Dermatology: Practical and Conceptual Commentary | Dermatol Pract Concept 2017;7(3):5 27 DERMATOLOGY PRACTICAL & CONCEPTUAL www.derm101.com Commentary Conceptually and practically all epithelial neoplasms can and should be classified as one of the following three categories, namely, benign lesion, carcinoma in situ and invasive carci- noma. When the term carcinoma used unmodified, such as squamous cell carcinoma, sebaceous carcinoma, adenocar- cinoma, generally means invasive carcinoma. Non-invasive carcinoma is synonymous to carcinoma in situ. The concept of carcinoma in situ was first introduced by Broders in 1932 [1] and has been accepted as a well-established term and diag- nostic category in many organ systems such as breast and skin (e.g., ductal carcinoma in situ of the breast and squamous cell carcinoma in situ of the skin). However, for unknown reasons, sebaceous carcinoma in situ (SCIS) has not yet to be recognized by many as a concept and diagnostic entity. From the first classification of neoplasms with sebaceous differen- tiation proposed by Warren and Warvi in 1943 [2], to the one by Rulon and Helwig in 1974 [3], Lever in 1949 and 1989 [4, 5], Elder et al in 1997 and 2005 [6, 7], Prioleau and Santa Cruz in 1984 [8], Troy and Ackerman in 1984 [9] and Steffen and Ackerman 1994 [10], Mehregan and Hashimoto in 1991 and 1995 [11,12] and Burgdorf in 1990 [13], McKee in 1996 and 2012 [14,15], Barnhill in 1998 [16], Maize in 1998 [17], Farmer and Hood in 2000 [18], and Weedon in editions from 2002 to 2017 [19-22], SCIS was not even mentioned in any of their classifications of sebaceous neoplasms. Beside the flat SCIS (see below for detail), which has been called by some as SCIS and considered as an exceedingly rare phenomenon, Chen was the first one who pointed out the existence of other histologic types of SCIS and proposed to establish SCIS as a concept and diagnostic entity [23-24]. Like the definition for any other type of carcinoma in situ, the definition of SCIS would be a sebaceous neoplasm with these microscopic features: (1) Architectural findings of confinement, namely, no invasive growth, indicating neoplastic cells still confined in epithe- lium (within surface epithelium, infundibular epithelium, Sebaceous carcinoma in situ as a concept and diagnostic entity Miglena K. Komforti1, Masoud Asgari2, Sheng Chen3 1 Department of Pathology, Hofstra Northwell School of Medicine, Hempstead, NY, USA 2 Department of Pathology, Wake Forest Baptist Medical Center, Winston-Salem, NC, USA 3 Departments of Pathology and Dermatology, Hofstra Northwell School of Medicine, Hempstead, NY, USA Citation: Komforti MK, Asgari M, Chen S. Sebaceous carcinoma in situ as a concept and diagnostic entity. Dermatol Pract Concept 2017;7(3):5. DOI: https://doi.org/10.5826/dpc.0703a05 Copyright: ©2017 Komforti 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. Corresponding author: Sheng Chen, MD, PhD, Departments of Pathology and Dermatology, Hofstra Northwell School of Medicine, 1991 Marcus Ave, Suite 300 Lake Success, NY 11042, USA. Tel. 844.719.7284. Email: schen@northwell.edu. Although carcinoma in situ has been accepted as a well-established concept and diagnostic category, for reasons unknown sebaceous carcinoma in situ has not been recognized yet in general pathology or dermatopathology. Such lesions have always been misinterpreted as either benign neoplasm or sebaceous carcinoma. In the present essay, we provide a convincing account supporting sebaceous carcinoma in situ as a valid concept and diagnostic entity via critical literature review and histopatho- logical assessment and illustration. Recognizing sebaceous carcinoma in situ as a valid concept and diagnostic entity will certainly help to avoid misinterpretation and subsequently under or over treat- ment of such lesions. ABSTRACT zenaidavega Sticky Note Delete period here 28 Commentary | Dermatol Pract Concept 2017;7(3):5 tiva) with no evidence of underlying sebaceous carcinoma or nodular/cystic SCIS (Figure 2). Flat SCIS can only be diag- nosed after excluding pagetoid involvement of surface epithe- lium by either underlying sebaceous carcinoma or nodular/ cystic SCIS. Flat SCIS is a rare lesion and often reported in the literature under the term of intraepithelial or epidermotropic sebaceous carcinoma [25-27]. Some authors call this variant as superficial type of sebaceous carcinoma [15]. The nodular type of SCIS is the most common type of SCIS. Nodular SCIS is located in the dermis and/or subcutis with or without surface epithelial involvement, has a mul- tilobulated (Figure 3A-C) or solid nodular configuration (Figure 4A-C). The lesion is well circumscribed with smooth border. There is no desmoplastic stromal response or any features of infiltrative growth. The cystic type of SCIS is located in the dermis and usually extends into subcutis. It consists of an encapsulated or well- defined cystic sebaceous lesion with smooth outer border lined by multiple layers of neoplastic sebocytes (Figure 5A & B). sebaceous gland, sebaceous duct, and/or follicular epithe- lium); and (2) Cytological attributes of malignancy, i.e. presence of nuclear atypia, enlarged nuclei, hyperchromasia, increase of nucleus to cytoplasm ratio, decrease of differentiation, increase of mitotic activity and necrosis in the form of individual cells or necrosis en masse. Of note, carcinoma in situ can certainly grow very large and render the original epithelial structure unrecognizable. That is often the case for ductal carcinoma in situ of the breast, which can form a palpable mass (Figure 1A & B). Thus, the histopathologic diagnosis of carcinoma in situ can still be made even the original epithelial structure is distorted or unrecognizable. Regarding the origin of sebaceous neoplasm, Kazakov et al. stated that “whereas in periorbital sebaceous lesions, it is accepted that sebaceous lesions arise from Meibomian glands and glands of Zeis, sebaceous glands elsewhere in the skin practically never appear to give rise to a sebaceous carcinoma” [25]. It is true no one knows for sure the exact origin of sebaceous neoplasm. But one can be certain that it must originate from epithelium, namely, epidermis, follicu- lar epithelium or sebaceous gland. Among these elements, it is reasonable to believe sebaceous neoplasm originates from sebaceous gland. If one accepts that ocular sebaceous neoplasm arises from sebaceous gland (Meibomian as well as Zeis glands), there is no reason to reject the notion that extraocular or cutaneous sebaceous neoplasm arises from cutaneous sebaceous gland, which is actually identical to Zeis sebaceous gland in the eyelid. SCIS has a number of different histopathologic expres- sions. In our opinion, there are three histopathologic types, namely, flat, nodular and cystic types. The flat type of SCIS refers to proliferation of malignant sebocytes within surface epithelium (epidermis or conjunc- Figure 1. (A) Normal breast tissue showing terminal duct lobules (H&E stain). (B) Ductal carcinoma in situ of breast, solid type, with central necrosis and calcifications. Note that the ductal carcinoma in situ forms expansile nodules completely distorting and effacing the original breast epithelial structure (H&E stain). [Copyright: ©2017 Komforti et al.] A B Figure 2. Sebaceous carcinoma in situ, flat type, showing prolifera- tion of atypical neopastic sebocytes within epidermis (H&E stain). [Copyright: ©2017 Komforti et al.] Commentary | Dermatol Pract Concept 2017;7(3):5 29 sebaceous differentiation published in 2009 [26]. Although this view has been accepted by some, it is not shared by many others in the field of dermatopathology. In an essay published in 2010, Chen proposed a different view and asserted that the so-called sebaceous adenoma is really SCIS based on the above-mentioned definition of SCIS [23]. On the other hand, poorly differentiated or high nuclear grade nodular/cystic SCIS is often misinterpreted as sebaceous carcinoma or so-called unclassifiable sebaceous neoplasm. Well- and moderately-differentiated nodular/cystic SCIS was called sebaceous adenoma initially by early authors [3, 28] and subsequently has been called this way by many up to this day. However, in an article published in 1998, Nus- sen and Ackerman revised this concept and stated that the so-called sebaceous adenoma is not a benign neoplasm but sebaceous carcinoma [29]. This notion was upheld by them in another article published in 1999 [30] and subsequently in the second edition of a book devoted to neoplasms with Figure 3. (A) Low power view of sebaceous carcinoma in situ, mul- tilobulated nodular type (H&E stain). (B) Intermediate power view of sebaceous carcinoma in situ, multilobulated nodular type (H&E stain). (C) High power view of sebaceous carcinoma in situ, multilob- ulated nodular type (H&E stain). [Copyright: ©2017 Komforti et al.] A B C Figure 4. (A) Low power view of sebaceous carcinoma in situ, solid nodular type (H&E stain). (B) Intermediate power view of sebaceous carcinoma in situ, solid nodular type (H&E stain). (C) High power view of sebaceous carcinoma in situ, solid nodular type (H&E stain). [Copyright: ©2017 Komforti et al.] A B C 30 Commentary | Dermatol Pract Concept 2017;7(3):5 3. Rulon DB, Helwig EB. Cutaneous sebaceous neoplasms. Cancer. 1974;33(1):82-102. 4. Lever WF. Histopathology of the Skin. Philadelphia, PA: Lippin- cott; 1949. 5. Lever WF, Schaumburg-Lever G. Histopathology of the Skin. 7th ed. Philadelphia, PA: Lippincott; 1989. 6. Elder D, Elenitsas R, Jaworsky C, Johnson Jr B. Lever’s Histopa- thology of the Skin. 8th ed. Philadelphia, PA: Lippincott-Raven; 1997. 7. Elder D, Elenitsas R, Johnson Jr B, Murphy GF. Lever’s Histopa- thology of the Skin. 9th ed. Philadelphia, PA: Lippincott-Raven; 2005. 8. Prioleau PG, Santa Cruz DJ. Sebaceous gland neoplasia. J Cutan Pathol. 1984 Oct; 11(5):396-414. 9. Troy JL, Ackerman AB. Sebaceoma. A distinctive benign neoplasm of adnexal epithelium differentiating toward sebaceous cells. Am J Dermatopathol. 1984 Feb; 6(1):7-13. 10. Steffen C, Ackerman AB. Neoplasms with Sebaceous Differen- tiation: A Method by Pattern Analysis Ackerman’s Histologic Diagnosis of Neoplastic Skin Diseases. Philadelphia, PA: Lea & Febiger; 1994. 11. Mehregan AH, Hashimoto K. Epidermal precancer, squamous cell carcinoma, and pseudocarcinoma. In: Pinkus Guide to Derma- tohistopathology. 5th ed. East Norwalk, CT: Appleton & Lange; 1991:501-521. 12. Mehregan AH, Hashimoto K, Mehregan DA, Mehregan DR. In- tradermal epithelioma. In: Pinkus’ Guide to Dermatopathology. 6th ed. Norwalk, CT: Appleton & Lange; 1995:643-644. 13. Burgdorf WHC. Tumor of sebaceous gland differentiation. In: Farmer ER, Hood AF, eds. Pathology of the Skin. Norwalk, CT: Appleton & Lange; 1990:615. 14. McKee PH, Marsden RA. Pathology of the Skin: With Clinical Correlations. 2nd ed. London, UK: Mosby-Wolfe; 1996. 15. Calonje E, Brenn T, McKee P, Lazar A. McKee’s Pathology of the Skin, (expert consult). 4th ed. Philadelphia, PA: Elsevier Saunders; 2011. 16. Barnhill RL. Textbook of Dermatopathology. New York, NY: McGraw-Hill; 1998. 17. Maize JC, ed. Cutaneous Pathology. Philadelphia, PA: Churchill Livingstone; 1998. 18. Steffen C. Neoplasms with sebaceous differentiation. In: Farmer ER, Hood AF, eds. Pathology of the Skin. 2nd ed. New York, NY: McGraw-Hill; 2000:1035-1058. For example, one of the sebaceous lesions interpreted as low-grade sebaceous carcinoma in a recent article by Kac- erovska et al. is clearly SCIS based on the photomicrographs the authors presented (well-defined lobulated lesion with no evidence of invasion; Figure 4 in that article) [31]. Other examples include five cases of sebaceous neoplasms with architectural features of benignancy and cytologic features of malignancy reported by Kazakov et al., who stated that “the classification of such lesions as sebaceoma (with atypia) or sebaceous carcinoma remains unresolved” [32]. This opinion was in contrast to that of Resnik, who reviewed the manuscript as well as glass slides of the five neoplasms under discussion and did not agree with the authors’ assessment that these lesions cannot be classified as either sebaceoma or sebaceous carcinoma [33]. In Resnik’s opinion, four out of the five cases represented sebaceous carcinoma and one sebaceoma. Kramer and Chen had yet another view. Based on the architectural features of benignancy (well-circumscription with smooth border of lobules with no invasive growth) and cytological features of malignancy (presence of nuclear atypia, increased mitotic figures including atypical ones, and necrosis), Kramer and Chen thought most if not all of the five sebaceous neoplasms presented by Kazakov et al. are actually examples of SCIS [24]. In summary, as one can see from above SCIS is a valid concept and diagnostic entity. The histopathological criteria for diagnosing such lesion are clear, precise and understand- able. Recognizing SCIS as a diagnostic entity can certainly prevent misinterpreting this kind of lesions as others, thus avoiding under or over treatment. References 1. Broders AC. Carcinoma in situ contrasted with benign penetrat- ing epithelium. JAMA. 1932; 99(20):1670-1674. doi:10.1001/ jama.1932.02740720024007 2. Warren S, Warvi WN. Tumors of sebaceous glands. Am J Pathol. 1943;19(3):441-459. Figure 5. (A) Low power view of sebaceous carcinoma in situ, cystic type (H&E stain). (B) Intermediate view of sebaceous carcinoma in situ, cystic type (H&E stain). [Copyright: ©2017 Komforti et al.] A B Commentary | Dermatol Pract Concept 2017;7(3):5 31 29. Nussen-Lee S, Ackerman AB. Sebaceous “adenoma” is sebaceous carcinoma. Dermatopathology: Practical & Conceptual. 1998; 4(1):5–14. https://www.derm101.com/dpc-archive/jan-mar-1998- volume-4-no-1/dpc0401a02-sebaceous-adenoma-is-sebaceous- carcinoma/. Accessed February 1, 2017. 30. Ackerman AB, Nussen-Lee S. Neoplasms in all organs of Muir-Torre syndrome are carcinomas: sebaceous carcinomas and squamous- cell carcinomas (keratoacanthomas) in skin and adenocarcino- mas, squamous-cell carcinomas, and transitional-cell carcinomas in internal organs. Dermatopatholology: Practical & Concep- tual. 1999; 5(4):312-318. https://www.derm101.com/dpc-archive/ october-december-1999-volume-5-no-4/dpc0504a03-neoplasms- in-all-organs-of-muir-torre-syndrome-are-carcinomas-sebaceous- carcinomas-and-squamous-cell-carcinomas-keratoacanthomas- in-skin-and-adenocarcinomas-squamous-cell-carcinomas-an/. Accessed February 1, 2017. 31. Kacerovska D, Drlik L, Slezakova L, et al. Cutaneous sebaceous lesions in a patient with MUTYH-associated polyposis mimicking Muir-Torre syndrome. Am J Dermatopathol. 2016;38(12):915- 923. 32. Kazakov DV, Kutner H, Spagnolo DV et al. Discordant architec- tural and cytologic features in cutaneous sebaceous neoplasms - a classification dilemma: report of 5 cases. Am J Dermatopathol. 2009; 31(1):31-36. 33. Resnik KS. The concepts of carcinoma in situ and carcinoma. Am J Dermatopathol. 2010; 32(8):855-856. 19. Weedon D. Weedon’s Skin Pathology. 2nd ed. New York, NY: Churchill Livingstone; 2002. 20. Weedon D. Weedon’s Skin Pathology. 3rd ed. New York, NY: Churchill Livingstone; 2009. 21. Patterson JW. Weedon’s Skin Pathology. 4th ed. Philadelphia, PA: Elsevier; 2016. 22. Johnston RB. Weedon’s Skin Pathology Essentials. 2nd ed. Edin- burgh: Elsevier; 2017. 23. Chen S. A different view: sebaceous adenoma is sebaceous carcinoma in situ. Dermatopathology: Practical & Concep- tual. 2010;16(2):16. https://www.derm101.com/dpc-archive/ april-june-2010-volume-16-no.2/dpc1602a16-a-different-view- sebaceous-adenoma-is-sebaceous-carcinoma-in-situ/. Accessed February 1, 2017. 24. Kramer JM, Chen S. Sebaceous carcinoma in situ. Am J Derma- topathol. 2010; 32(8):854-855. 25. Kazakov DV, Kutzner H, Spagnolo DV, et al. What is extraocular cutaneous sebaceous carcinoma in situ? Am J Dermatopathol. 2010; 32(8):857-858. 26. Ackerman AB, Nussen-Lee S, Tan MA. Histopathologic Diagnosis of Neoplasms with Sebaceous Differentiation. Atlas and Text. 2nd ed. New York, NY: Ardor Scribendi; 2009. 27. Currie GP, Plaza JA, Harris GJ. Intraepithelial sebaceous carcino- ma: a case report of an unusual occurrence. Am J Dermatopathol. 2014;36(8):673-676. 28. Lever WF. Sebaceous adenoma; review of the literature and report of a case. Arch Derm Syphilol. 1948; 57(1):102-111. https://www.derm101.com/dpc-archive/october-december-1999-volume-5-no-4/dpc0504a03-neoplasms-in-all-organs-of-muir-torre-syndrome-are-carcinomas-sebaceous-carcinomas-and-squamous-cell-carcinomas-keratoacanthomas-in-skin-and-adenocarcinomas-squamous-cell-carcinomas-an/ https://www.derm101.com/dpc-archive/october-december-1999-volume-5-no-4/dpc0504a03-neoplasms-in-all-organs-of-muir-torre-syndrome-are-carcinomas-sebaceous-carcinomas-and-squamous-cell-carcinomas-keratoacanthomas-in-skin-and-adenocarcinomas-squamous-cell-carcinomas-an/ https://www.derm101.com/dpc-archive/october-december-1999-volume-5-no-4/dpc0504a03-neoplasms-in-all-organs-of-muir-torre-syndrome-are-carcinomas-sebaceous-carcinomas-and-squamous-cell-carcinomas-keratoacanthomas-in-skin-and-adenocarcinomas-squamous-cell-carcinomas-an/ https://www.derm101.com/dpc-archive/october-december-1999-volume-5-no-4/dpc0504a03-neoplasms-in-all-organs-of-muir-torre-syndrome-are-carcinomas-sebaceous-carcinomas-and-squamous-cell-carcinomas-keratoacanthomas-in-skin-and-adenocarcinomas-squamous-cell-carcinomas-an/ https://www.derm101.com/dpc-archive/october-december-1999-volume-5-no-4/dpc0504a03-neoplasms-in-all-organs-of-muir-torre-syndrome-are-carcinomas-sebaceous-carcinomas-and-squamous-cell-carcinomas-keratoacanthomas-in-skin-and-adenocarcinomas-squamous-cell-carcinomas-an/