Nevus sebaceus may harbor other tumors, mostly benign adnexal tumors including trichoblastoma,
trichilemmoma, and syringocystadenoma papilliferum.
A
trichilemmoma is an uncommon, benign adnexal neoplasm derived from the outer root sheath of the hair follicle that presents as a solitary, skin-colored lesion on the midface.
Dermoscopic features include whitish, red and purple areas unlike those of hemangiomas with linear and hairpin like vessels at the periphery.6 Differential diagnosis includes hemangioma, glomus tumor, cutaneous lymphoma, dermatofibrosarcoma protuberans, leiomyoma, follicular cyst,
trichilemmoma and metastatic renal cell carcinoma, squamous cell carcinoma or signet-ring adenocarcinoma.1,7 Clinical differentiation is difficult; but characteristic histological features of nodular hidradenoma help in differentiating it from the above conditions.
In the third stage of their natural course, benign and malignant epithelial neoplasms can develop, including trichoblastoma, syringocystadenoma papilliferum, sebaceous epithelioma, basal cell carcinoma, and
trichilemmoma. (9)
The benign tumors are: Trichofolliculoma, Pilar sheath acanthoma, Fibrofolliculoma, Trichodiscoma, Trichoepithelioma, Trichoblastoma, Trichoadenoma, Pilomartricoma,
Trichilemmoma, Trichilemmal horn and Proliferating trichilemmal cyst.
Baptista, "Desmoplastic
trichilemmoma," The American Journal of Dermatopathology, vol.
Histologic features of a
trichilemmoma include lobular epidermal growth extending into the dermis, with glycogen-containing clear or pale-staining cells evident within the area of lobular growth and peripheral palisading of basophilic cells.
Trichoepithelioma should clinically be differentiated from basal cell carcinoma,
trichilemmoma, trichofolliculoma, syringoma and colloid milium.
Diagnostic value of CD34 immunostaining in desmoplastic
trichilemmoma. J Cutan Pathol.
Consider the diagnosis if you spot more than one
trichilemmoma.
They include benign adnexal tumors such as trichoblastoma syringocystadenoma papilliferum
trichilemmoma sebaceoma nodular hidradenoma hidrocystoma and eccrine poroma.
Histologic features of a
trichilemmoma include lobular epidermal growth extending into the dermis, with glycogen containing clear or pale-staining cells evident within the area of lobular growth and peripheral palisading of basophilic cells.