Atypical giant trichoblastoma: An unusual presentation

Don't Judge a Tumor by Its Biopsy!

Trichoblastomas (TBs) are extremely rare, benign hair germ tumors that can mimic basal cell carcinoma (BCC). They usually arise on the head or neck and have a potential for malignant transformation, albeit it is rare. We report a case of giant TB on the forehead of a 75-year-old otherwise healthy woman. Since the age of 20 she reported a bulge on her forehead, in which a superficial-looking wound had now developed. Initially a dermatologist biopsied the tumor suspecting a BCC, which the histological analyses confirmed. The patient was then referred to the Department of Plastic Surgery for complete excision of the carcinoma, including the large frontal bulge. Surprisingly, the concluding pathology report changed the diagnosis from a BCC to a TB. Current management of most skin lesions relies on the histopathological subtype of a single punch biopsy. Many benign and malignant dermatological entities may mimic BCC, and therefore misdiagnosis can lead to either unnecessary excision or delayed treatment of metastatic disease. Mimics may include various types of nonneoplastic processes, benign adnexal tumors, including TB, or cutaneous carcinomas with basaloid features. A single punch biopsy is not always adequate in making the correct diagnosis. Although it is considered the gold standard, the clinical assessment is just as important. Due to its potential for malignant transformation, it is recommended to excise TB with negative margins.

Trichoblastomas Mimicking Basal Cell Carcinoma: The Importance of Identification and Differentiation

Trichoblastoma is a rare, slow-growing, benign cutaneous tumor derived from follicular germinative cells. Trichoblastoma commonly appears as an asymptomatic, symmetrical, well-circumscribed, skin-colored to brown or blue-black papule or nodule. It may appear clinically and histologically similar to basal cell carcinoma, making its diagnosis challenging. Even on dermoscopy, it is challenging to differentiate trichoblastoma from basal cell carcinoma. In practice, it is important to differentiate the two, because the choice of treatment and resulting prognosis differ between the lesions. Surgical biopsy to analyze histopathological and immunohistochemical differences is the gold standard for diagnosing and differentiating trichoblastoma from basal cell carcinoma. Trichoblastoma typically has a favorable prognosis, with a low incidence of recurrence, progression or association with malignancy. This paper provides a review of the epidemiology, clinical presentation, dermoscopy, histology, immunochemistry, treatment, and prognosis of trichoblastoma.