Differential Diagnosis for the Patient's Condition
The patient presents with an ulcerative but painless oral lesion on his lower lip, which has been present for approximately two weeks. Given the patient's history and physical examination findings, the following differential diagnoses are considered:
Single Most Likely Diagnosis
- Squamous cell carcinoma: This is the most likely diagnosis given the patient's 30-pack-year history of cigarette smoking and the presence of a nontender, ulcerative lesion with raised edges on the lower lip. The lesion's location and the patient's smoking history are significant risk factors for squamous cell carcinoma.
Other Likely Diagnoses
- Syphilis: Although the patient's rapid plasma reagin (RPR) and fluorescent treponemal antibody absorption (FTA-ABS) tests are negative, syphilis cannot be completely ruled out, especially given the patient's partner was recently treated for syphilis. However, the negative serology results and the lack of other symptoms make this less likely.
- Traumatic ulcer: Despite the patient's denial of trauma, a traumatic ulcer is possible, especially if the patient is unaware of or forgot a traumatic event. However, the absence of a clear history of trauma and the lesion's appearance make this less likely.
Do Not Miss Diagnoses
- Infectious diseases (e.g., tuberculosis, leprosy, or other bacterial or fungal infections): These conditions can present with oral lesions and are important to consider, especially in immunocompromised patients or those with exposure to infectious diseases. Although less likely, missing these diagnoses could have significant consequences.
- Lymphoma: Although rare, lymphoma can present with oral lesions and cervical lymphadenopathy, making it a "do not miss" diagnosis.
Rare Diagnoses
- Other types of oral cancer (e.g., basal cell carcinoma, melanoma): These are less common than squamous cell carcinoma but should be considered in the differential diagnosis.
- Autoimmune disorders (e.g., pemphigus, lupus): These conditions can present with oral lesions, although they are less likely given the patient's presentation and lack of other symptoms.
- Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis): This rare autoimmune disorder can present with oral lesions, although it is unlikely given the patient's lack of other symptoms (e.g., respiratory or renal involvement).