The common causes of hard lumps growing inside testicles are testicular inflammation, testicular cysts, testicular tuberculosis and varicocele. 1. Orchitis: usually caused by staphylococcus and E. coli bacteria. Testicular inflammation often has testicular swelling, pressure and pain, and when palpating, there is a hard lump in the testicle, if pus fluctuates on palpation, the patient’s whole body also has the symptoms of high fever and chills. 2. Testicular cysts: testicular cysts often have no obvious clinical manifestations, and some patients may have a slight feeling of swelling. Testicular cysts vary in size, and as they continue to grow, they will gradually develop pressure pain and occupying lesions. On palpation, a hard lump is found in the testicle, which is painless. Ultrasonography can find single or multiple round or oval liquid areas with clear boundaries. 3. Testicular tuberculosis: Testicular tuberculosis is mostly caused by prostate, vas deferens, seminal vesicles, epididymal tuberculosis spreading from each other, which is mainly manifested as vague pain in testicles with a feeling of falling, enlarged with a hard lump, slightly hard in texture, and the prognosis is poor if not treated in time. 4. Varicocele: Varicocele is mainly manifested as testicles or scrotum have a feeling of swelling, scrotum is enlarged, the appearance of scrotum can be seen in the tortuous expansion of the veins, testicular hardness and so on. There may be other reasons for the appearance of testicular hardness, the patient needs to consult the doctor in time for examination and early treatment.