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. 2019 Jan;80(1):178-188.e3.
doi: 10.1016/j.jaad.2018.08.028. Epub 2018 Aug 28.

Clinical spectrum of cutaneous melanoma morphology

Nikolai Klebanov  1 , Nicole S Gunasekera  1 , William M Lin  2 , Elena B Hawryluk  2 , David M Miller  3 , Bobby Y Reddy  4 , Mitalee P Christman  1 , Derek Beaulieu  1 , Suvithan Rajadurai  1 , Lyn M Duncan  5 , Arthur J Sober  2 , Hensin Tsao  6
Affiliations

Clinical spectrum of cutaneous melanoma morphology

Nikolai Klebanov et al. J Am Acad Dermatol. 2019 Jan.

Abstract

Background: Melanoma can mimic other cutaneous lesions, but the full spectrum and prevalence of these morphologic variants remain largely unknown.

Objective: To classify nonacral cutaneous melanomas into distinct morphologic clusters and characterize clusters' clinicopathologic features.

Methods: All pathologic melanoma diagnoses (occurring during 2011-2016) were reviewed for routine prebiopsy digital photographs (n = 400). Six dermatologists independently assigned lesions into 1 of 14 diagnostic classes on the basis of morphology. Image consensus clusters were generated by K-means; clinicopathologic features were compared with analysis of variance and χ2.

Results: Five morphologic clusters were identified: typical (n = 136), nevus-like (n = 81), amelanotic/nonmelanoma skin cancer (NMSC)-like (n = 70), seborrheic keratosis (SK)-like (n = 68), and lentigo/lentigo maligna (LM)-like (n = 45) melanomas. Nevus-like melanomas were found in younger patients. Nevus-like and lentigo/LM-like melanomas tended to be thinner and more likely identified on routine dermatologic examinations. NMSC-like melanomas were tender, thicker, more mitotically active, and associated with prior NMSC. Typical and SK-like melanomas had similar clinicopathologic features.

Limitations: Cluster subdivision yielded diminished sample sizes. Visual assignment was performed without clinical context.

Conclusion: When primary cutaneous melanomas were assigned into diagnostic groups and subjected to novel consensus clustering, recurrent morphologic patterns emerged. The spectrum of these morphologies was unexpectedly diverse, which might have implications for visual training and possibly clinical diagnosis.

Keywords: diagnostic accuracy; early diagnosis; education; melanoma; melanoma appearance; melanoma mimics; morphology; nevi; pigmented lesions; unusual-appearing melanoma.

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Conflict of interest statement

Conflict of Interest Disclosure: None declared for all authors.

Figures

Figure 1.
Figure 1.
Distribution of morphological assignments of 400 digital images by six board-certified dermatologists. Five morphological clusters (typical, nevus-like, amelanotic/NMSC-like, SK-like, and lentigo/LM-like) were derived using an unsupervised K-means clustering algorithm. Depth of color corresponds to assignment percentage. A dendrogram representation of relationships between individual assignments was produced by unsupervised hierarchical clustering using Ward algorithm with Manhattan distances, and revealed close relation between solar lentigo-lentigo maligna, dermal nevus-amelanotic melanoma-AK-SCC-BCC-compound nevus-other, and SK-DN. Pigmented melanoma represented a unique dendrogram branch.
Figure 2.
Figure 2.
Malignant melanoma. Representative images are included to illustrate five distinct melanoma morphological clusters identified by “consensus clustering.”
Figure 3.
Figure 3.
Clinical comparisons of melanoma morphological clusters. A. Nevus-like melanomas (CL2) were diagnosed at a significantly younger age than melanomas of other morphologies. B. Nevus-like and lentigo/LM-like melanomas (CL2 and 5) were more likely to be initially noted by a dermatologist, while typical and amelanotic/erythematous/keratotic melanomas were often initially noted by the patient or a family member. C. Typical and nevus-like melanomas were most often located on the trunk, amelanotic/NMSC-like melanomas favored the upper limb, and lentigo/LM-like melanomas favored the head and neck.
Figure 4.
Figure 4.
Pathological comparisons of melanoma morphological clusters. A. Superficial spreading melanoma was the most common pathologic diagnosis for all clusters other than lentigo/LM-like (CL5), which commonly revealed lentigo maligna melanoma. Nodular and other (desmoplastic, spindle, nevoid) melanoma was most common among the amelanotic/NMSC cluster (CL3). B. Nevus-like and lentigo/LM-like melanomas were predominately anatomic level II or II/III, while amelanotic/NMSC-like melanomas (CL3) were anatomic level IV and higher (II+ includes II and II/III, III+ includes III and III/IV, IV+ includes IV, IV/V, and V) C. Nevus-like and lentigo/LM-like (CL2, 5) melanoma clusters were significantly thinner than typical and amelanotic/NMSC-like clusters (CL1 and 3). D. Typical and amelanotic/NMSC-like melanomas displayed significantly higher mitotic activity compared to nevus-like and lentigo/LM-like melanomas.
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