealed amplified MDM2 (high level) but no SYT rearrangement. Although a lipomatous component was evident macroscopically, well-differentiated liposarcomatous components were not evident in the section examined. Dedifferentiated liposarcoma can have prominent inflammatory myofibroblastic tumor-like features. Pathologists should be aware of this histological variant in order to avoid misdiagnosing dedifferentiated liposarcoma as inflammatory myofibroblastic tumor or other spindle cell tumors which have different behavioral patterns and treatment requirements.

Liposarcoma desdiferenciado paratesticular simulando un tumor miofibroblástico inflamatorio. Estudio histológico, inmunohistoquímico y molecular / Histological, immunohistochemical and molecular study of a paratesticular dedifferentiated liposarcoma with inflammatory myofibroblastic tumor-like features

Se presenta un estudio histológico, inmunohistoquímico (IHQ) y molecular de un liposarcoma desdiferenciado paratesticular remitido a nuestro centro, con hallazgos histológicos similares a un tumor miofibroblástico inflamatorio. Las células tumorales fueron positivas para actina músculo liso (AML) y focalmente positivas para CD56, CD99, Bcl2 y EMA. La expresión de WT1, calretinina, miogenina, CK(AE1/AE3), desmina, H-caldesmona, CD34, ALK, CKIT, DOG1, MUC4 y STAT6 fue negativa. MDM2 mostró positividad nuclear intensa y difusa por IHQ y alto nivel de amplificación génica mediante hibridación fluorescente in situ (FISH). La FISH no reveló reordenamiento del gen SYT. En el estudio histológico del corte remitido no encontramos evidencias de componente liposarcomatoso bien diferenciado, aunque el aspecto macroscópico de la pieza lo sugería. El liposarcoma desdiferenciado puede presentar hallazgos histológicos que recuerdan a un tumor miofibroblástico inflamatorio y que expanden el espectro histológico de esta variante de liposarcoma. El conocimiento de la existencia de esta variante de liposarcoma es de crucial importancia para no confundirla con otras neoplasias que, aunque histológicamente similares, difieren en la evolución clínica y/o tratamiento.(AU)

We report the histological, immunohistochemical, and molecular findings of a dedifferentiated liposarcoma with inflammatory myofibroblastic tumor-like features occurring in the paratesticular region. Histologically, the dedifferentiated component closely resembled an inflammatory myofibroblastic tumor. The neoplastic cells were positive for smooth muscle actin with focal CD56, CD99, Bcl2 and EMA expression. WT1, calretinin, myogenin, CK(AE1/AE3), desmin, H-caldesmon, CD34, ALK, CKIT, DOG1, MUC4 and STAT6 were negative. MDM2 showed diffuse and strong nuclear positivity in neoplastic cells and fluorescence in situ hybridization (FISH) revealed amplified MDM2 (high level) but no SYT rearrangement. Although a lipomatous component was evident macroscopically, well-differentiated liposarcomatous components were not evident in the section examined. Dedifferentiated liposarcoma can have prominent inflammatory myofibroblastic tumor-like features. Pathologists should be aware of this histological variant in order to avoid misdiagnosing dedifferentiated liposarcoma as inflammatory myofibroblastic tumor or other spindle cell tumors which have different behavioral patterns and treatment requirements.(AU)

Sarcoma de Ewing/PNET simulador de neoplasia primaria de glándula tiroides / Ewing sarcoma/PNET simulating primary thyroid gland neoplasm

Caso clínico: Los autores presentan un sarcoma de partesblandas cervicales que por su forma de presentación clínica,localización yuxtatiroidea y aspecto histológico simulabaun tumor maligno de glándula tiroides. Resultados:Aunque la histología podía ser compatible con varias formasde carcinoma tiroideo, especialmente con un carcinomamedular, los resultados del estudio inmunohistoquímico ylas alteraciones moleculares del gen EWS mediante FISHen parafina correspondieron a un tumor maligno de célulasredondas de estirpe mesenquimal, concordante con sarcomade Ewing/ PNET. Conclusión: Este caso, de gran dificultaddiagnóstica, sirve para recordar que en el diagnóstico diferencialde tumores tiroideos pobremente diferenciadoshemos de considerar la posibilidad de afectación secundariadel mismo por tumores de estructuras vecinas, ya que lossarcomas primarios de la glándula tiroides son muy infrecuentesy en su mayoría corresponden a formas sarcomatoidesde carcinomas tiroideos (AU)

Case report:We report a case of cervical soft tissue sarcomasimulating primary malignant thyroid neoplasm dueto its location, histopathology and clinical presentation.Results: Although histopathology was consistent with severalforms of thyroid carcinoma, most of all, medullary carcinoma,immunohistochemical analysis and moleculargenetic studies on EWS gene, using FISH on paraffinembeddedtissue, yielded the diagnosis of mesenquimalmalignant round cell tumor consistent with Ewing’s sarcoma/PNET. Conclusion: The message of this difficult case isthat differential diagnosis of poorly differenciated thyroidtumors must include the possibility of secondary involvementfrom neighbouring cervical structures because primarythyroid sarcomas are much less frequent than sarcomatoidvariants of primary thyroid carcinomas (AU)