Primary peripheral neurolymphomatosis mimicking synovial sarcoma: FDG PETCT to the rescue.

Our understanding of the association between synovial sarcoma and peripheral neurolymphomatosis is limited to a few case reports in literature. Delay in diagnosis or misdiagnosis is possible due to its insidious onset and varied presentation compounded by non-specific imaging findings. Needle biopsy also may not be confirmatory especially, in cases of biphasic sarcoma as in our case, and it may be necessary to proceed to open biopsy. Here, is a case of a non-tender right calf muscle mass, which was reported as biphasic synovial sarcoma by FNAC. Positron emission tomography computed tomography-computed tomography (PETCT) showed right sciatic nerve involvement and multiple infra diaphragmatic lymph nodal lesions. Intensity of (18)F FDG ((18)Flourine labeled fluro de oxy glucose) uptake and the infra diaphragmatic lymph nodal lesions distribution, was more in favour of a lymphoma diagnosis rather than a sarcoma, (which are usually low metabolically active tumors). Thus, this case highlights the usefulness of FDG PETCT in arriving at a diagnosis in the background of indeterminate clinicopathological and radiologic findings.