Pigmented trichoblastoma arising from the nevus sebaceous: a rare case in Korea

Trichoblastoma Arising From the Nevus Sebaceus of Jadassohn

Trichoblastoma is a rare benign skin adnexal tumour, belonging to the category of trichogenic tumours. The clinical and histological findings may often be confused with basal cell carcinoma, a malignant epidermal skin tumour. We report here a case of a 70-year-old man presented with a dome-shaped, dark-pigmented nodule within a yellowish hairless plaque on the scalp. The plaque had existed since childhood. However, the central pigmented nodule began appearing three months ago and enlarging gradually. The patient had no medical history. Furthermore the physical examination revealed a translucent, verrucous, and yellowish plaque, with central and pigmented nodule measuring 0.7 × 0.5 cm. Also basal cell carcinoma and trichoblastoma's diagnosis were discussed. The patient was subsequently referred to the plastic surgery department, where he underwent a total excision. The histological examination was in favour of trichoblastoma arising from the nevus sebaceus. After 24 months of checking, no recurrence was observed. Trichoblastoma is a benign adnexal tumour. Its progression to malignant trichoblastoma (or trichoblastic carcinoma) is possible, but remains exceptional. Therefore, complete excision should be proposed to the patient at the time of diagnosis.

Pigmented Trichoblastoma of Nose: An Unusual Occurrence

Nevus sebaceus of Jadassohn is a congenital tumour affecting the scalp and face. It is usually presented as a pigmented patch or plaque. It is a complex cutaneous hamartoma which involves pilosebaceous follicle, epidermis and adnexal structures. Tumours that arise from nevus sebaceous are basal cell carcinoma, syringocystadenoma papilliferum, trichoblastoma and hidradenoma. The progression and frequency of the tumour increase with the age. Here we present a case of pigmented trichoblastoma over the external nose. It was a case of an elderly woman presenting with a painless swelling over the external nose which was soft, non-tender and with well defined margins.

A collision tumour consisting of malignant trichoblastoma and melanosarcoma in a rabbit

A 7-year-old mixed breed neutered female rabbit (Orytolagus cuniculus) developed a solitary black nodular mass (1 cm in diameter) in the skin of the right flank. Microscopically, the mass consisted of an admixture of neoplastic trichoblasts and melanocytes. The former were arranged as solid, trabecular, island-like and gland-like structures and the cells had oval nuclei with prominent nucleoli and lightly eosinophilic scant cytoplasm. The latter population exhibited prominent nuclear atypia and high mitotic index in the clusters of a few cells or single cells. Immunohistochemically, the neoplastic trichoblasts expressed cytokeratins and E-cadherin, while the neoplastic melanocytes expressed vimentin, S100 protein, melan-A and melanoma antigen. A diagnosis of collision tumour involving malignant trichoblastoma and melanosarcoma was made.