Certified Hand Therapist (CHT) Practice Exam

What type of tumor results from a penetrating traumatic injury that drives epithelium into the subcutaneous tissue?

1. Inclusion cyst

2. Glomus tumor

3. Xanthoma

4. Schwannoma

The correct answer is: Inclusion cyst

An inclusion cyst is indeed the correct answer because it typically forms when skin is unintentionally punctured or penetrated, allowing epithelial cells to become trapped within the subcutaneous tissue. This trapped epithelium can proliferate, leading to the formation of a cyst filled with keratin or other materials. Inclusion cysts are often seen following trauma, where the keratin-producing epithelium is buried and can result in a localized area of swelling or lump under the skin. This can occur in various locations on the body, including the hands and other areas subject to trauma. The other options, while being types of tumors or cysts, do not result specifically from the process described in the question. Glomus tumors, for example, are a type of vascular tumor often associated with deep under the nail and are not a direct result of trauma driving epithelium into deeper tissues. Xanthomas are associated with lipid deposits and may not be related to trauma, and Schwannomas are nerve sheath tumors that arise from Schwann cells, not from skin epithelium penetrating into subcutaneous layers.