AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Benign cutaneous adnexal neoplasms with sebaceous differentiation are uncommon, difficult to classify, and, at times, controversial. The main discord concerns the diversified microscopic features that vary from well-differentiated to poorly differentiated varieties. A spectrum of morphologic features can be encountered within the same neoplasm. Most reports contain few cases. Large series of cases for comparison and follow-up have been recorded.

Because of the intimate association of sebaceous glands with other adnexal structures in the folliculosebaceous-apocrine unit, many sebaceous neoplasms display complex histopathologic features with mixed sebaceous, pilar (hair), and sweat gland differentiations. Therefore, the term sebaceous neoplasms is necessary to include these complex skin adnexal tumors with varying degrees of sebaceous differentiation. The term sebaceous neoplasms includes benign and malignant tumors with different degrees of sebaceous differentiation. The following terms are recognized within this category: sebaceous adenoma (SA), sebaceous epithelioma (sebaceoma), sebaceous carcinoma, basal cell carcinoma with sebaceous differentiation, sebocrine adenoma, and sebomatricoma.

Skin lesions containing benign sebaceous gland proliferation (eg, sebaceous hyperplasia), congenital hamartomas (eg, nevus sebaceus), and lesions with ectopic sebaceous structures (eg, Fordyce spot, Montgomery tubercles) are generally not considered to be true sebaceous neoplasms.¹

When patients with numerous SAs and/or other neoplasms with sebaceous differentiation have an associated internal malignancy, the condition is called Muir-Torre syndrome.

Pathophysiology

The sebaceous gland is a secreting structure consisting of sebaceous lobules and ducts. Although it is a glandular adnexal structure, the sebaceous gland is topographically and ontogenetically related to the hair sheath. Therefore, antigenic similarities exist between the isthmus of the outer hair sheath and the germinative basaloid cells of the sebaceous gland. Sebaceous glands are most abundant in the skin of the head and neck regions, but they are also present throughout the hair-bearing areas of the body. The eyelids have modified sebaceous glands (ie, Zeis glands of cilia associated with eyelashes, meibomian glands within the tarsal plates of the upper and lower eyelids).

Ectopic sebaceous glands are not associated with hair follicles. Known as Fordyce condition, they commonly occur on the vermilion border of the lips and on the buccal mucosa of adults. These structures are not considered sebaceous neoplasias.

As one of the skin's adnexal structures, the sebaceous gland is intimately associated with hair (pilar) and arrector pili muscle. Because of the intimate association of sebaceous glands with hair and apocrine ducts, many sebaceous neoplasms display complex histopathologic features with varying elements of pilar and sweat gland differentiation.

Pilar and sebaceous neoplasms share common expression for both high and low molecular weight cytokeratin but not most eccrine or apocrine tumors, pointing to similar cellular differentiation patterns of hair and sebaceous structures. Furthermore, the architectural features of sebaceous tumors bear resemblance to those of pilar neoplasms, and not to sweat gland tumors. Many antigens associated with sweat gland neoplasms, including S-100 protein, CA72.4, gross cystic disease fluid protein 15 (GCDFP-15), and carcinoembryonic antigen (CEA), are absent in sebaceous tumors.²

Mature sebocytes express antigenicity for epithelial membrane antigen (EMA) and related substances.  Some studies have reported selective labeling of sebocytes and their neoplasms for nuclear androgen receptor protein (ARP), but with some contradictory results. Reactivity for immunoglobulin A, lipase, milk fat globule–associated (ovarian carcinoma–associated) sebaceous antigen OV-2, and OKM5 (CD36) antigen may be selective for sebaceous lesions.^{3, 4, 5}

All sebaceous glands are derived from the embryonal stratum germinativum (epidermal basal layer), which give rise to the epidermis and epidermal appendages.

During the 13-15th weeks of intrauterine life, part of the primary epithelial germ develops into pilosebaceous pegs; later, their outgrowths form hair and sebaceous glands. Sebaceous glands are found next to hair follicles and arrector pili muscles. From the 15-20th weeks of gestation, the most superior bud on the primitive pilosebaceous germ develops into the apocrine gland, which is a specialized sweat structure. These integral structures are known as folliculosebaceous-apocrine units. Development of sebaceous glands begins in the scalp and the face at the beginning of the second trimester (80-mm stage) and progresses in a cephalo-caudal direction.

Any sebaceous gland in the body has the potential to develop into sebaceous neoplasms. These tumors are cutaneous adnexal tumors that show varying degrees of sebaceous differentiation.

SA is defined as a benign epithelial neoplasm composed of sebaceous glandlike structures or tumors with well-recognized sebaceous differentiation by microscopic examination.

Frequency

United States

The exact incidence is unknown. Prior to 1967, sebaceous neoplasms were regarded as rare solitary tumors; only a few publications reported them. However, in 1967, Muir and his colleagues⁶ first described the coexistence of multiple sebaceous tumors and carcinoma of the larynx and the intestine. Torre⁷ noted that a patient with multiple skin neoplasms showing sebaceous differentiation later developed carcinoma of the ampulla of Vater in the duodenum and the colon. Multiple sebaceous neoplasms in a patient may be associated with the clinical Muir-Torre syndrome. See Muir-Torre Syndrome for more information.

International

No reported increased incidence of SA has occurred in a particular geographical location.

Mortality/Morbidity

SAs are benign cutaneous adnexal neoplasms that do not possess a potential for aggressive growth or metastasis that cause fatality. Local recurrences are occasionally encountered following incomplete removal of the tumor. When multiple SAs are associated with Muir-Torre syndrome, visceral carcinomas, including adenocarcinomas of the colon, stomach, duodenum, hematologic system, genitourinary tract, endometrium, and larynx (in decreasing order of frequency) may also be present. The most significant feature of Muir-Torre syndrome is the favorable prognosis of each of these associated carcinomas. However, some of these malignancies have the potential to metastasize; fatalities due to internal malignancies have been reported.

Race

No reported predisposition is reported for any particular race.

Sex

SAs affect men and women equally.

Age

SAs frequently appear on the face or scalp of middle-aged and older individuals, after age 50 years. The mean age at onset is 60 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

History

• Patients with SAs typically experience a gradual onset of small, usually less than 0.5 cm in diameter (2-4 mm), smooth, yellow, sometimes speckled papules with central umbilication on the skin of the face or scalp over a period of several months.
• Some middle-aged and older individuals may have multiple papules (as described above) or nondescript papules on their faces or other parts of their skin surface.

Physical

• SAs range in size from less than 1 cm (usually 2-4 mm) to greater than 5 cm in maximum dimension.
• Tumors most frequently appear as a yellow, speckled, smooth-surfaced, circumscribed papule or nodule (see Media File 1).
• At times, these tumors have a polypoid appearance or central umbilication.
• SAs sometimes present as tan or pink-to-red papules.
• Tumors are commonly located on the face, the scalp, and the neck.
• Occasionally, tumors may be seen at other sites, including the trunk and the legs.
• Clinical impression is usually a basal cell carcinoma or nondescript papule without definitive clinical diagnosis prior to biopsy with histopathologic examination.

Causes

SAs form part of the spectrum of the Muir-Torre syndrome. A genetic predisposition exists in some cases of the Muir-Torre syndrome, and this syndrome has been found in association with the so-called cancer family syndrome.

• The identification of a truncating germline mutation in the mismatch repair (MMR) gene, hMLH1 or hMSH2, by DNA molecular genetic study in some patients having cystic sebaceous tumors with Muir-Torre syndrome highlights the value of recognition of cutaneous markers of internal malignancy.
• In 1999, Rütten et al⁸ studied 19 patients with Muir-Torre syndrome using DNA molecular genetic analysis and reported that 8 (42%) of these patients presented with a cystic variant of sebaceous tumors (including SAs). They concluded that cystic sebaceous neoplasm is a marker for the MMR-deficient subtype of Muir-Torre syndrome with a high risk for developing internal malignancies at a later date.
• The genetic disorder in Muir-Torre syndrome is an autosomal dominant inherited germline mutation in one of the DNA mismatch repair genes, most commonly hMSH2.⁹ It is inherited with a high degree of penetrance and variable expression, with a male-to-female ratio of 3:2. Children of a Muir-Torre syndrome individual, therefore, may have a 50% risk of inheriting the cancer predisposition. In families in which the germline mutation can be identified, those individuals who have inherited the mutation should undergo regular screening examinations, particularly of the gastrointestinal tract, colorectum, genitourinary tract, and female genital tract.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

Other Problems to be Considered

Sebaceoma
Sebocrine adenoma
Sebomatricoma
Adnexal tumor with sebaceous differentiation
Basal cell carcinoma with sebaceous differentiation
Superficial epithelioma with sebaceous differentiation

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• Appropriate laboratory testing for possible occult internal malignancies, such as gastrointestinal tract, hematologic, or laryngeal carcinomas, is indicated. The following laboratory tests can be of diagnostic value if patients present with cutaneous signs of Muir-Torre syndrome.
• • Sigmoidoscopy may be performed for screening of colonic polyposis and colonic carcinoma.
  • Perform endoscopy to check for an occult gastric carcinoma.
  • Serum carcinoembryonic antigen values are frequently increased in patients with colonic carcinomas.
  • A complete blood cell count assists in detecting hematologic malignancies.
  • A bone marrow examination may be needed to further delineate a hematologic malignancy.
  • Laryngoscopy with biopsy examination of any suspicious lesions can rule out an occult laryngeal carcinoma.

Imaging Studies

• Abdominal CT scanning and MRI assist in detecting an occult internal malignancy, such as kidney and urothelial cancers, in patients with Muir-Torre syndrome.

Procedures

• A biopsy of skin tumors performed for histopathologic examination provides an accurate diagnosis of sebaceous neoplasms, including SAs.
• Histopathologic examination of specimens obtained from polypectomy and laryngoscopy of patients with suspected Muir-Torre syndrome confirms the presence or the absence of occult internal malignancy. Peripheral blood smear, bone marrow examination, and lymph node biopsy may assist in detecting an associated hematologic malignancy in these patients.

Histologic Findings

Controversy surrounds the classification of sebaceous neoplasms. Some authors maintain that all lesions called SA are, in fact, sebaceous carcinoma. Their arguments have been largely based on histologic findings, rather than evidence concerning tumor biology or behavior. Until evidence suggests that these lesions are capable of behaving in a malignant fashion, classifying them separately from sebaceous carcinoma may be best. Complete excision of all sebaceous tumors is reasonable.

The characteristic microscopic features of classic SA are described below. The tumor is multilobulated with frequent connection to the surface epidermis, attenuating or replacing it. At low-power view, it is sharply demarcated from the surrounding tissue (see Media File 2) with a proliferation of variously sized sebaceous lobules consisting of central, larger, mature sebaceous cells (sebocytes); peripheral, smaller, undifferentiated, germinative basaloid cells (see Media Files 3-4); and transitional cells.

The sebocytes contain pale-staining, foamy-to-bubbly cytoplasm, and central, crenated, hyperchromatic nuclei. The smaller, germinative cells contain round-to-oval, vesicular nuclei and basophilic cytoplasm (see Media File 5). The transitional cells show more eosinophilic cytoplasm. The ratio of basaloid and transitional cells to sebocytes varies but is traditionally defined as sebaceous adenoma if 50% or more of the cells are sebocytes. The cellular lobules of SA sometimes comprise ductal structures with holocrine secretion, which may result in occasional cystic degeneration or formation of intralesional cysts (see Media File 6). Nuclear hyperchromatism, prominent nucleoli, and mitotic activity are rarely observed in SA lesions.

In both benign and malignant sebaceous proliferations, the characteristic "bubbly" cytoplasmic profile of the mature sebocyte is maintained.  EMA staining in these tumors is comparable to that seen in non-neoplastic sebaceous epithelium, in that cytoplasmic lipid vesicles are rimmed by EMA reactivity.

To date, specific markers of sebaceous differentiation have not been characterized.  Sebaceous and sweat gland neoplasms do share diagnostically relevant determinants, such as CD15 and BerEP4. However, using an antibody panel directed at EMA, S-100 protein, and CEA allows separation between sebaceous and sweat gland neoplasms in most instances, the former staining positive for EMA, while S-100 protein and CEA decorate sweat gland epithelium.

SA of the Muir-Torre variant tends to show more prominent cystic change, peripheral-disposed basaloid, germinative-type cells, often with mild nuclear pleomorphism, distinct nucleoli, and moderate mitotic activity. Note that patients with Muir-Torre syndrome (see Media File 6) frequently present with SA with classic histologic features of solitary tumors. No histologic features of SA could reliably pinpoint the association of Muir-Torre syndrome, but loss of nuclear staining for MLH-1 or MSH-2 is highly suggestive of the syndrome.  These tests are performed by the immunoperoxidase method.

Neoplasms with sebaceous differentiation have many and disparate morphologic features because of different degrees of differentiation within the same tumor. Thus, the classification of these tumors can sometimes be difficult and confusing, which has resulted in the usage of various histologic diagnostic terms in the literature. The differential features are listed below.

• In contrast to sebaceous hyperplasias, SAs contain mixed 2 cell types (ie, sebocytes and germinative cells). However, sebaceous hyperplasia consists of hyperplastic sebaceous lobules sebocytes (see Media File 6) and peripheral 1 or 2 cell layers of germinative epithelium that sometimes proliferates around dilated follicular ducts.
• Sebaceous carcinomas differ from SAs by the presence of dermal aggregates of markedly atypical poorly differentiated, polyhedral tumor cells separated by fibrovascular stroma. The central portion of the cell nests frequently undergoes necrosis, resulting in a comedo pattern on scanning microscopic view. The bubbly cytoplasm or intracellular compartmentalized vacuoles in sebaceous carcinoma are not as conspicuous as that seen in SAs.
• • In sharp contrast to benign SA, sebaceous carcinomas contain dermal aggregates of markedly atypical, poorly differentiated, polyhedral tumor cells separated by fibrovascular stroma.
  • The presence of tumor cells with sebaceous differentiation requires special histochemical techniques, such as oil red O or Sudan IV stains, on fresh tissue and EMA immunostains in paraffin-embedded tissue to highlight their presence.
  • Sebaceous carcinomas differ from Merkel cell carcinoma (another poorly differentiated skin cancer) in negative expression of CK20 and neuron-specific enolase (NSE) and positive EMA on immunohistochemical examination.
• Sebaceous epitheliomas share many histologic features of SAs, except for the presence of more than 50% of cells of the smaller, germinative, basaloid cells.
• Some use the term basal cell carcinoma with sebaceous differentiation as a synonym for sebaceous epithelioma because the histologic features of these lesions can be inseparable; however, the former exhibits most of the histologic criteria of basal cell carcinoma.
• Sebaceomas are benign cutaneous adnexal neoplasms with complex histologic differentiating features, including sebaceous epithelioma, trichoepithelioma, and dermal duct tumor.¹⁰
• Sebomatricoma is a term that has been suggested to include all benign tumors with sebaceous differentiation, including sebaceous hyperplasia, SA, sebaceoma, and sebaceous epithelioma.
• MLH-1 and MSH-2 immunostaining can be applied to paraffin-embedded sections. Loss of expression suggests microsatellite instability and Muir-Torre syndrome.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical Care

Recognizing the presence of sebaceous neoplasms can help identify patients with Muir-Torre syndrome; thus, early treatment of an associated occult malignancy may be initiated.

Surgical Care

Surgical treatment is aimed at completely removing the tumor and preventing regrowth of the tumorous tissue.

Consultations

Referring patients with cutaneous signs of Muir-Torre syndrome to a gastroenterologist, a hematologist, or an otolaryngologist is essential for dermatologists to rule out the presence of an occult malignant tumor.

FOLLOW-UP

Section 7 of 10  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Except for the patients with Muir-Torre syndrome, no inpatient care is recommended for patients with SA.

Further Outpatient Care

• Completely remove SAs surgically to prevent local recurrences.

Transfer

• Consulting other specialties for patients with suspected Muir-Torre syndrome is recommended to rule out the presence of an occult internal malignancy.

Prognosis

• SAs are benign tumor growths that derive from sebaceous glands. The solitary tumors are treated by complete surgical removal with a 100% cure rate. Incomplete removal has occasionally resulted in local recurrence.

Patient Education

• Advise older patients (>60 y) of the potential existence of an internal malignancy when multiple sebaceous neoplasms are present.

MISCELLANEOUS

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical/Legal Pitfalls

• Failure to recognize patients with multiple sebaceous neoplasms of the skin as a sign of an internal malignancy may delay treatment of gastrointestinal, particularly colonic, hematologic, genitourinary, endometrial, laryngeal, or other potentially aggressive neoplasms.
• Failure to perform a biopsy of the skin tumor or tumors to establish an accurate diagnosis is a pitfall.
• Failure to recommend a consultation to other specialists for workup of visceral malignancies is a pitfall.

MULTIMEDIA

Section 9 of 10  

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• Clinical
• Differentials
• Workup
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• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  A biopsy-proven sebaceous adenoma on the forehead of a 64-year-old man. The tumor appeared as a dome-shaped, elevated nodule with a circumscribed margin. It measured 8 mm in diameter, with a smooth, shiny, yellow, and specked appearance. The tumor had a history of slow growth, and the patient had noticed it for more than a year. Note the pearly appearance and the presence of a few capillaries traversing the tumor surface, a feature closely mimicking the clinical appearance of that of a basal cell carcinoma. The total surgical removal of this tumor was uneventful. The patient had not experienced a recurrence.
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Media file 2:  Low-power view of a photomicrograph of sebaceous adenoma. Note the dome-shaped elevation of the epidermal surface, the sharp circumscription from the adjacent dermal tissue, and the slight central cystic appearance with eosinophilic secretory material. Patients with sebaceous tumors showing more prominent cystic change have been found to have DNA abnormalities that are linked to a higher risk of the development of internal malignancies at a later date.
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Media type:  Photo

Media file 3:  A medium-power view of the well-differentiated SA shown in Image 1, depicting proliferation of well-differentiated sebaceous lobules with central, larger, mature sebocytes and peripheral, smaller, less-differentiated, basaloid, germinative cells. Note that the sebaceous lobules are connected to the overlying epidermis and are slightly off-center in this field; a collection of eosinophilic, pink-colored, keratinous material is present in a dilated follicular ostium within the tumor (hematoxylin and eosin, original magnification X75). In contrast to a sebaceous hyperplasia, a sebaceous adenoma such as seen in this microscopic field contains sebaceous lobules with a 2-cell type and not a single-cell type of sebocytes as seen in the former. The neoplasm was completely removed, with no known recurrences to date.
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Media type:  Photo

Media file 4:  Higher-power view of a photomicrograph of a sebaceous adenoma. Note the intermingled 2 cell types, ie, well-differentiated pale-staining sebocytes containing vacuolated (bubbly) cytoplasm and smaller, darkly stained, basaloid, less-differentiated matrix cells. An occasional mitotic figure (arrow) was present. The tumor was completely excised, and no recurrences were noted in this patient at 5-year follow-up (hematoxylin and eosin, original magnification X200).
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Media type:  Photo

Media file 5:  A close-up, higher-power view of the sebaceous adenoma in Image 4. The cytologic details are evident. Notice the predominant, larger sebocytes (arrow) containing pale-staining, bubbly cytoplasm (intracytoplasmic compartmentalization) and a few smaller, basaloid, germinative cells of pilosebaceous structures. The nuclei are vesicular without overt pleomorphism or mitotic activity (hematoxylin and eosin, original magnification X300).
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Media type:  Photo

Media file 6:  Multiple sebaceous neoplasms on the skin of the chest and the trunk of a 62-year-old man. The tumors were biopsy-proven sebaceous tumors with varying degrees of sebaceous differentiations. The patient was found to have a well-differentiated adenocarcinoma of the colon by subsequent colonoscopy, CT scan, and MRI examinations.
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Media type:  Photo

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• Multimedia
• References

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14. Lynch HT, Fusaro RM, Roberts L, Voorhees GJ, Lynch JF. Muir-Torre syndrome in several members of a family with a variant of the Cancer Family Syndrome. Br J Dermatol. Sep 1985;113(3):295-301. [Medline].
15. Misago N, Narisawa Y. Sebaceous neoplasms in Muir-Torre syndrome. Am J Dermatopathol. Apr 2000;22(2):155-61. [Medline].
16. Ollila S, Fitzpatrick R, Sarantaus L, Kariola R, Ambus I, Velsher L, et al. The importance of functional testing in the genetic assessment of Muir-Torre syndrome, a clinical subphenotype of HNPCC. Int J Oncol. Jan 2006;28(1):149-53. [Medline].
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18. Steffen C, Ackerman AB. Neoplasms With Sebaceous Differentiation. Philadelphia, Pa: Lea & Febiger; 1992.
19. Sáchez Yus E, Requena L, Simón P, del Río E. Sebomatricoma: a unifying term that encompasses all benign neoplasms with sebaceous differentiation. Am J Dermatopathol. Jun 1995;17(3):213-21. [Medline].
20. Tsalis K, Blouhos K, Vasiliadis K, Tsachalis T, Angelopoulos S, Betsis D. Sebaceous gland tumors and internal malignancy in the context of Muir-Torre syndrome. A case report and review of the literature. World J Surg Oncol. 2006;4:8. [Medline].
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Article Last Updated: Nov 29, 2007