A hard lump on the inner thigh could be caused by an infection, boil, tumor, trauma, soft tissue sarcoma or hidradenitis suppurtiva. Some of these causes are superficial and require little treatment, while others require medical intervention, according to Med-Health.
An infection or boil is typically caused by bacteria, yeast or skin trauma on the inner thigh. If hair follicles become inflamed from a bacterial infection, for example, the patient can develop folliculitis. A boil can be caused by excess moisture where the thighs rub together.
Hidradenitis suppurtiva is a common condition that causes bumps on the inner thigh. It results from a build-up of skin cells and oils that block the hair follicles. It can cause blackheads, red lesions or small, hard bumps, according to Mayo Clinic. Patients should visit a doctor if symptoms persist for more than a few weeks or if the bumps become painful.
A soft tissue sarcoma or tumor can also cause bumps on the inner thigh, according to Patrick Maguire, M.D. A tumor can be either cancerous or benign, but STS is a highly aggressive form of cancer that requires immediate intervention. It is diagnosed with a biopsy of the mass.
One of the most common causes of lumps in the thigh is trauma. Any injury can cause bumps underneath the skin, including blunt force trauma and strained muscles. These conditions usually resolve themselves, but patients should seek treatment if they are concerned.