Squamous cell carcinoma of the oral cavity is among the most common malignant tumors, commonly observed in people between the fifth and seventh decades of life, and is considered rare in people under 30 years of age. A 16-year-old female patient undergoing leukemia treatment attended a specialized dental care service to assess a recurrent lesion on the lateral edge of the tongue, on the right side, complaining of burning and pain. Incisional biopsy of the lesion was performed, and the material was sent for immunohistochemical study, which showed squamous mucosa with a focus on high-grade dysplasia of the lining epithelium and infiltrating neoplasia, in addition to positive expression of the p63 protein, indicating that the lesion was an invasive squamous cell carcinoma. After diagnosis, the patient was referred for cancer treatment with a head and neck surgery team. Squamous cell carcinoma of the oral cavity is among the most common malignant tumors, commonly observed in people between the fifth and seventh decades of life, and is considered rare in people under 30 years of age. A 16-year-old female patient undergoing leukemia treatment attended a specialized dental care service to assess a recurrent lesion on the lateral edge of the tongue, on the right side, complaining of burning and pain. Incisional biopsy of the lesion was performed, and the material was sent for immunohistochemical study, which showed squamous mucosa with a focus on high-grade dysplasia of the lining epithelium and infiltrating neoplasia, in addition to positive expression of the p63 protein, indicating that the lesion was an invasive squamous cell carcinoma. After diagnosis, the patient was referred for cancer treatment with a head and neck surgery team.