Extensive glandular and neuroendocrine differentiation of a malignant peripheral nerve sheath tumor in a neurofibromatosis-1 patient

Abstract

The histologic diagnosis of a malignant peripheral nerve sheath tumor (MPNST) is complex with no defining biomarkers or generally accepted diagnostic criteria, but based on whether it is identified arising from a peripheral nerve, arising from a benign nerve sheath tumor, in the setting of neurofibroma or when its constellation of features suggest a Schwann-cell differentiation [1- 3]. Further complicating the histologic diagnosis is the small subset of these tumors with divergent differentiation demonstrating various heterologous elements [4]. Divergent differentiation presenting in a glandular form in MPNST is particularly rare, though has been described, usually in context of Neurofibromatosis I (NF1) patients, as discrete localized areas occasionally associated with neuroendocrine features [3,5,6]. Being aware of the possible extent of variable histologic features is critical for diagnosis, particularly if only a needle core biopsy is provided. We present a case of MPNST arising in a 20-year-old woman with NF1 found to have an unusual extensive glandular and neuroendocrine divergent differentiation comprising more the 75% of the tumor, arising from a plexiform neurofibroma. The patient had a prior MPNST resected without evidence of divergent differentiation, and then a subsequent metastasis to the base of the skull with similar glandular histology following our presenting case. To our knowledge, such extensive glandular and neuroendocrine differentiation has not been previously described in these tumors.