Introduction :
The DICER1 -tumor predisposition syndrome (OMIM 6012000) is an autosomal dominant disorder with incomplete penetrance and exhibits multiple tumors over time in affected kindreds. 1-6 It is characterized by heterozygous germline mutation in DICER1 gene.4 DICER1 -associated tumors can also be due to biallelic somatic mutations and can be grouped into sarcomas and non-sarcomatous tumors. These comprise a varied spectrum of unrelated benign to malignant tumours, as well as non-neoplastic entities.7-9 DICER1 -associated sarcomas have been reported in literature under a varied list of appellations such as pleuropulmonary blastoma (PPB; the prototype), embryonal rhabdomyosarcoma (ERMS), anaplastic sarcoma of kidney, adenosarcoma, primitive intracranial sarcoma, carcinosarcoma, fibrosarcoma, leiomyosarcoma, primitive neuroectodermal tumour (PNET), mesenchymal chondrosarcoma and more recently PPB-like peritoneal sarcoma.7-9 It is increasingly being recognized that these sarcomas may be morphologically similar enough for a unified terminology - DICER1 -associated sarcoma. 7,10
We present a series of three DICER1 -associated extrapulmonary sarcomas, each of whom presented with a spindle cell sarcoma of primitive morphology and rhabdomyoblastic differentiation on immunohistochemistry and did not respond to conventional rhabdomyosarcoma chemotherapy. We compared the morphology with that of other reported DICER1 -associated sarcomas to identify morphologic clues to guide appropriate molecular testing for diagnosis of these tumours.