Patient with an NF-1 and large (20-cm) mass along left flank above pelvis. Please define the margins of the plexiform neurofibroma on his left flank/back. Multiple markers placed along the left back/flank denote the patient's mass. Deep to the markers, there is a heterogeneous, poorly-marginated infiltrative mass within the subcutaneous fat which extends deeper to involve the left quadratus lumborum muscle. The subcutaneous portion of the mass is approximately 16 x 4 x 10 cm (transverse x AP x craniocaudal), it's inferior margin situated at approximately the level of the iliac crest, and it's medial margin just left of midline. The superior margin of the subcutaneous component lies at approximately level of L3, but the intramuscular component extends more superiorly to the level of L1, yielding an overall craniocaudal dimension of approximately 16cm. On T1-weighted images the mass has components isointense to both fat and muscle. The majority of the mass is hyperintense to muscle on fat-saturated T2-weighted images. Smaller, better defined nodular components are noted in the mass which have low T1-weighted and high T2-weighted signal. There is a tubular flow void within the mass, indicating a prominent vessel, that courses toward the lumbar vascular plexus. This mass may represent a plexiform/diffuse neurofibroma although could possibly represent a venous malformation.Multiple smaller masses with predominantly high signal intensity on T2-weighted images, some of which have a target appearance, are seen in the subcutaneous tissue and musculature compatible with nerve sheath tumors. Another approximately 1.5-2 cm lesion below the level of the iliac bifurcation with high T2 weighted signal also likely represents a nerve sheath tumor or perhaps a lymph node. Additional neurofibromas are seen arising from the sacral nerve roots. There is also a subcentimeter round focus of signal abnormality within the right ilium along the sacroiliac joint which is nonspecific but may simply represent a cartilaginous rest.
Findings compatible with neurofibromatosis as described above. The heterogeneous, infiltrative left flank mass, as described above, may either represent a plexiform/diffuse neurofibroma or perhaps a venous malformation and extends anteriorly to involve the quadratus lumborum. Other findings as above.