Melanotic schwannoma of thoracic spinal root mimics metastatic melanoma: a potential pitfall for misdiagnosis

Abstract

Melanotic Schwannoma (MS) is a kind of rare subtypes of Schwannoma. In this tumor, amounts of melanin always mislead inexperienced pathologists to a diagnosis of primary or metastastic melanoma. Different from the ordinary Schwannoma, MS is considered as a low malignant nerve sheave tumor. Here we present a case of MS arising from the thoracic spinal and initially was misdiagnosed as metastastic melanoma. But the patient followed a benign course, without recurrent in 30 months follow-up.

Keywords: Melanotic tumor; Schwannoma; diagnosis; differentiation; melanoma.

Figure 1

CT scanning for thoracic spinal. (A) dumb-bell shape mass across the intervertebral foramina, T7 vertebral body showed destructive change. (A) A well circumscribed dumb-bell shape mass, and the density is similar to the soft tissue (B).

Figure 2

Dense melanin pigments showed in the mass. (A) The tumor consisted of ovoid cells with mild atypical after depigmenting. Rare mitosis was seen. (B) Tumor cells were reactive to HMB-45 (C) and sporadic reactive for S-100. (D) MIB-1 revealed less than 1% cells were positive. (E) (A) H & E, 40×, (B) H & E, 400×, (C, E) IHC, 200×, (D) IHC, 100×.