Diagnostic Change From Atypical Intraepidermal Melanocytic Proliferation to Melanoma is More Likely When Clinically Visible Residual Pigment Remains After Biopsy

Confocal microscopy, dermoscopy, and histopathology features of atypical intraepidermal melanocytic proliferations associated with evolution to melanoma in situ

BACKGROUND

Atypical intraepidermal melanocytic proliferations (AIMP) is a descriptive term sometimes applied to biopsies that do not fulfill diagnostic criteria of melanoma. They are common on sun-damaged skin, but their definition and management are controversial.

OBJECTIVE

To describe dermoscopic (DS), reflectance confocal microscopic (RCM) and histopathological features of AIMP and identify features associated with subsequent melanoma in situ (MIS).

METHODS

A retrospective analysis of AIMP lesions correlated with patient outcome at two melanoma tertiary centers between 2005 and 2015.

RESULTS

Thirty-four patients were included. Nine (26%) patients had MIS in subsequent biopsies. Predictors of later MIS were target-like pattern (OR:12.0 [CI: 1.23, 117.41]; P = 0.032) and high-density vascular network (OR:12 [CI: 1.23-117.41], P: 0.032) on DS, and presence of dendritic cells touching each other (OR:9.1 [CI: 1.54, 54.59], P = 0.014) on RCM. Clinical predictors of worse outcome included a previous history of MIS at the same site. Radiotherapy for AIMP had a high failure rate (all patients presented with recurrent disease, three as AIMP and two as MIS).

CONCLUSIONS

Considering that most cases in this series received non-surgical treatment at baseline, we recommend close monitoring for lesions with target-like pattern and density vascular network on DS and treatment for lesions with progression of atypia and/or with "confluent" dendritic cells on RCM. Although the number of patients in this series is very low, early surgery is recommended for MIS cases that recur as AIMP.

Defining the Histopathological Term Atypical Intraepidermal Melanocytic Proliferation: A Retrospective Cross-Sectional Study

BACKGROUND

Atypical intraepidermal melanocytic proliferation (AIMP) is a general term assigned to melanocytic proliferations of uncertain biological potential when a definitive histopathological diagnosis cannot be achieved. There are few data available describing the possibility of malignancy of AIMP, or ways to further define diagnosis.

OBJECTIVE

To determine the rate of diagnostic change of AIMP to melanoma or melanoma in situ (MIS) after conventional excision. In addition, to determine the role of immunohistochemistry (IHC) in defining AIMP biopsies.

METHODS

Retrospective cross-sectional, single-center review of biopsies with a diagnosis of AIMP with a follow-up conventional excision from 2012-2016 was performed. In a separate analysis, a search was performed for AIMP biopsied lesions in which IHC was subsequently performed.

RESULTS

The rate of diagnostic change of AIMP to MIS was 4.8% (8/167) after excision. Punch biopsy was a risk factor for diagnostic change to MIS (odds ratio 12.94, confidence interval 2.56-65.38, P = 0.008). The rate of diagnostic change of AIMP biopsies after examining with IHC was 21.3% (34/160) to MIS and 4.4% (7/160) to melanoma.

CONCLUSION

The possibility of malignancy of AIMP lesions must be taken into consideration when counseling patients and when planning treatment options. IHC is a useful tool and should be used in the evaluation of AIMP specimens.

Melanoma and melanoma in-situ diagnosis after excision of atypical intraepidermal melanocytic proliferation: A retrospective cross-sectional analysis

BACKGROUND

There is little evidence to guide surgical management of biopsies yielding the histologic descriptor atypical intraepidermal melanocytic proliferation (AIMP).

OBJECTIVE

Determine frequency of and factors associated with melanoma and melanoma in-situ (MIS) diagnoses after excision of AIMP and evaluate margins used to completely excise AIMP.

METHODS

Retrospective, cross-sectional study of 1127 biopsies reported as AIMP and subsequently excised within one academic institution.

RESULTS

Melanoma (in situ, stage 1A) was diagnosed after excision in 8.2% (92/1127) of AIMP samples. Characteristics associated with melanoma/MIS diagnosis included age 60-79 years (odds ratio [OR] 8.1, 95% confidence interval [CI] 2.5-26.2), age ≥80 years (OR 7.2, 95% CI 1.7-31.5), head/neck location (OR 4.9, 95% CI 3.1-7.7), clinical lesion partially biopsied (OR 11.0, 95% CI 6.7-18.1), and lesion extending to deep biopsy margin (OR 15.1, 95% CI 1.7-136.0). Average ± standard deviation surgical margin used to excise AIMP lesions was 4.5 ± 1.8 mm.

LIMITATIONS

Single-site, retrospective, observational study; interobserver variability across dermatopathologists.

CONCLUSION

Dermatologists and pathologists can endeavor to avoid ambiguous melanocytic designations whenever possible through excisional biopsy technique, interdisciplinary communication, and ancillary studies. In the event of AIMP biopsy, physicians should consider the term a histologic description rather than a diagnosis, and, during surgical planning, use clinicopathologic correlation while bearing in mind factors that might predict true melanoma/MIS.

Mohs micrographic surgery with melanoma antigen recognized by T cells 1 (MART-1) immunostaining for atypical intraepidermal melanocytic proliferation

BACKGROUND

The efficacy of Mohs micrographic surgery (MMS) for atypical intraepidermal melanocytic proliferation (AIMP) is unknown.

OBJECTIVE

To ascertain the frequency of diagnostic change to melanoma (upstaging) and the frequency of local recurrence after MMS for AIMP. A secondary outcome was the frequency of subclinical spread (defined as the requirement for >1 stage of MMS to achieve tumor-free margins).

METHODS

Retrospective, cross-sectional study of 223 AIMP (with 92.4% located on the head, neck, hand, foot, or pretibial leg) patients treated with MMS with melanoma antigen recognized by T cells 1 (MART-1) immunostaining.

RESULTS

Upstaging to unequivocal melanoma in situ or invasive melanoma was identified in 18.8% (42/223) of all AIMP patients. The local recurrence rate was 0% (0/223) with a mean follow-up time of 2.7 years (998 days). Subclinical spread was present in 23.8% (53/223) of AIMP patients.

LIMITATIONS

Single site, retrospective design, observational study, lack of objective criteria to diagnose AIMP.

CONCLUSION

MMS with MART-1 immunostaining achieves excellent local control of specialty site AIMP and permits definitive removal of subclinical spread before reconstruction. The central debulking excision should be evaluated with formalin-fixed paraffin-embedded section staining, since a significant percentage of AIMP are reclassified as melanoma in situ or invasive melanoma.