Dermatopathology

Nerve Sheath Myxoma

Nerve sheath myxoma is a rare benign tumor mostly encountered on the extremities in adults. Rarely it can present intracranially, arise in the spinal canal or in the oral cavity. Tumor cells are spindled or oval, bland, grow in nodules and are set in a myxoid stroma.

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Slide 1: 40 year-old woman with a 4th finger lesion. The biopsy comprises multiple lobules of spindled cells distended in a very striking mucinous matrix. The lobules are sharply demarcated from the background hyalinized stroma. They extend to lie in intimate apposition to the epidermis the latter exhibiting focal attenuation.

Slide 2: In examining the lobules the cells are remarkable for their spindled and epithelioid appearance.

Slide 3: The dominant cell populace is more spindled whereby the nuclei are elongate with very stretched fibrillar cytoplasms resulting in a distinct dendritic-like appearance to many of the cells. A few of the cells have a more syncytial-like appearance with bi and multinucleation.

Slide 4: When one examines the cells under higher magnification the nuclei are quite vesicular with inconspicuous nucleoli. The cytoplasms are lightly eosinophilic in nature although in a few of the cells fine perinuclear vacuoles are identified which in some of the cells imparts a signet ring-like appearance. While there is some degree of atypia there is no overt pleomorphism to be concerned that one is dealing with a malignant lesion.

Slide 5: The tumor is extensively positive for S-100.

Slide 6: CD56 is strongly positive as well. The findings are those of a rare tumor falling under the designation of nerve sheath myxoma.