Seborrheic Keratosis: A common, benign skin growth that can appear on the back of the head, often due to aging and sun exposure. It typically presents as a waxy, brown, or black growth.

Mole (Nevus): A melanocytic nevus can appear as a growth on the back of the head, ranging in color from light brown to black. Most moles are benign but can be a concern for melanoma.
Cyst (Epidermoid or Pilar): Benign cysts that can form on the scalp, sometimes appearing as a growth. They can become inflamed or infected.
Wart (Verruca Vulgaris): Caused by the human papillomavirus (HPV), warts can appear anywhere on the body, including the back of the head, and are generally benign.

Melanoma: Although less common, melanoma is a deadly form of skin cancer that can appear as a new or changing growth on the back of the head. Early detection is crucial for treatment.
Basal Cell Carcinoma (BCC) or Squamous Cell Carcinoma (SCC): These are types of skin cancer that can appear on sun-exposed areas, including the back of the head. While generally less aggressive than melanoma, they can cause significant local damage if not treated.
Metastatic Lesion: In rare cases, a growth on the back of the head could be a metastasis from a cancer elsewhere in the body, such as breast, lung, or prostate cancer.

Dermatofibroma: A rare, benign growth that can appear after minor injury, typically on the legs but can occur elsewhere, including the back of the head.
Keratoacanthoma: A low-grade, or sometimes considered benign, malignancy of the skin that resembles a volcano, typically appearing on sun-exposed areas.
Pilomatrixoma: A rare, benign tumor arising from the hair follicle matrix, more common in children and young adults, which can appear as a firm, mobile nodule on the scalp.