Malignant Peripheral Nerve Sheath Tumor of the Thigh Invading the Superficial Femoral Artery, with Necrotic Lung Metastases as Presenting Symptoms

A NF1 (neurofibromatosis 1) patient developed multiple necrotic lung metastases from a sciatic malignant peripheral nerve sheath tumor (MPNST) invading the superficial femoral artery. The first diagnosis was metastases of a non-small-cell adenocarcinoma because the right calf MPNST was not clinically noticeable ant that the chest/abdomen PET/CT did not include the region of the legs. When the MPNST was diagnosed, new histological analysis on the metastases changed the diagnosis to that of epithelioid undifferentiated sarcoma. The article deals with the sometimes-delayed diagnosis in those NF1 patients with large palpable masses and chronic pain pre-existing the malignant transformation, and discusses the difficulty of the biopsy of necrotic metastases.