**Core Concept**
Squamous cell carcinoma (SCC) is a type of malignant neoplasm that arises from the epithelial cells of the skin or mucous membranes. It is characterized by its aggressive behavior and potential to metastasize to regional lymph nodes.

**Why the Correct Answer is Right**
The patient's presentation of an ulcerated lesion on the tongue and a mass in the submandibular gland triangle is highly suggestive of SCC. SCC of the tongue is a type of oral cavity cancer that often presents with pain, bleeding, or difficulty swallowing. The presence of a mass in the submandibular gland triangle indicates regional lymphadenopathy, which is a common site for metastasis in SCC. The histopathological hallmark of SCC is the presence of atypical squamous cells with keratinization and invasion of the basement membrane.

**Why Each Wrong Option is Incorrect**

**Option A:** Lymphoma is a type of malignant neoplasm that arises from the lymphoid cells of the immune system. While lymphoma can present with lymphadenopathy, it is less likely to cause a palpable mass in the submandibular gland triangle and is typically associated with systemic symptoms such as fever and weight loss.

**Option C:** Metastatic skin cancer is unlikely in this case, as the patient's primary complaint is an ulcerated lesion on the tongue, and there is no mention of a primary skin cancer.

**Option D:** Benign mixed tumor, also known as pleomorphic adenoma, is a type of salivary gland tumor that is typically benign and slow-growing. It is unlikely to cause a palpable mass in the submandibular gland triangle and is not associated with regional lymphadenopathy.

**Clinical Pearl / High-Yield Fact**
The patient's presentation of an ulcerated lesion on the tongue and a mass in the submandibular gland triangle is highly suggestive of SCC. It is essential to consider SCC in the differential diagnosis of oral cavity cancers, especially when there is evidence of regional lymphadenopathy.

**✓ Correct Answer: B. Squamous cell carcinoma**