**Core Concept**
Kaposi's sarcoma is a type of cancer that affects the skin and mucous membranes, characterized by the proliferation of abnormal cells in the lymphatic vessels. It is a well-documented complication of immunosuppression, particularly in individuals with HIV/AIDS.

**Why the Correct Answer is Right**
Kaposi's sarcoma is strongly associated with human herpesvirus 8 (HHV-8) infection, which is a member of the herpesvirus family. The virus is thought to play a key role in the development of the disease, particularly in individuals with compromised immune systems. In HIV-positive homosexual males, Kaposi's sarcoma is a common neoplasm due to their increased susceptibility to opportunistic infections and malignancies. The disease typically presents as skin lesions, which can be disfiguring and potentially life-threatening if left untreated.

**Why Each Wrong Option is Incorrect**
**Option A:** Non-Hodgkin's lymphoma is a type of cancer that affects the immune system, but it is not as strongly associated with HIV infection as Kaposi's sarcoma. While it is a common malignancy in HIV-positive individuals, it is not the most common neoplasm in this population.

**Option B:** Glomus tumor is a rare, benign tumor that arises from the glomus body, a small structure involved in temperature regulation. It is not associated with HIV infection or immunosuppression, and it is not a common neoplasm in HIV-positive homosexual males.

**Option D:** This option is incorrect because Kaposi's sarcoma is indeed a common neoplasm among HIV-positive homosexual males.

**Clinical Pearl / High-Yield Fact**
Kaposi's sarcoma is often referred to as an "AIDS-defining illness," meaning that its presence is a diagnostic criterion for HIV/AIDS. This is because the disease is a hallmark of immunosuppression and is rarely seen in individuals with intact immune systems.

**✓ Correct Answer: C. Kaposi's sarcoma**