Research | Dermatol Pract Concept 2011;1(1):4 13 Signature nevi: individuals with multiple melanocytic nevi commonly have similar clinical and histologic patterns Robert M. Hurwitz, M.D.1, Larry J. Buckel, M.D.1 1Dermatopathology Laboratory, Inc., PC, Indianapolis, Indiana Key words: signature nevi, patterns Citation: Hurwitz rM, Buckel LJ. Signature nevi: individuals with multiple melanocytic nevi commonly have similar clinical and histologic patterns. Dermatol Pract Concept 2011;(1):4. http://dx.doi.org/10:5826/dpc.0101a04. editor: Harald Kittler, M.D. received: December 17, 2010; accepted: April 27, 2011; Published: october 31, 2011 Copyright: ©2011 Hurwitz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: None. Competing interests: The authors have no conflicts of interest to disclose. Both authors have contributed significantly to this publication. Corresponding author: robert M. Hurwitz, MD, Dermatopathology Laboratory, Inc., PC, 9292 North Meridian Street, Suite 210, Indianapolis, IN 46260, USA. Tel. 317.403.7572. Email: bobbyhur@aol.com. Introduction Individuals with multiple melanocytic nevi oftentimes have melanocytic nevi, usually two, with similar clinical and his- topathologic patterns that may be typical or atypical. The melanocytic nevi are known in common parlance as signa- ture nevi [1, 2]. In addition to being aware of these nevi, find- ing multiple unconventional melanocytic nevi with architec- tural pattern asymmetric and/or cellular pattern atypical helps to lend credence to the diagnosis of melanocytic nevus rather than melanoma. In order to evaluate the concept of the signature nevus we reviewed the histopathologic patterns of melanocytic nevi from patients having at least two nevi with similar histologic patterns. materials and methods Melanocytic nevi from patients with multiple melanocytic nevi having at least two with similar histologic pattern were retrieved retrospectively from the files of Dermatopathol- ogy Laboratory Inc., PC. Melanocytic nevi were classified according to their pattern as previously described (Figures 1-4) [3]. Two dermatopathologists (rMH & LJB) reviewed the nevi over an eight-month period. results Two hundred and eight melanocytic nevi from 77 patients, 59 females and 18 males, were included in the analysis. Ages of the patients ranged from 13 to 82 years with a mean of 40 years and a median of 47 years. The signature melano- cytic nevi were present on different anatomic sites (e.g., back, abdomen, face, scalp and extremity, etc.) in 51 of the patients, and on the same anatomic site in 26 patients. The 208 melanocytic nevi included 13 (17%) with three similar patterns and one (1.3%) with four similar patterns. The fre- quencies of melanocytic nevi according to histologic pattern are given in Table 1. There were 14 variable histologic pat- terns, which included the most common “melanocytic nevus, compound, keratotic, lichenoid, perivascular & interstitial Dermatology PrACTICAL & CoNCEPTUAL www.derm101.com 14 Research | Dermatol Pract Concept 2011;1(1):4 Figure 1. anatomic patterns of melanocytic nevi. A, Junctional: Sin- gle, nested melanocytes at the dermoepidermal junction and lower spinous layer. B, Compound: Single and nested melanocytes at the dermoepidermal junction, papillary dermis and/or reticular dermis. C, Intradermal: Single and nested melanocytes confined to the re- ticular dermis. Figure 4. example of melanocytic nevus diagnosis based on ana- tomic, architectural and cellular patterns. A composite of single anatomic and cellular patterns with single or multiple architectural patterns. Example: Melanocytic nevus, compound, keratotic, lichen- oid, perivascular and interstitial, typical cellular pattern. Figure 2. architectural patterns of melanocytic nevi. A, Epidermal: Prominent epidermal rete and infundibula. B, Keratotic: Prominent surface and infundibular hyperkeratosis. C, Interface: Single and nested melanocytes at the dermoepidermal junction and lower spi- nous zone. D, Lichenoid melanocytic: Single and nested melano- cytes at the dermoepidermal junction and lower spinous zone. E, Lichenoid lymphocytic: Single and nested melanocytes limited to the dermoepidermal junction and lower spinous zone associated with a patchy lymphocytic infiltration within a thickened papillary dermis. F, Wedge-shaped: Single and nested melanocytes in a “V” or wedge- shaped pattern in the reticular dermis. G, Perivascular, periadnexal: Single and small nested melanocytes around and associated with vascular and adnexal structures. H, Interstitial: Single and nested melanocytes splayed among collagen bundles in the reticular dermis. I, Nodular: Large round or oval collections of melanocytes in the dermis in the region of vascular and adnexal structures. J, Diffuse: Sheets of confluent melanocytes in the reticular dermis with little intervening stroma. K, Fascicular: Fascicles of melanocytes in the midst of collagen bundles in the reticular dermis. L, Pigmented den- dritic: Melanin-laden, pigmented dendritic melanocytes and melano- phages coupled with thickened collagen bundles. Figure 3. Cellular patterns of melanocytic nevi. A, Typical (small and monomorphous): Small, round, oval, polygonal, spindle or multinucleate melanocytes. B, Atypical (large and pleomorphic). C, Combined: Both typical and atypical melanocytes. Research | Dermatol Pract Concept 2011;1(1):4 15 pattern” (n=52) and “melanocytic nevus, junctional, epider- mal/interface pattern” (n=26), while “melanocytic nevus, nodular” was one of the least (n=2). Discussion The article Signature nevi [1] by Suh and Bolognia empha- sized 10 clinical types or patterns of melanocytic nevi. These signature nevi predominate in patients with multiple mela- nocytic nevi and share a similar clinical appearance. ricotti presented the histopathologic phenomenon of “Signature Nevi” at the 12th Joint Meeting of The International Society of Dermatopathology [2]. Likewise, we reviewed the histo- pathologic changes from biopsies of 208 melanocytic nevi taken from 77 patients over a period of eight months. Biop- sies were taken from two or more of their melanocytic nevi over four years that retrospectively had at least two similar histologic patterns, i.e., anatomic, architectural and cellular. Interestingly, included in this total number of melanocytic nevi, 13 (17%) of the patients had similar histologic patterns in three of their melanocytic nevi, and one patient had 4 sim- ilar histologic patterns. Thus, melanocytic nevi commonly have similar clinical as well as similar histologic patterns in patients with multiple melanocytic nevi, i.e., signature nevi. When one encounters a troublesome or atypical histologic pattern in one melanocytic nevus from an individual with many melanocytic nevi, e.g., architectural asymmetry and/or focal cellular atypia, it is common and expected to find other melanocytic nevi from that patient to have similar atypical histologic patterns. Melanocytic nevi have been reported to have a variety of clinical phenotypic patterns [11], and a variety of histologic anatomic (Figure 1), architectural (Figure 2) and cellular patterns (Figure 3) [3], not unlike that situation commonly found in apocrine neoplasia [4] and inflammatory skin dis- eases [5]. on occasion, an unusual melanocytic nevus will present with clinical and histologic changes that may be dif- ficult to differentiate from a melanoma (Figure 5a–c) and (Figure 6a–c). A quandary often occurs when there are his- tologic changes in pattern architectural such as asymmetry or pattern combined cellular such as focal cellular atypia [6]. These variations may be found and are expected in mela- nomas as well as in some unusual melanocytic nevi, such as signature nevi [7], nevi with the “ugly duckling” sign [8, 9], acquired nevi [10], congenital nevi, Spitz’s nevi [11, 12], dysplastic nevi [13], traumatized nevi, or those found on a “special site” such as the genitalia, perineum, thigh, umbili- cus, palm, sole, scalp and ear, etc. In addition, some atypical patterns of melanocytic nevi are classified by acronyms such as MIN [14], SAMPUS and MELTUMP [15], and eponyms such as Unna, Clark, reed, Miescher, Zitelli, Mark, Seab and Ackerman [16, 17], or too often with hazy descriptive moni- kers such as atypical nevus, dysplastic nevus with architec- tural disorder with moderate to severe cytologic atypia. The latter are often used to announce uncertainty and indecision by the pathologist as to whether the melanocytic prolifera- tion is benign or malignant. Those bewildering and evocative names unfortunately all too often bode ill for the patient and may lead to unwarranted surgical procedures, e.g. sentinel lymph node biopsy and lymphadenectomy [18]. regrettably, to date, there is no unanimity or litmus test to distinguish between those unusual and tricky clinical and histologic melanocytic nevi, or melanocytic proliferations from subtle melanomas. Sorry to say, we must alas rely upon question- able subjective clinical and histologic morphologic criteria to arrive at a definitive diagnosis, nevus or melanoma [19, 20]. In summary, we agree that awareness and knowledge of the fact that an individual with multiple melanocytic nevi is prone to have several melanocytic nevi with similar and table 1. Common Histologic Patterns and Number of Signature Nevi in 77 Patients with Multiple Melanocytic Nevi 1. Melanocytic nevus, compound, keratotic, lichenoid, perivascular & interstitial pattern (52) 2. Melanocytic nevus, junctional, epidermal/interface pattern (34) 3. Melanocytic nevus, compound, patchy lichenoid pattern (26) 4. Melanocytic nevus, intradermal, nodular, perivascular & interstitial pattern (12) 5. Melanocytic nevus, compound, keratotic pattern (8) 6. Melanocytic nevus, intradermal, perivascular & interstitial pattern (7) 7. Melanocytic nevus, compound, keratotic, perivascular-periadnexal, diffuse pattern (7) 8. Melanocytic nevus, intradermal, wedge-shaped pattern (7) 9. Melanocytic nevus, compound, lichenoid, perivascular & interstitial pattern (6) 10. Melanocytic nevus, intradermal, keratotic, perivascular & interstitial pattern (6) 11. Melanocytic nevus, compound, perivascular-interstitial & keratotic pattern (2) 12. Melanocytic nevus, nodular pattern (2) 13. Melanocytic nevus, nodular-diffuse pattern (2) 14. Melanocytic nevus, compound, perivascular & interstitial pattern (2) 16 Research | Dermatol Pract Concept 2011;1(1):4 Figure 5. melanocytic nevus, compound, lichenoid, combined cellu- lar pattern from a 4x4 mm changing nevus on the back of a 29-year- old woman. Melanocytic nevus, compound, lichenoid, combined cellular pattern from a 4x4 mm changing nevus on the back of a 29-year-old woman. There are predominately small round and oval pigmented melanocytes singly and in nests within the lower epider- mis, structure of adnexa, and thickened papillary dermis where there are prominent, elongated rete ridges. There are a few melanocytes present above the dermoepidermal junction, several melanocytes with atypical nuclei in the midst of those with increased cytoplasm and prominent pigmented melanin granules, plus a variety of irregu- larly shaped nests of melanocytes. Figure 6. melanocytic nevus, compound, lichenoid, combined cellu- lar pattern from a 3x3 changing nevus on the abdomen of the same 29-year-old woman seen in Figure 5. Melanocytic nevus, compound, lichenoid, combined cellular pattern from a 3x3 mm changing ne- vus on the abdomen of the same 29-year-old women seen in Figure 5. There are predominately small round and oval pigmented mela- nocytes within the lower epidermis and thickened papillary dermis where there are prominent, elongated rete ridges. There are a few melanocytes present above the dermoepidermal junction, several me- lanocytes with atypical nuclei, and a number of various melanocytes with abundant pale staining cytoplasm with melanin pigmented granules, in addition to several nests of melanocytes that vary in size and shape. Research | Dermatol Pract Concept 2011;1(1):4 17 13. Ackerman AB, Massi D, Nielsen TA. Dysplastic Nevus: Atypical Mole or Typical Myth? Philadelphia: Ardor Scribendi, Ltd., 1999. 14. rosai J. rosai and Ackerman’s Surgical Pathology. 9th ed. Elsevier Health Sciences: Philadelphia, 2004:172. 15. Elder DE, Xu X. The approach to the patient with a difficult me- lanocytic lesion. Pathol 2004; 36(5); 428-34. 16. Ackerman AB, Milde P. Naming acquired melanocytic nevi. Am J Dermatopathol 1992:14(5):447-53. 17. Ackerman AB. Interactive Quiz 781 and 783 (12/3/2008). Zitelli’s nevus (superficial and “deep” congenital). Web site. http://www. Derm101.com/. Accessed May 1, 2010. 18. LeBoit PE. Slouching toward the lymphatic lumen. Am J Derma- topathol 2005;27(6):548-50. 19. Hurwitz rM. Letters to the editor. Melanoma: experts disagree. Dermatopathology: Practical & Conceptual1996;2(1):10. 20. Farmer Er, Gonin r, Hanna MP. Discordance in the histopatho- logic diagnosis of melanoma and melanocytic neoplasms between expert pathologists. Hum Pathol 1996;27(6):528-31. 21. Hurwitz rM, Summerlin DJ. Malpractice: Has the rage become an inquisition? J Drugs Dermatol 2007;6(10):977. sometimes unusual clinical patterns (signature nevi) as well as common and/or unconventional histologic patterns (ana- tomic, architectural and cellular). As a result, this concept of signature nevi supports unusual findings, clinical and histo- logic, to be customary and expected in melanocytic nevi for a particular individual with many melanocytic nevi. When a melanoma is in the differential diagnosis of a lesion pig- mented, this valuable lesson may help to eliminate mistakes [21], avoid over diagnosing melanoma, and eliminate unnec- essary surgery. Thus, in the end, one will be more prone to arrive at an accurate, precise and definitive diagnosis of melanocytic nevus. acknowledgement We express our gratitude to Prof. Harald Kittler and the reviewers of Dermatology Practical & Conceptual for their time and effort in reviewing and analyzing our manuscript, and especially for their timely, critical and appropriate sug- gestions. references 1. Suh KY, Bolognia JL. Signature nevi. J Am Acad Dermatol 2009;60:508-14. 2. ricotti C. Cockerell C, Susa J, Sinkre P, Karai L. The Histopatho- logic Phenomenon of “Signature Nevi”. Abstracts presented at the 46th Annual Meeting of the American Society of Dermatopathol- ogy, october 1-4, 2009. J Cutan Pathol 2010:37:107-92. 3. Hurwitz rM, Buckel LJ, Eads TJ. Histologic patterns of melano- cytic nevi: a proposal for a new classification. J Drugs Dermatol 2007;6(5):487-92. 4. requena L, Kiryu H, Ackerman AB. Neoplasms with Apocrine Differentiation. Philadelphia: Lippincott-raven, 1998. 5. Ackerman AB. Histologic Diagnosis of Inflammatory Skin Dis- eases. Philadelphia: Lea & Febiger, 1978. 6. Ackerman AB, Cerroni L, Kerl H. Pitfalls in Histopathologic Di- agnosis of Malignant Melanoma. Philadelphia: Lea & Febiger, 1994. 7. Bolognia JL. Too many moles. Arch Derm 2006;142(2):508. 8. Grob JJ, Bonerandi JJ. The “ugly duckling”sign: identification of the common characteristics of nevi in an individual as a basis for melanoma screening. Arch Dermatol 1998;134(1):103-4. 9. Scope A, Dusza SW, Halpern AC, rabinowitz H, Braun rP, Za- laudek I, et al. The “ugly duckling”sign: agreement between ob- servers. Arch Dermatol 2008;144(1):58-64. 10. Saida T. Histogenesis of congenital and acquired melanocytic nevi: a unifying concept. Am J Dermatopathol 2006; 28(4):377-9. 11. Ackerman AB, Elish D, Shami S. “Spitz’s Nevus”: reassessment Critical, revision radical. New York, NY: Ardor Scribendi, Ltd., 2007. 12. Cesinaro MA, Foroni M, Sighinolfi P, Migaldi M, Trentini GP. Spitz nevus is relatively frequent in adults: A clinico-pathologic study of 247 cases related to patient’s age. Am J Dermatopathol 2005;27(6):469-75.