Melanotrichoblastoma: A Histopathological Case Report of a Rare Pigmented Variant of Trichoblastoma

Background and clinical significance: Trichoblastomas are rare, mixed epithelial tumors with a mesenchymal component and hair follicle differentiation. Case presentation: Herein, we present a case report of a 51-year-old female patient presenting to the obstetrics and gynecology department with complaints of edema and erythema of the right Bartholin gland, and a lesion measuring 2 cm on the right lateral edge of the mons pubis, towards the inguinal fold. Marsupialization of the Bartholin gland was performed, as well as an incision into the pubo-inguinal lesion, which the patient depicted as grossly resembling an ingrown hair. Upon incision into the pubic–inguinal lesion, it was dark brown in color and spontaneously popped out of the subcutis, without an attempt at enucleation. Histology and subsequent immunohistochemistry of the lesion showed a blue basaloid tumor with an extensive pigment component located deep in the dermis that was sharply demarcated from the surrounding tissues. Conclusion: Immunohistochemistry was diffusely and strongly positive for epithelial markers; melanocytic markers were positive only in dendritic melanocytes dispersed within the tumors, and the proliferative index was low. As such, the tumor was identified as melanotrichoblastoma.