A case report of primary lower rectal spindle cell melanoma: Challenging diagnosis, difficult treatment, and poor prognosis

Spindle cell melanoma (SCM) is a rare morphological subtype of mucosal melanoma, especially located in the lower rectal or anal region. The diagnosis of SCM is challenging because it may share some morphological and immunohistochemical features with desmoplastic melanoma or other malignant tumors. Anorectal melanoma is characterized by aggressive biological behavior, a high incidence of local recurrence and metastasis, and poor outcomes. We herein report a 56-year-old female patient with a challenging diagnosis of primary rectal SCM with a poor prognosis and review the literature.