What is the origin of the cells in a pigmented nodule with ulceration lateral to the nose in a 55-year-old male patient with no detected lymph nodes?

Origin of Cells in a Pigmented Nodule Lateral to the Nose

The pigmented nodule with lateral ulceration lateral to the nose in this 55-year-old male patient most likely originates from melanocytes (option B). This conclusion is based on the clinical presentation of pigmentation and ulceration, which are characteristic features of melanocytic lesions, particularly melanoma 1.

Clinical Features Supporting Melanocytic Origin

• Pigmentation: The presence of pigmentation in the nodule indicates melanin production, which is a characteristic feature of melanocytic cells 1
• Ulceration: Lateral ulceration is a common feature in melanomas and represents a negative prognostic factor 1
• Location: The face, including the area lateral to the nose, is a common site for melanoma development due to sun exposure, which is a major risk factor for melanocytic transformation 1
• Age and occupation: The patient's age (55 years) and occupation (worker - suggesting possible sun exposure) align with risk factors for melanocytic lesions, particularly melanoma 2

Diagnostic Considerations

The clinical presentation aligns with the revised checklist for suspected malignant melanoma 2:

Major signs (present in this case):

• Change in color (pigmentation)
• Diameter ≥ 7 mm (implied by the description as a nodule)

Minor signs (present in this case):

• Crusting or bleeding (ulceration)

Histopathological Confirmation

Histopathological examination would be necessary to confirm the diagnosis, with immunohistochemistry markers specific for melanocytes:

• MART-1/HMB45: These melanocyte-specific markers would be positive in melanocytic lesions 2
• S-100: A marker typically positive in melanocytic lesions 3

Differential Diagnosis

While the clinical presentation strongly suggests a melanocytic origin, other possibilities include:

1. Basal cell carcinoma (BCC): Can present as a pigmented nodule but typically has pearly borders and telangiectasia
2. Basosquamous carcinoma: Can present with pigmentation and ulceration but is derived from keratinocytes 4
3. Seborrheic keratosis: Usually has a "stuck-on" appearance without ulceration

Clinical Approach

For definitive diagnosis, a complete excisional biopsy with a 2 mm margin of normal skin is recommended 2. The histopathological examination should include:

• Confirmation of melanocytic nature through immunohistochemistry
• Assessment of Breslow thickness
• Evaluation of ulceration extent
• Clark level of invasion
• Presence of regression

Conclusion

Based on the clinical presentation of a pigmented nodule with lateral ulceration in a sun-exposed area of the face in a 55-year-old male, the most likely cell of origin is melanocytes (option B). The other options (keratinizing cell, non-keratinizing cell, or pluripotent cell) are less likely given the clinical features described.