Is it normal for a benign nevus (mole) to regress over time, leaving behind pigmented globuli and a vascular network with depigmentation?

Regression of Benign Nevi: Clinical Significance and Pattern Recognition

While benign nevi can undergo spontaneous regression and depigmentation over time, the specific dermoscopic pattern you describe—residual pigmented globuli with vascular network and surrounding depigmentation—requires excisional biopsy to definitively exclude melanoma, as regression is also a concerning feature in melanoma and partial examination risks misdiagnosis.

Understanding Nevus Regression

Normal Evolutionary Changes in Benign Nevi

Benign congenital and acquired melanocytic nevi commonly undergo predictable changes over time, including:

• Spontaneous lightening and depigmentation can occur as a normal phenomenon in benign nevi 1
• Changes in pigmentation pattern including becoming more mottled, speckled, or showing homogeneous or heterogeneous lightening are recognized benign changes 2
• Textural changes such as becoming more raised, verrucous, or papillated represent normal evolution 2

The Critical Distinction: Regression as a Warning Sign

However, the presence of regression carries significant diagnostic weight:

• Regression is a mandatory histopathological parameter that must be documented when evaluating melanocytic lesions, as it appears in both the NIH consensus conference and French Consensus Conference criteria for melanoma assessment 3
• The fact that "presence and extent of regression" is specifically required in melanoma pathology reports indicates its clinical significance as a potential marker of malignancy 3

Dermoscopic Features: Interpreting Your Specific Pattern

Concerning Elements in Your Description

The pattern you describe—three pigmented globuli with vascular network and surrounding depigmentation—contains elements that warrant careful evaluation:

• Residual pigmented globuli in a regressing lesion could represent either benign nevus remnants or residual melanoma
• Vascular network development in a previously pigmented lesion represents a structural change that requires histological correlation
• Depigmentation surrounding the lesion could represent benign regression but is indistinguishable from melanoma regression without histology

Why Partial Assessment Is Inadequate

Complete excisional biopsy is essential rather than clinical observation alone because:

• Risk of misdiagnosis exists if a melanocytic lesion is only partially examined through dermoscopy or clinical assessment 3
• Examination of the entire lesion is necessary to assess all histological parameters, particularly when regression is present 3
• Melanoma can present as deep dermal or subcutaneous nodules without surface color change, making palpation and complete histological examination critical 2

Clinical Management Algorithm

Immediate Action Required

1. Perform excisional biopsy with scalpel (not laser or electro-coagulation, as tissue destruction compromises diagnosis) 3
2. Document excision margins in the operation note 3
3. Send entire specimen to pathologist experienced in melanocytic lesions 3, 1, 2

Rationale for Excision Over Observation

• If the lesion is benign, no further treatment is needed after excision 3
• If malignant, complete assessment of Breslow thickness, margins, and extent of regression is only possible with full excision 3
• Dermoscopic monitoring alone, while useful for stable lesions, showed that melanomas can develop subtle changes over 8-54 months requiring multiple visits to detect 4

Critical Pitfalls to Avoid

Do Not Rely on Dermoscopy Alone for Regressing Lesions

• While dermoscopic monitoring is valuable for stable atypical nevi, it is designed to detect changes over time, not to definitively characterize already-changing lesions 4
• The melanoma-to-benign ratio in monitored lesions requiring excision was 1:3.4, meaning even with careful monitoring, distinguishing benign from malignant changes requires histology 4

Do Not Use Ablative Procedures

• Avoid pigment-specific lasers, curettage, or dermabrasion as these obscure future melanoma evaluation and cause pigment recurrence 2
• These techniques prevent assessment of critical parameters like Breslow thickness and extent of regression 3

Special Considerations

If This Is a Congenital Nevus

• Congenital melanocytic nevi carry a lifetime melanoma risk of 0.7-1.7% 1
• Melanoma in congenital nevi can present as deep nodules without overlying color change, emphasizing the need for palpation and complete excision when changes occur 2

Expected Histopathology Report

The pathologist should provide 3:

• Confirmation of melanocytic nature and benign vs. malignant diagnosis
• Presence and extent of regression (specifically documented)
• Breslow thickness if melanoma
• Margin assessment
• Presence of ulceration

In summary: While benign nevi can regress, the specific pattern you describe with residual pigmentation, vascular changes, and depigmentation cannot be reliably distinguished from regressing melanoma without complete excisional biopsy and histopathological examination.