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The observation that vitamin A (retinol) has antikeratinizing properties has led to the development of synthetic retinol derivatives (retinoids) for the treatment of a variety of skin disorders characterized by abnormal keratinization. The goal of research in this area is the synthesis of retinoids that would have a more favorable therapeutic: toxic ratio than retinol itself. A limiting factor in the use of any vitamin A analogue is that, even with a more favorable therapeutic: toxic ratio, large pharmacologic doses are required that produce side effects related to the drug's action in most individuals. With few exceptions, all of the side effects are those seen from mega-vitamin A ingestion, primarily affecting the mucocutaneous, skeletal, and central nervous systems. Most of the side effects from excess vitamin A are reversible, with notable exceptions being those involving hepatic and osseous tissues. In terms of reversibility from synthetic retinoids, the experience to date has been incomplete, so there remains imprecise information as to the incidence and the persistence of toxic effects after drug withdrawal.

: The authors report an unusual case of malignant peripheral nerve sheath tumor with malignant differentiation arising as a subcutaneous nodule in the thigh of a 53-year-old woman with a history significant for neurofibromatosis type 1. Peripheral nerve sheath tumors containing a glandular component, commonly referred to as glandular peripheral nerve sheath tumors, are rare neoplasms found largely in patients with neurofibromatosis type 1. These tumors are frequently malignant; recognition of metastatic potential is made based on the atypical spindle-cell component. Rarely, as in our case, the glandular component is also histologically malignant. Only 5 such tumors have been described in the literature to date. Glandular differentiation, particularly with malignant features, can be a potentially misleading feature when found as a component of malignant peripheral nerve sheath tumors and raise a wide spectrum of differential diagnoses, including metastatic Sertoli-Leydig tumors. The patient is free of disease for 22 months after wide tumor reexcision, which contrasts with previously reported devastatingly poor prognosis of these tumors.

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