FDG PET positive benign peripheral Schwannoma

Case contributed by Dr Chris O'Donnell

Presentation

PH of malignant melanoma. Recent PET scan shows an avid mass in left popliteal fossa. For further investigation prior to excision. Histology - benign Schwannoma

Patient Data

Age: 60
Gender: Male

PET scan

Modality: Nuclear medicine

Rounded mass in the left popliteal fossa showing subtle but definite uptake of FDG

Modality: MRI

Large well-defined mass in the politeal fossa intimately related to the common peroneal nerve (arrow) shwoing an internal "spoke wheel" appearance and patchy enhancement following Gd contrast.  Oedema in surrounding soft tissues.

Modality: Ultrasound

Well-defined, lobulated mass with internal "microcystic" appearance and internal blood flow on colour Doppler

Case Discussion

Schwannomas or neurilemomas are reasonly common benign nerve sheath tumours that can affect most if not all peripheral nerves.  They are in general FDG avid and should be included in the differential of mass lesions detected on PET.  There is unfortunately no correlation between avidity and aggressiveness i.e. the presence of marked FDG uptake (high SUV > 6) does not necessarily indicate a malignant nerve cell tumour.

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Case Information

rID: 42974
Case created: 16th Feb 2016
Last edited: 8th Mar 2016
Inclusion in quiz mode: Included

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