eMedicine Specialties > Dermatology > Benign Neoplasms

Seborrheic Keratosis: Differential Diagnoses & Workup

Author: Arthur K Balin, MD, PhD, FACP, Clinical Professor, Lankanau Medical Research Center, Jefferson Health System
Contributor Information and Disclosures

Updated: Jan 6, 2009

Differential Diagnoses

Acrochordon
Nevi, Melanocytic
Acrokeratosis Verruciformis of Hopf
Nevus Sebaceus
Actinic Keratosis
Pemphigus Erythematosus
Arsenical Keratosis
Premalignant Fibroepithelial Tumor (Pinkus Tumor)
Basal Cell Carcinoma
Prurigo Nodularis
Bowen Disease
Psoriasis, Guttate
Bowenoid Papulosis
Psoriasis, Plaque
Confluent and Reticulated Papillomatosis
Seborrheic Keratosis
Cutaneous Horn
Sign of Leser-Trelat
Cutaneous Manifestations of HIV Disease
Squamous Cell Carcinoma
Dermatosis Papulosa Nigra
Stucco Keratosis
Epidermal Nevus Syndrome
Warts, Genital
Epidermodysplasia Verruciformis
Warts, Nongenital
Erythroplasia of Queyrat (Bowen Disease of the Glans Penis)
Warty Dyskeratoma
Lentigo
Malignant Melanoma

Other Problems to Be Considered

Hidroacanthoma simplex

Workup

Laboratory Studies

  • No laboratory tests are needed unless the sudden appearance of multiple pruritic seborrheic keratoses occurs, which is known as the Leser-Trélat sign. This has been associated with the development of adenocarcinoma of the gastrointestinal tract,18 lymphoma, Sézary syndrome, and acute leukemia.

Imaging Studies

  • No imaging studies are needed, unless the sudden appearance of multiple pruritic seborrheic keratoses occurs (known as the Leser-Trélat sign).

Procedures

  • The shave biopsy provides histologic material for accurate diagnosis and removes the lesion in a cosmetically acceptable manner at the same time. After a shave biopsy is obtained, a curette can be used to smooth and remove any remaining keratotic material.

Histologic Findings

These lesions are raised above the skin surface, and they show a papillomatous epithelial proliferation containing horn cysts without any tendency toward malignancy. The proliferating cells are epidermal and have a basaloid appearance. The number of epidermal basal cells is greatly increased. The acanthotic pattern is the most frequent, in which a thick layer of basal cells is observed interspersed with pseudo-horny cysts. Invaginations to form keratin-filled pseudocysts are present. Some of these cells contain melanin. Hyperkeratotic seborrheic keratoses have pronounced hyperkeratosis and papillomatosis with less acanthosis. When papillomatosis is particularly prominent, the histology resembles acrokeratosis verruciformis of Hopf. The epidermis is comprised largely of squamous cells interspersed with aggregates of basaloid cells.

The reticulated or adenoid type of seborrheic keratoses contains numerous thin tracts of basaloid epidermal cells that are branched and interwoven. They have less epidermal thickening, and horn pseudocysts usually are less prominent in reticulated seborrheic keratoses. Marked hyperpigmentation is often present, and they have some histologic similarity to lentigo senilis. An acantholytic type with acantholysis also occurs and is particularly prominent in the squamous eddies of irritated seborrheic keratosis. Irritated seborrheic keratoses show a change from the basaloid keratinocytes observed in the acanthotic type, which are more mature squamous cells, to cells that are sometimes associated with mild nuclear atypia. The keratinocytes are arranged in swirls or whorls known as squamous eddies. Spindling of keratinocytes is common. Inflammatory cells are often observed intermingled with the proliferated epidermal cells.

The clonal seborrheic keratoses show well-demarcated nests of basaloid or larger squamous cells within an acanthotic seborrheic keratoses. Melanoacanthoma is a deeply pigmented seborrheic keratosis in which an acanthotic proliferation of large dendritic melanocytes is identified. It probably represents a concomitant proliferation or activation of the dendritic melanocytes and epidermal cells. Lichenoid seborrheic keratosis is an inflammatory variant. In one study of 108 seborrheic keratoses, 66% were acanthotic, 25% were hyperkeratotic, and 9% had a reticulated (adenoid) pattern. In this study, 5.5% (6/108) of the specimens contained squamous cell carcinoma and 4 of these appeared to develop within the central portion of the lesion. Also, 4 of the 6 malignancies developed in the reticulated type of seborrheic keratoses.

In irritated seborrheic keratoses, pronounced squamous metaplasia can occur, which may be misdiagnosed as basosquamous carcinoma. This phenomenon is not due to human papillomavirus.19 Human papillomavirus can be identified in the seborrheic keratoses of patients with epidermodysplasia verruciformis and in seborrheic keratosis – like lesions exhibiting bowenoid changes. These probably should be considered as condylomata rather than as true seborrheic keratoses.20,21

The histologic differential diagnosis of seborrheic keratoses includes verruca vulgaris, fibroepithelial polyp, condyloma acuminatum, acanthosis nigricans, epidermal nevus, confluent and reticulated papillomatosis of Gougerot and Carteaud, hidroacanthoma simplex,22 acrokeratosis verruciformis of Hopf, lentigo senilis, and tumor of the follicular infundibulum.

Acanthotic seborrheic keratoses may be confused with eccrine poromas, but no ductular differentiation is observed in seborrheic keratosis. Hidroacanthoma simplex can be distinguished from clonal seborrheic keratosis by the presence of ductal and cystic spaces histologically and by a lower density of Langerhans cells and fewer melanin granules in the intraepidermal nests. Verruca vulgaris can usually be differentiated from seborrheic keratoses because verruca vulgaris usually displays keratohyalin granule clumping, perinuclear vacuolization, and ectatic vessels within the papillary dermal tips.

More on Seborrheic Keratosis

Overview: Seborrheic Keratosis
Differential Diagnoses & Workup: Seborrheic Keratosis
Treatment & Medication: Seborrheic Keratosis
Follow-up: Seborrheic Keratosis
Multimedia: Seborrheic Keratosis
References
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Further Reading

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Keywords

seborrheic keratoses, seborrheic keratoses, reticulated seborrheic keratosis, dermatosis papulosa nigra, stucco keratosis, melanoacanthoma, skin tags

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Contributor Information and Disclosures

Author

Arthur K Balin, MD, PhD, FACP, Clinical Professor, Lankanau Medical Research Center, Jefferson Health System
Arthur K Balin, MD, PhD, FACP is a member of the following medical societies: American Academy of Dermatology, American Chemical Society, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American College of Nutrition, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Geriatrics Society, American Medical Association, American Society for Clinical Nutrition, American Society for Dermatologic Surgery, American Society for Laser Medicine and Surgery, American Society of Dermatopathology, College of American Pathologists, Gerontological Society of America, International Academy of Pathology, International Society for Dermatologic Surgery, Pennsylvania Medical Society, Phi Beta Kappa, Royal Society of Medicine, Sigma Xi, and Society for Investigative Dermatology
Disclosure: Nothing to disclose.

Medical Editor

Evan R Farmer, MD, Professor of Dermatology, Johns Hopkins University School of Medicine, Clinical Professor of Pathology, Virginia Commonwealth University School of Medicine; Consulting Staff, Department of Dermatology, Johns Hopkins Hospital, VCU Health Services
Evan R Farmer, MD is a member of the following medical societies: American Academy of Dermatology, American Dermatological Association, American Medical Association, American Society of Dermatopathology, and International Society of Dermatology
Disclosure: Nothing to disclose.

Pharmacy Editor

David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Chair, Department of Dermatology, Director, Dermatology Residency Training Program, Scott and White Clinic
David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa
Disclosure: 3M Pharmaceutical Grant/research funds Other; Graceway Pharmaceuticals Grant/research funds Other

Managing Editor

Warren R Heymann, MD, Head, Division of Dermatology, Professor, Department of Internal Medicine, University of Medicine and Dentistry of New Jersey
Warren R Heymann, MD is a member of the following medical societies: American Academy of Dermatology, American Society of Dermatopathology, and Society for Investigative Dermatology
Disclosure: Nothing to disclose.

CME Editor

Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University
Catherine Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

 
 
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