Perineural Spread of Renal Cell Carcinoma: A Case Illustration with a Proposed Anatomic Mechanism and a Review of the Literature

Introduction

Perineural spread (PNS) is an unusual mechanism of tumor extension and has been typically reported in squamous cell carcinoma, adenocystic carcinoma, and desmoplastic melanoma. Our group has previously demonstrated PNS in rectal, prostate, bladder, and cervical cancer from the primary site along the autonomic nerves to the major somatic nerves and even intradurally. We believe similar principles apply to renal cell carcinoma (RCC) as well, despite the different anatomy.

Case Description

We performed a retrospective search to identify cases of intradural-extramedullary metastases of RCC caused by PNS. Strict anatomic and imaging inclusion criteria were defined: only lesions located between T6 and L3 were included, and PNS as a potential cause had to be supported by imaging evidence. Although 3 cases of spinal intradural metastases were identified, only one met our strict inclusion criteria. A 61-year-old woman developed a late intradural-extramedullary metastasis of RCC 16 years after the original diagnosis that we believe represents an example of visceral organ PNS.

Conclusions

RCC can propagate via PNS from the primary tumor along the autonomic nerves to the aorticorenal, celiac, and mesenteric ganglia and then along the thoracic and lumbar splanchnic nerves to the corresponding spinal nerves and intradurally. We present radiologic evidence together with the review of the literature to support the premise that PNS of RCC not only occurs but goes unrecognized.

Introduction

Perineural spread (PNS) is a recognized mechanism of tumor spread. Prototype malignancies for perineural invasion (PNI) are adenocystic carcinoma,¹ desmotropic melanoma,² or squamous cell carcinoma³ involving the cranial nerves and prostate⁴ and pancreatic cancer⁵ invading the autonomic nerves, but almost every cancer has been shown to extend along the nerves, including other types of pelvic malignancy such as rectal,⁶ cervical,⁷ and bladder cancer.⁸ Although the propensity for nerve involvement is known, the extent is often underestimated. Our group previously demonstrated PNS of various pelvic malignancies to the lumbosacral plexus and beyond to other distant structures such as muscle and bone or intradurally. In pursuit of mapping patterns of PNS across different tumors, we wondered whether similar mechanisms⁹ would apply to renal cell carcinoma (RCC). We identified a case of an intradural metastasis of RCC 16 years after the primary tumor diagnosis, which we believe supports our theory that PNS of RCC occurs and is under-recognized.