Cytologic findings in pigmented melanotic schwannoma: a case report.

Background: Psammomatous melanotic schwannoma (PMS) is a rare pigmented neural tumor most commonly occurring in the paraspinal region. This rare tumor can cause diagnostic difficulties in imprint cytology due to cellular details masked by heavy melanin pigments.

Case: A 37-year-old man presented with an 8-month history of lower back pain with no stigmata of Carney's syndrome on physical examination. Radiologic studies showed a 3.5-cm epidural mass in the region of the left L2 nerve root. Imprint smears from the biopsied tissue fragment revealed mainly epithelioid cells with prominent nucleoli and variable amounts of cytoplasmic brown pigment, indicating a pigmented tumor with neuronal origin PMS, which was confirmed by histologic and immunohistochemical studies of the resected tumor.

Conclusion: PMS is a rare entity, and it is important to differentiate PMS from other pigmented tumors in the spinal canal, such as melanocytoma and malignant melanoma. It should be included in the differential diagnosis to avoid overtreatment.