Upregulated MYC expression and p53 mutations may contribute to the oncogenesis of canine Meibomian gland carcinomas.

Sebaceous carcinomas of the human ocular adnexa commonly exhibit pagetoid spread, mutations in tumor-suppressor genes, and protooncogene copy number gain. Sebaceous carcinomas are rarely reported in other species, and while the Meibomian gland (MG) represents the most common ocular adnexal structure of the canine eyelid to develop neoplasia, most are clinically and histologically benign. The objective of this study was to compare molecular features of canine MG carcinomas and adenomas. Two retrospectively identified MG carcinomas were subject to immunohistochemistry and qPCR. When compared with normal glands, MYC was upregulated in benign and malignant MG neoplasms. Aberrant p53 expression was restricted to the nuclei of intraepithelial neoplastic cells in MG carcinomas. Adipophilin expression was diminished in MG neoplasms compared with the normal MG. Our findings, if confirmed in a larger cohort of cases, could suggest that MG oncogenesis in a dog may exhibit similar molecular features as their human counterparts.

TERT promoter mutation in sebaceous neoplasms.

TERT promoter (TERTp) mutations widely occur in multiple human neoplasms, and they have been related to different clinicopathological features. To date, this mutation has not been identified in sebaceous tumors. Here, we analyzed TERTp mutations in 91 sebaceous neoplasms (17 adenomas, 45 sebaceomas, and 29 carcinomas). We detected mutations in 26.7% (8 of 29) of sebaceous carcinomas by pyrosequencing and Sanger sequencing. No mutation was detected in adenomas or sebaceomas. The difference was significant between sebaceoma and carcinoma. The most frequent TERTp mutations were C228T and C250T in 37.5% (3 of 8) of mutated cases each one. The mutation was not associated with poor clinical evolution. Using NGS, 20 of 29 (68.5%) sebaceous carcinomas harbored mutations in 8 of the 30 genes analyzed (TP53, TERTp, EGFR, ATRX, PDGFRA, CDKN2A, PTEN, and ACVR1). With immunohistochemistry, only 1 of 8 (12.5%) TERTp-mutated carcinomas lacked mismatch repair (MMR) protein expression compared to 6 of 21 (31.6%) of non-mutated ones. Sebaceous carcinomas with MMR protein expression had significantly higher frequency of total mutations and TP53 and TERTp mutations than MMR protein-deficient carcinomas. In conclusion, TERTp mutation has been detected in sebaceous carcinomas, and its presence could be useful to differentiate sebaceous carcinoma from sebaceoma, a difficult histopathological challenge.

Twenty-Eight Cases of Extraocular Sebaceous Carcinoma: A Correlative Clinicopathological and Immunohistochemical Analysis of Extraocular Sebaceous Carcinomas and Benign Sebaceous Gland Tumors.

ABSTRACT: Extraocular sebaceous carcinoma (ESC) is a rare appendiceal skin tumor. In contrast to ocular sebaceous carcinoma, information about the exact cellular architecture of these lesions is scarce and the histogenesis of ESC is unknown. Here, we extend our previous study and investigate 28 extraocular carcinomas in comparison to 54 benign sebaceous tumors and 8 cases of normal sebaceous glands using a broad spectrum of antibodies against p63, several keratins, adipophilin, EMA, Ki67, androgen receptor, and mismatch repair proteins. This observational study demonstrates that p63- and K5/14-positive basaloid cells are key cells in normal sebaceous gland and in all sebaceous tumors and that these basaloid cells give rise to EMA+, adipophilin+ sebocytes, and K5/14+, K7±, K10± ductal structures. Finally, about half of ESC is associated with superficial in situ neoplasia, which provides evidence that at least part of these carcinomas arises from flat superficial in situ carcinoma. In contrast to the normal sebaceous gland, about half of all sebaceous tumors lack keratin K7. MMR protein IHC-profiles role will be discussed.

Metastatic Prostatic Adenocarcinoma in Patient With Muir-Torre Syndrome Misdiagnosed as Metastatic Sebaceous Carcinoma: Case Report and Systematic Literature Review.

Muir-Torre syndrome (MTS) is a rare autosomal dominant condition characterized by the presence of at least one cutaneous sebaceous tumor and one visceral malignancy, arising mostly from the gastrointestinal tract. We present the case of a 63-year-old man with several cutaneous and visceral neoplasias in the context of MTS, and a pelvic lymph node lesion diagnosed initially as metastatic sebaceous carcinoma, but later identified as metastasis from a newly diagnosed prostatic adenocarcinoma. Histological similarities between these 2 lesions are discussed. A systematic literature review was conducted evaluating all published cases of patients with MTS in which metastases were reported. Eighteen articles were included in the final synthesis, representing 20 patients with a total of 26 metastases. Seventeen patients (85%) exhibited metastases originating from MTS-related neoplasms, whereas only 2 patients (11%) exhibited metastases from concomitant malignancies. Of the 85% of patients with metastases from MTS-related malignancies, most originated from noncutaneous sources (78% from visceral neoplasms and 22% from sebaceous carcinomas). When stratifying according to metastases, 23 cases (88%) originated from MTS-related lesions, whereas only 3 (12%) originated from unrelated malignancies. Our findings thus demonstrate that most metastases found in MTS patients (88%) do indeed originate from MTS-related neoplasms. Nevertheless, it remains imperative that a broad differential diagnosis is maintained when assessing a novel lesion, to avoid misdiagnoses, as in the present case, with significant therapeutic and prognostic implications.

Frequent TLE1 Expression in Cutaneous Neoplasms.

TLE1 immunohistochemistry is widely used as a biomarker for synovial sarcoma. Recently, we identified TLE1 expression in a subset of melanomas and noted staining in sebaceous glands and follicular epithelium. TLE1 immunohistochemistry has not been well studied in cutaneous tumors. The aim was to investigate TLE1 expression in sebaceous neoplasms, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) to determine whether the staining patterns may aid in the diagnosis or classification of these neoplasms. TLE1 immunohistochemistry was performed on sebaceous adenoma (n = 26), sebaceoma (n = 10), sebaceous carcinoma (n = 19), BCC (n = 20), and SCC (n = 19). Positivity was defined as dark-brown nuclear staining and graded as 3+ (strong staining of >50% of cells at 4×), 2+ (moderate staining of 10-50% of cells at 4× or >50% of cells staining at 10×), and 1+ (weak staining of <50% of cells at 10×). No staining was scored as 0. A score of 2-3+ was considered positive and 0-1+ negative. Nuclear TLE1 expression was identified in 25/26 (96%) sebaceous adenomas, 8/10 (80%) sebaceomas, and 17/19 (90%) sebaceous carcinomas. TLE1 also labeled 19/20 (95%) BCCs and 12/19 (63%) SCCs. TLE1 immunohistochemistry frequently highlights sebaceous neoplasms, BCC, and SCC with a fairly high sensitivity (63%-96%). Therefore, TLE1 is not a specific biomarker for synovial sarcoma and should be evaluated with caution, particularly in cases in which the differential diagnosis may include other cutaneous tumors. In addition, TLE1 does not seem to be useful in the diagnosis or classification of these neoplasms.

Sebaceous Carcinoma in Situ Masquerading Clinically and Histologically as Paget Disease of the Breast.

Sebaceous carcinoma in situ is a poorly understood and ill-defined entity. In situ sebaceous carcinoma exhibits a similar location pattern to its invasive counterpart in that most commonly has a periorbital distribution. Review of the literature found only seven cases of extraocular sebaceous carcinoma in situ. We present a unique and challenging case of sebaceous carcinoma in situ masquerading both clinically and histologically as Paget's disease of the breast. A 61-year-old female presented to her dermatologist complaining of a 6 mm erythematous waxy papule on her medial right breast. The patient's past medical history was significant for Muir-Torre syndrome. Clinically, the differential diagnosis included Paget disease of the breast, squamous cell carcinoma, and sebaceous carcinoma. A shave biopsy revealed an atypical proliferation of large single cells limited to the epidermis infiltrating in a pagetoid pattern, as well as cohesive nests of round neoplastic cells with mild nuclear atypia, prominent nucleoli, and vacuolated cytoplasm. Histologically, the differential diagnosis included Paget's disease of the breast, squamous cell carcinoma in situ, melanoma in situ, and sebaceous carcinoma in situ. A battery of immunohistochemical stains was performed including CK7, EMA, CAM5.2, CK20, and MART-1. The lesional cells were positive for adipophilin, factor XIIIa, CK7, and EMA and were negative for CAM5.2, CK20, and MART-1 supporting a diagnosis of sebaceous carcinoma in situ. Multiple deeper sections were examined and invasion beyond the epidermis was not identified. This case adds to the paucity of information available regarding extraocular sebaceous carcinoma in situ and warns clinicians of this potential diagnostic pitfall especially in patients with Muir-Torre syndrome.

Pigmented trichoblastoma developed in a sebaceous nevus: HRAS mutation as a common molecular driver.

A 40-year-old woman presented with a pigmented nodule on a previously existing yellowish, verrucous plaque on the scalp. The histological diagnosis was consistent with a pigmented trichoblastoma developed within a sebaceous nevus (SN). A multigene hotspot mutational profiling of the BRAF, NRAS, HRAS and KRAS genes was carried out, and a shared G13R HRAS mutation in both the trichoblastoma and the sebaceous nevus components was found. These data support a common molecular landscape of the two lesions.

Carcinoid-Like/Labyrinthine Pattern in Sebaceous Neoplasms Represents a Sebaceous Mantle Phenotype: Immunohistochemical Analysis of Aberrant Vimentin Expression and Cytokeratin 20-Positive Merkel Cell Distribution.

This study investigated the nature of carcinoid-like, labyrinthine, rippled, and conventional cell arrangements in sebaceous neoplasms, focusing on vimentin expression and Merkel cell distribution in sebaceous neoplasms relative to these findings in normal sebaceous units and other sebaceous conditions. Immunohistochemistry for vimentin and cytokeratin 20 (CK20) was evaluated in carcinoid-like (n = 2), labyrinthine (n = 4), rippled (n = 3), and conventional (n = 6) sebaceomas; sebaceous mantle hyperplasia (n = 1); steatocystomas (n = 5); fibrofolliculomas (n = 4); sebaceous mantleoma (n = 1); sebaceous gland hyperplasias (n = 4); sebaceous adenomas (n = 4); and sebaceous carcinomas (n = 4) as well as normal skin tissue. The sebaceous mantle and its hamartoma (fibrofolliculoma) showed weak positivity for vimentin in the basal layer of the epithelial component and contained a few CK20-positive Merkel cells within the epithelial component, whereas mature sebaceous lobules were negative for vimentin and did not contain any Merkel cells. All sebaceomas with carcinoid-like or labyrinthine pattern highly expressed vimentin. CK20-positive Merkel cells were distributed with varying numbers in carcinoid-like pattern (2/2) and labyrinthine pattern (3/4) sebaceomas, sebaceous mantle hyperplasia (1/1), steatocystomas (3/5), fibrofolliculomas (3/4), and sebaceous mantleoma (1/1). Vimentin expression and Merkel cell distribution were observed in normal sebaceous mantles and sebaceous mantle-associated lesions, which could be evidence of a sebaceous mantle nature in the limited setting of sebaceous lesions. Furthermore, carcinoid-like/labyrinthine pattern sebaceomas also showed vimentin immunoreactivity and contained Merkel cells. Therefore, carcinoid-like/labyrinthine pattern of cell arrangement in sebaceous neoplasms may represent a morphological phenotype of sebaceous mantles.

Sebaceous lymphadenoma of the thymus: A clinicopathologic and immunohistochemical study of 2 cases.

Two cases of primary sebaceous lymphadenoma of the thymus are presented. The patients were a man and a woman 58 and 77 years old, respectively. The female patient had a history of breast carcinoma and on follow-up was identified to have an anterior mediastinal mass; the male patient did not have any history of malignancy, and the tumor was discovered during a chest radiographic evaluation when the patient presented with symptoms of fatigue, chest pain, and dyspnea. Histologically, both lesions were characterized by the presence of solid-cystic epithelial islands in a prominent lymphocytic background. The epithelial islands were haphazardly distributed in the form of small tubular structures with focal keratinization and groups of epithelial cells with clear cytoplasm, round nuclei and lack of mitotic activity in keeping with sebaceous cells. The presence of germinal centers in the lymphoid background was seen in both cases. Immunohistochemically, the epithelial component was positive for cytokeratin 8 (CAM5.2), cytokeratin 5/6, and for adipophilin in the sebaceous component. B- and T-cell markers were positive in the lymphoid component. Clinical follow-up in both patients showed that the 2 patients were well and alive 3 years after diagnosis. The cases herein presented expand the spectrum of salivary gland-type tumors in the mediastinum and raise awareness of lesions which are easily confused with other more common thymic tumors that have different prognosis and treatment implications.

Sebaceous carcinoma of the breast: report of four cases and review of the literature.

Sebaceous carcinoma of the breast is an exceedingly rare neoplasm. Little is known about the behavior and prognosis of this type of breast cancer. We report clinical, histological and immunohistochemical features of four cases of breast carcinoma with prominent (at least 50%) sebaceous differentiation. The tumors occurred in four women, aged 25-66, and were composed of cords, lobules and solid sheets of tumor cells with sebaceous differentiation, comprising 50-90% of the tumor mass. The second component consisted of cells with non-vacuolated cytoplasm, present mostly around the periphery of the lobules, or which formed separate tumor sheets with no evidence of sebaceous differentiation and were indistinguishable from a classical ductal carcinoma. Immunohistochemically, three tumors expressed hormone receptors; all cases were HER2-negative and had retained expression of the DNA mismatch repair proteins. Three patients had axillary lymph node metastases, and two patients had distant metastases: one in the liver, lung and bones, and one in the mediastinal and supraclavicular lymph nodes. One patient died 28 months after diagnosis, indicating that mammary sebaceous carcinoma is a potentially aggressive neoplasm. In contrast to extraocular cutaneous sebaceous carcinomas, mammary sebaceous carcinoma is probably unrelated to Muir-Torre syndrome. It should be differentiated from morphologically similar but biologically distinct lipid-rich carcinoma.

Diagnostic utility of adipophilin immunostain in periocular carcinomas.

PURPOSE: To determine the efficacy of adipophilin immunohistochemistry in the diagnosis of sebaceous carcinoma of the ocular adnexal region and to provide the guidelines for interpretation of this immunostain. DESIGN: Retrospective, histopathologic case series. PARTICIPANTS: A total of 25 patients with sebaceous carcinoma, 21 patients with basal cell carcinoma, 22 patients with conjunctival squamous cell carcinoma, 9 patients with cutaneous squamous cell carcinoma, and 5 patients with conjunctival mucoepidermoid carcinoma. METHODS: Immunohistochemical staining for adipophilin was performed on paraffin-embedded tissues and correlated with hematoxylin-eosin, periodic acid-Schiff (PAS), and mucicarmine-stained preparations. Immunostaining was quantified by light microscopy and with a computerized image analysis system of scanned images. Statistical analysis was performed to compare immunostaining patterns within the tumor categories by stage and grade, between the different neoplasms, and for correlation between light microscopy observations and computerized image analysis. MAIN OUTCOME MEASURES: Localization of adipophilin immunostain, intensity of immunostaining, percent of immunoreactive cells, percentages of vacuolar staining and granular staining, and vacuole size. RESULTS: Adipophilin expression was observed in 100% of sebaceous carcinomas, 100% of cutaneous squamous cell carcinomas, 95% of basal cell carcinomas, 73% of conjunctival squamous cell carcinomas, and 60% of mucoepidermoid carcinomas. Sebaceous carcinomas demonstrated significantly stronger adipophilin expression, a greater number of intracytoplasmic vacuoles, and larger vacuoles. The specificity and sensitivity of adipophilin immunostaining in the diagnosis of sebaceous carcinoma were both 100% when more than 5% of the staining occurred in vacuoles (<95% granular staining). The diagnostic sensitivity and specificity were 100% and 96%, respectively, when the staining was graded as moderately or strongly intense and were 92% and 85% when the vacuoles were greater than 1.5 µm in diameter. CONCLUSIONS: Although upregulation of neoplastic steatogenesis is observed in both sebaceous and nonsebaceous carcinomas, the pattern and intensity of adipophilin immunostaining are helpful in distinguishing sebaceous carcinoma from other neoplasms with overlapping histology.

Intraepithelial sebaceous carcinoma: a case report of an unusual occurrence.

Sebaceous carcinoma is a malignant neoplasm that occurs most commonly in the periorbital area, usually the eyelid. Its periocular location predisposes to smaller biopsies, thus complicating diagnosis. The neoplasm tends to exhibit aggressive local behavior, metastasizing to regional lymph nodes, and distant organs. Disease limited to the epithelium is rare, with less than 10 cases reported in the literature. We present the case of a 73-year-old woman who presented with left upper eyelid entropion and conjunctival erythema. Multiple punch biopsies showed an intraepithelial proliferation of atypical basaloid cells with enlarged and hyperchromatic nuclei intermingled with vacuolated cells containing bubbly cytoplasms and scalloped nuclei, consistent with a diagnosis of intraepithelial sebaceous carcinoma. After subsequent orbital exenteration and histological examination, a wide intraepithelial sebaceous component was identified; however, there was no invasive growth. This case highlights the rarity and the potential diagnostic pitfalls of intraepithelial sebaceous carcinoma.

Immunolabeling pattern of cytokeratin 19 expression may distinguish sebaceous tumors from basal cell carcinomas.

BACKGROUND: Distinction between sebaceous tumors and basal cell carcinomas can often pose diagnostic problems. Recent work with the antibody to cytokeratin 19 (CK 19) has shown that this marker has high specificity for undifferentiated basaloid cells. Our aim was to evaluate the use of CK 19 staining patterns in differentiating between sebaceous tumors and basal cell carcinomas. The sebaceous tumors that were examined in this study included sebaceous adenomas, sebaceous epitheliomas (sebaceomas) and sebaceous carcinomas. METHODS: Thirty-seven cases including 5 sebaceous adenomas, 16 sebaceous epitheliomas, 6 sebaceous carcinomas and 14 basal cell carcinomas (7 being of the morpheaform type and 7 nodular basal cell carcinomas) were tested with a monoclonal mouse antibody to human CK 19. RESULTS: CK 19 was focally positive in 1/5 (20%) sebaceous adenomas, 8/16 (50%) of sebaceous epitheliomas and 1/6 (17%) of sebaceous carcinomas. Strongly positive expression of CK 19 was not seen in any of the sebaceous adenoma, sebaceous epithelioma or sebaceous carcinoma specimens. CK 19 was found to be strongly positive in 9/14 (64%) and focally positive in 2/14 (14%) of basal cell carcinomas. CONCLUSION: CK 19 expression can be helpful in differentiating sebaceous tumors (including sebaceous adenomas, sebaceous epitheliomas and sebaceous carcinomas) from basal cell carcinomas and may be a useful adjunct when these entities are included in the differential diagnosis.