Malignant melanotic nerve sheath tumor in pleural effusion: Deceitful cytology with significant repercussions

Cytomorphology of metastatic malignant peripheral nerve sheath tumour present in pleural fluid: Case study and literature review

The cytomorphology of MPNST in effusion specimens is rarely described. In this paper, the detailed cytopathological and immunohistochemical characteristics of metastatic MPNST has been described in pleural effusion. Patients' medical history and the judicious utilization of ancillary studies contribute to ensure precise cytological diagnoses. The cytomorphology of malignant peripheral nerve sheath tumour (MPNST) in effusion specimens can be diagnostically challenging. The author presents detailed cytopathological and immunohistochemical characteristics of a case of metastatic MPNST in pleural effusion.

Malignant Melanotic Nerve Sheath Tumor

Malignant melanotic nerve sheath tumors are uncommon pigmented tumors of Schwann cell origin, most often found along the spinal nerves. Although well-described in the literature, the tumors are quite rare, making up <1% of nerve sheath tumors. Physicians are, therefore, often unfamiliar with both the appearance and the optimal treatment of such tumors. Morphologically, many imaging features overlap with schwannomas and neurofibromas. Nevertheless, the malignant melanotic nerve sheath tumors are crucial to identify. They can be extremely aggressive, and the management of these tumors is considerably different from their benign counterparts. In this radiology-pathology review, we will highlight the imaging appearance, histologic features, surgical resection, and subsequent therapeutic strategies in a patient with a lumbar malignant melanotic nerve sheath tumor.

Rare malignant melanotic nerve sheath tumors of the upper limb nerves: utility of high-frequency ultrasonography in preoperative imaging

Melanotic nerve sheath tumor (MNST) is a rare variant of schwannoma. Here, we report an unusual case of multiple MNST lesions located in the upper limb nerves. The patient presented with a mass on the left wrist in 2016 and another mass on the left thumb in 2017. In both instances, magnetic resonance imaging scans confirmed multiple giant-cell tumors of the tendon sheath. Persistent pain in the left upper limb and numbness in the ring finger and little finger recurred in 2021. High-frequency ultrasound (HFUS) showed that the left brachial plexus nerves (C5-8) were widened compared with those on the contralateral side; the neuroma formed at the lateral cord, and the median nerve was markedly thickened. The surgical findings were consistent with the ultrasound results. Pathology confirmed that the tumors were malignant MNSTs. HFUS is important for preoperative diagnosis and lesion localization, even identifying some lesions that are unrecognized on magnetic resonance imaging; thus, HFUS is crucial for improving surgical strategy and decision-making.