Trichoblastoma is closely related to trichoepithelioma, another benign follicular tumor that arises from follicular germ cells. Some experts consider trichoepithelioma to be a superficial variant of trichoblastoma; trichoepithelioma arises in the superficial dermis, and trichoblastoma arises in the deep dermis and subcutis.
Trichoblastoma is one of the most common tumors to arise within a nevus sebaceus, a congenital hamartoma most often found on the scalp. Trichoblastomas have been reported to occur in Curry-Jones syndrome (patchy hypopigmentation, polysyndactyly, cranial defects, and ophthalmic and gastrointestinal abnormalities).
Malignant transformation of trichoblastoma into a trichoblastic carcinoma, trichoblastic sarcoma, or trichoblastic carcinosarcoma is exceedingly rare. Malignant transformation most commonly presents as a long-standing lesion that suddenly enlarges. There is limited available data concerning the behavior and prognosis of malignant trichoblastic neoplasms; however, distant spread and death have been reported, and this aggressive behavior may be more common in sporadic cases.
D23.9 – Other benign neoplasm of skin, unspecified
277942005 – Trichoblastoma
- BCC – Trichoblastoma may mimic BCC clinically and histopathologically. Trichoblastoma does not typically have cellular atypia, apoptotic bodies, or mitoses, which can help distinguish it from BCC. Immunohistochemistry can also help distinguish trichoblastoma from BCC.
- Merkel cell carcinoma – Presents as a rapidly expanding pink to bluish red, firm nodule.
- Spiradenoma – Associated with pain and tenderness to palpation.
- Cutaneous lymphadenoma
- Pilar cyst – Smooth and mobile on palpation.
- Epidermoid cyst – Freely movable on palpation and may have a central punctum.
- Keloid – Occurs at a site of previous trauma and is more common in darker skin.
- Cutaneous neuroma
- Seborrheic keratosis – Look for stuck-on appearance clinically and for horn cysts on dermoscopy.
- Sebaceous adenoma – Associated with Muir-Torre syndrome.
- Trichilemmal carcinoma
- Pilomatrix carcinoma