Metachronous Occurrence of Granular Cell Tumor in Breast Skin and Scalp: Diagnostic Challenging Differentiating Benign from Malignant and a Literature Review.

Granular cell tumor (GCT) is a Schwann cell related benign neoplasm of soft tissue. GCT is an uncommon entity that occurs in a wide variety of body sites, but it is generally presented in the skin, oral cavity, superficial soft tissue, and respiratory and digestive tracts. Most of the GCTs are benign but clinically and radiologically these may mimic malignancy. Histopathological diagnosis is gold standard for establishing the true nature of the lesion. GCT is most commonly solitary but in about 10% of cases can be multifocal, usually involving various skin and soft tissue sites versus involving various internal sites. Therefore, these can involve skin and soft tissue or submucosa and viscera. GCT is usually benign; however, local recurrence is common due to incomplete removal. Malignant cases are rarely reported in 1-2% of cases. In this study, we report clinical and histopathological findings of a 36-year-old woman with metachronous GCT in breast and scalp. The clinical features raise the question of whether these are metachronous benign GCTs or whether this is establishment of malignant behavior. The aim of this report is to present the histopathological and clinical features of GCT and the diagnostic challenge of differentiating benign from malignant GCT.