Abstract

Introduction: Trichoblastoma is an uncommon benign neoplasm largely composed of follicular germinative cells. Pigmented trichoblastoma or a melanotrichoblastoma is a rare variant with only few reported cases in the literature.

Case Summary: A 58 year old Filipino male consulted for a 2 year history of a black papule on the left shoulder gradually enlarging to a bluish-black tumor with no associated symptoms of pain or pruritus. On physical examination, there is a solitary well demarcated irregularly shaped black smooth surfaced tumor on the left shoulder measuring 1.2 x 1.3 x 0.5 cm. Dermoscopy revealed bluish-black globules and yellowish-white central structureless areas. A 4mm punch biopsy was done showing lobules of basaloid cells with peripheral palisading and melanin pigment within the lobules, associated with a fibromyxoid stroma. Trichoblastoma was the initial histopathologic diagnosis. Since melanin deposition is an uncommon feature of trichoblastoma, a pigmented basal cell carcinoma was also a consideration. To completely rule out a basal cell carcinoma, wide excision with 5 mm margins was done with full thickness graft from the inguinal area. With a larger area of histologic tissue demonstrating no connection to the epidermis, absence of retraction artifact and the presence of fibromyxoid stroma, basal cell carcinoma was ruled out and a final histopathologic diagnosis of a pigmented trichoblastoma was given. Post-operatively, the graft had a good uptake and there was no recurrence of the lesion.

Conclusion: This case describes the clinico-pathologic and dermoscopic features of a rare variant of an already rare tumor: a pigmented trichoblastoma.

Citation

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Keywords

pigmented trichoblastoma, melanotrichoblastoma, trichoblastoma