SKIN 
 

March 2019     Volume 3  Issue 2 
 

Copyright 2018 The National Society for Cutaneous Medicine 157 

RISING DERM STARS® 
 

 
Atypical Intraepidermal Melanocytic Proliferation – But now what? 
 
Shira Wieder, MD, Matthew Goldberg, MD, Rajendra Singh, MD 
 
1Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, NY 
 

 
 
Background/Objectives: Atypical 
Intraepidermal Melanocytic Proliferation 
(AIMP) is a descriptive histopathologic term 
that has alternative meanings at different 
institutions. It can include atypical lentigines 
or evolving/early dysplastic junctional nevi as 
well as melanoma in situ (MIS) but whose 
features are insufficient for a diagnosis of 
melanoma.1 This leads to inconsistent 
management recommendations. Our 
surveys of expert dermatopathologists about 
how these types of lesions are handled at 
other institutions yielded extensive variability 
in the definition of AIMP. This underscores 
the urgent need to better understand this 
entity. 
 
Methods: In this retrospective study, a 
cohort of AIMP cases was selected. All cases 
were limited to the year 2008 so that longer 
follow up data could be collected.  
 
Results: A total of 529 cases were 
evaluated, 312 met inclusion criteria. 
Females outnumbered males 2:1. The 
majority of AIMP’s were located on areas of 
the body with intermittent sun exposure 
(back, lower legs, arms, chest). The 
differential diagnosis listed by the clinician 
was “atypical junctional nevus” (or variants 
that included the words “atypical” or 
“dysplastic”) in 70.0% of cases followed by 
“melanoma” in only 7.9% of cases (Figure 1). 
Of the 312 cases of AIMP, 5 (1.6%) were 

found to be melanoma on re-excision. Of 
these, 4 (80%) were on maximally sun-
exposed areas (face/scalp or ears). For the 
differential diagnosis, clinicians included 
“melanoma” in 3/5 of the cases (60%). For all 
319 patients, all subsequent biopsies 
performed between 2008 to 2017 were 
looked at to see if any had occurred in the 
same location as the previous AIMP’s. 2/312 
(0.64%) of cases had the same location 
identified as the site of the previous AIMP’s 
suggestive of progression to melanoma.  
 
In addition, 14 cases that were determined to 
be AIMP at the author’s institution were 
scanned using whole slide imaging (WSI) 
and an online digital slide platform. They 
were sent to expert dermatopathologists 
across the United States and internationally. 
Each dermatopathologist read the cases as 
they would at their own institution. These 
results were divided into 3 categories: 
benign, uncertain and malignant (Figure 2). 
The discrepancy between the 
dermatopathologists was astounding and 
demonstrated the value of this research.  
 
Conclusion: In conclusion, AIMP is a poorly 
researched entity and when used in practice, 
has significant impact on patient care. One of 
the most significant suggestions made by the 
data is that AIMP found on sun-exposed 
areas may warrant re-consideration as a 
lentigo maligna. Another important 



SKIN 
 

March 2019     Volume 3  Issue 2 
 

Copyright 2018 The National Society for Cutaneous Medicine 158 

implication made by this data is that few 
AIMP’s progress over time to become 
melanoma. This has important implications 
for patients and their care. 
 
Figure 1. The differential diagnoses included 
by clinicians with the biopsies of lesions that 
were read as Atypical Intraepidermal 
Melanocytic Proliferation by 
dermatopahtologist’s at the author’s 
institution.  
 
 

 
Figure 2. 14 cases of AIMP were sent as 
whole slide digital images to expert 
dermatopathologists across the United 
States and internationally. The diversity of 
opinion is displayed below.  

 

References: 
1. Zhang, Junqian, et al. “Diagnostic 

Change From Atypical Intraepidermal 
Melanocytic Proliferation to Melanoma 
After Conventional Excision: A Single 
Academic Institution Cross-Sectional 
Study.” Dermatologic Surgery, vol. 42, 
no. 10, 2016, pp. 1147–1154 

 

0%

20%

40%

60%

80%

100%

Unknown

Malignant

Uncertain

Benign