Dermatopathology

Characterizing Malignant Melanomas Co-Occurring With Seborrheic Keratosis

Seborrheic keratoses (SK) are colloquially known as “wisdom spots” due to their frequent occurrence among older patients; however their prevalence among younger patients is rising.¹⁻² Typically they are described as flesh-colored to dark brown, verrucous, “stuck-on” papules with pseudohorn cysts evident on dermatoscopy. SKs are usually dismissed as benign and usually removed for cosmetic reasons; however sometimes malignant transformation into melanoma, may occur.³⁻⁴

Institute physicians saw 14 cases of MM arising in SK (MMaSK) and 10 cases of MM merging with SK (MMmSK) from 2012–2017. Demographic data were compared to a SK control group matched on age, sex, and site of lesion during the same time.

Melanoma arising in MMaSK is described as a co-occurrence of MM and SK characteristics in the same lesion (N = 14). MMmSK was identified if there were two separate lesions colliding (N = 10).

Clinical and Histopathologic Images of Melanoma Arising in Seborrheic Keratosis
Melanoma arising in seborrheic keratosis. Lesion on the neck of a 55-year-old male.
Melanoma arising in seborrheic keratosis. Lesion on the neck of a 55-year-old male.
Melanoma in situ arising in SK (Hematoxylin and Eosin Stain 15.0x magnification)
Melanoma in situ arising in SK (Hematoxylin and Eosin Stain 15.0x magnification)
Melanoma arising in seborrheic keratosis. Lesion on the upper extremity of a 75-year-old female.
Melanoma arising in seborrheic keratosis. Lesion on the upper extremity of a 75-year-old female.
Melanoma in situ arising in SK (Hematoxylin and Eosin Stain 18.6x magnification)
Melanoma in situ arising in SK (Hematoxylin and Eosin Stain 18.6x magnification)
Clinical and Histopathologic Images of Melanoma Merging With Seborrheic Keratosis
Melanoma merging with seborrheic keratosis. Lesion on the trunk of a 70-year-old male.
Melanoma merging with seborrheic keratosis. Lesion on the trunk of a 70-year-old male.
Melanoma in situ merging with SK (Hematoxylin and Eosin Stain 16.2x magnification)
Melanoma in situ merging with SK (Hematoxylin and Eosin Stain 16.2x magnification)
Melanoma merging with seborrheic keratosis. Lesion on the trunk of a 70-year-old male.
Melanoma merging with seborrheic keratosis. Lesion on the trunk of a 70-year-old male.
Melanoma in situ merging with SK (Hematoxylin & Eosin Stain 5.2x magnification)
Melanoma in situ merging with SK (Hematoxylin & Eosin Stain 5.2x magnification)

MMaSK most often occurred on the trunk or head and neck, while MMmSK most often occurred on the trunk. Histologically, MMaSK lesions contained pigment (100%), solar elastosis (71%), lymphocytic infiltrate (64%), papillomatosis (57%), pseudohorn cysts (57%), and hyperkeratosis (50%). Similarly, MMmSK contained pigment (90%), papillomatosis (80%), solar elastosis (70%), pseudohorn cysts (60%), hyperkeratosis (60%) and lymphocytic infiltrate (50%).

Given the prevalence of MM-SK in elderly males with prior sun damage, this population should be given special attention during annual skin examinations. Clinical perceptions may preclude the diagnosis of a potentially dangerous and life-threatening skin neoplasm.

References
  1. Jackson JM, Alexis A, Berman B, Berson DS, Taylor S , Weiss JS. Current understanding of seborrheic keratosis: prevalence, etiology, clinical presentation, diagnosis, and management. J Drugs Dermatol. 2015; 14(10):1119-1125.
  2. Rigopoulos D, Rallis E, Toumbis-Ioannou E, Christophidou E, Limas C , Katsambas A. Seborrhoeic keratosis or occult malignant neoplasm of the skin? J Eur Acad Dermatol Venereol. 2002; 16:168-170.
  3. Cascajo CD, Reichel M , Sanchez JL. Malignant neoplasms associated with seborrheic keratoses. An analysis of 54 cases. Am J Dermatopathol. 1996; 18(3):278-282.
  4. Lim C. Seborrhoeic keratoses with associated lesions: a retrospective analysis of 85 lesions. Australas J Dermatol. 2006; 47:109-113.