Perineural invasion progressing to leptomeningeal carcinomatosis: Is the absence of peripheral nerves an important sign?

Background

Leptomeningeal carcinomatosis (LMC) is a rare, frequently fatal complication of cranial nerve invasion by a primary cutaneous carcinoma.

Objective

Complete absence of nerve tissue was observed in retrospect in a Mohs surgery case that had subsequently proceeded to LMC. We theorized that the cancer invaded the perineural space and spread contiguously until meeting a point of resistance, in this case the mental foramen. Pressure on the nerve resulted in Wallerian degeneration of the peripheral nerve, causing progressive anesthesia and obscuring the presence of perineural invasion (PNI). Our objective was to find out if this was an isolated phenomenon or an important sign of PNI progressing to LMC.

Methods

We report and describe a case and review similar case reports in the literature.

Results

Twenty-two case reports fit our criteria. In only two cases was carcinomatous PNI reported in initial surgical specimens.

Limitations

There are relatively few similar case reports in the literature. In many reports, histopathologic findings are not detailed enough to be helpful. Absence of peripheral nerves, although inferred, is not specifically stated in any other case report.

Conclusion

The absence of nerve tissue in a Mohs surgery specimen, coupled with signs of cranial nerve involvement, could be important early indicators of PNI progressing to LMC.

Key words: cranial neuropathy, cutaneous squamous cell carcinoma, leptomeningeal carcinomatosis, Mohs surgery, perineural invasion

Abbreviations used: BCC, basal cell carcinoma, C&D, curetting and desiccation, CN, cranial nerve, CNS, central nervous system, CT, computed tomography, LMC, leptomeningeal carcinomatosis, MRI, magnetic resonance imaging, PNI, perineural invasion, SCC, squamous cell carcinoma, V3, mandibular branch of the trigeminal nerve, XRT, radiation therapy