Clinicopathological study of 47 cases of sebaceoma

Cutaneous hybrid cysts with matrical differentiation are mostly sporadic and related to CTNNB1 mutation

Recurrent mutations in the CTNNB1 or APC genes leading to the activation of the Wnt/betacatenin pathway are observed in adnexal tumors with matrical differentiation. While most pilomatricomas arise sporadically and harbor CTNNB1 mutations, cutaneous hybrid cysts combining epidermal and matrical differentiations have been mostly reported in a context of the familial adenomatosis polyposis/Gardner's syndrome related to germinal mutations of APC. The objective of this study is to understand the pathogenesis of hybrid cysts combining epidermal and matrical differentiations. The 287 cases diagnosed as pilomatricoma/hybrid cysts registered between January 1, 2015 and February 21, 2023 in the Pathology Department at Tours University Hospital Center were considered for inclusion. After diagnosis confirmation, all cases were classified as pilomatricomas or hybrid cysts. Clinical data and microscopic features of the two groups were compared. Immunohistochemical detection of the betacatenin and CTNNB1/APC genes sequencing were performed in all hybrid cysts. Among the cohort, ten cases were classified as hybrid cysts (4%). None had a personal or familial history of familial adenomatosis polyposis. The immunochemistry confirmed a betacatenin nuclear expression in the matrical component in all excepted one cases, while no nuclear accumulation was observed in the epidermal component of most hybrid cysts (n = 8, 80%). CTNNB1 mutations were detected in all hybrid cysts with interpretable sequencing data (n = 7/10). By contrast, only a variant of uncertain significance (class 3) was detected in APC in association with a pathogenic CTNNB1 mutation in one case. Hybrid cysts are rare entities consisting in 4% of the tumors analyzed in our study. Our results suggest that most hybrid cysts occur sporadically and are associated with CTNNB1 somatic mutations.

Recurrent GRHL fusions in a subset of sebaceoma: microscopic and molecular characterisation of eight cases

AIMS

Sebaceous neoplasms constitute a group of adnexal tumours, including sebaceous adenoma, sebaceoma and sebaceous carcinoma. Although mismatch repair deficiency may be observed, the nature of the genetic alterations contributing to the development of most of these tumours is still unknown. In the present study, we describe the clinical, microscopic, and molecular features of eight sebaceomas with GRHL gene rearrangement.

METHODS AND RESULTS

Among these sebaceomas, four occurred in women and four in men; the median age was 63 years (range = 29-89). The tumours were located in the head and neck area in all cases. Microscopic examination revealed a well-demarcated lesion located in the dermis with focal extension into the subcutaneous tissue (three cases). The neoplasms displayed macronodular (eight cases), cribriform (seven cases) and organoid (six cases) growth patterns, occurring in combination. The tumours were mainly composed of immature basophilic cells associated with scattered mature sebocytes. Numerous small infundibular cysts were present in seven cases. Mitotic activity was low (none/one to four mitoses/mm2). Immunohistochemistry showed positivity for androgen receptor and p63. Preserved expression of MLH1, PMS2, MSH2 and MSH6 was observed in all cases. RNA-sequencing revealed RCOR1::GRHL2 (three cases), BCL6::GRHL1 (two cases), a BCOR::GRHL2 (one case), RCOR1::GRHL1 (one case) and TLE1::GRHL1 (one case) fusion transcript. Methylation analysis demonstrated that GRHL-fused sebaceomas form an independent cluster and highlight the proximity of such tumours with poromas with folliculo-sebaceous differentiation.

CONCLUSIONS

In conclusion, we report recurrent fusions of the GRHL genes in a distinctive subset of sebaceomas harbouring infundibulocystic differentiation, a frequent organoid growth pattern and lack of mismatch repair deficiency.

Genetic Drivers in Sebaceous Neoplasms: A Review of Germline and Somatic Mutations and Their Role in Treatment and Management Strategies

Background: The efficacy of germline testing in colorectal cancer has been proven; however, germline testing in individuals with sebaceous neoplasms is less well defined. This review aims to summarize the literature on sebaceous neoplasms to date, describing the somatic tumor profiles, tumor screening methods, and personal and family history that are suspicious of a germline mutation. Sebaceous neoplasms can be attributed to a variety of etiologies, including UV exposure, immunodeficiency, germline mutations, or multifactorial influences associated with aging. Sebaceous tumors with abnormal microsatellite instability and mismatch repair deficiency are indicative of a germline mutation in 20-50% of cases, which is similar to rates found in colorectal tumors. Personal and familial history can also be suggestive of a germline etiology in these patients and should be assessed routinely, as approximately 30% of individuals with sebaceous neoplasms carry a germline mutation. We outline a strategy for the identification of individuals at risk for germline mutations, recommendations for the management of mutation carriers, and treatment options for individuals with sebaceous neoplasms. Conclusions: Sebaceous tumors are most often sporadic; however, evaluations of a germline etiology are prudent to effectively identify those at risk of additional malignancies as well as at-risk family members. Referral to genetic counseling and germline genetic testing for individuals at risk can significantly impact cancer treatment and screening in patients and their families.

Genetics of adnexal tumors: An update

Cutaneous adnexal tumors form a vast heterogeneous group that include frequent entities that are mostly benign, as well as rare tumors that are occasionally malignant. In contrast to cutaneous tumors arising from the interfollicular epidermis that develop as a result of accumulation of UV-induced DNA damage (basal cell carcinoma, squamous cell carcinoma), the oncogenesis of adnexal tumors is related to a broad spectrum of genetic mechanisms (e.g., point mutation, fusion genes, viral integration, etc.). In this setting, specific and recurrent genetic alterations have been progressively reported, and these allow better classification of these entities. For certain of them, immunohistochemical tools are now available, enabling precise integrated histological and molecular diagnosis since certain entities are linked to well-defined alterations. In this context, we aim in this review to summarize the main molecular tools currently available for the classification of adnexal tumors.

Borderline Malignant Sebaceoma of the Auricle: A Case Report

Sebaceoma is a rare benign tumor arising from the sebaceous gland of the skin. Sebaceoma often occurs on the head and neck but rarely on the ears. We present the case of a 78-year-old female patient with a two-year history of a protruding mass in her left ear. Physical examination revealed a well-circumscribed plaque in the crus of the helix of the left ear. A wide local excisional biopsy was taken, and the mass was subjected to histopathologic assessment. While the mass showed cytological findings indicating sebaceoma, it also presented malignant features architecturally and immunohistochemically. Based on these findings, the tumor was regarded as a sebaceoma of borderline malignancy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03552-4.

Sebaceoma on the nose mimicking basal cell carcinoma: Pitfalls of dermoscopy and reflectance confocal microscopy

Sebaceoma is a rare benign sebaceous tumor that usually occurs on the face and scalp. We report a case of a 3-mm solitary pink papule on the nose in an elderly woman. Dermoscopic examination showed yellow-pinkish background with a central yellow homogeneous structure, peripheral branching vessels (crown vessels), and scattered gray or reddish-brown irregular areas. Reflectance confocal microscopy (RCM) revealed tumor islands with massive dendritic cells and scattered bright fine granules in the dermis, a suspicious palisading arrangement at the periphery, and there seemed to be peritumoral dark spaces. The combined dermoscopic and RCM examination were highly suspicious for the diagnosis of basal cell carcinoma (BCC), so the lesion was excised completely, but was eventually diagnosed as sebaceoma by histopathology. This case suggests that there are some overlaps in both dermoscopic and RCM features between sebaceoma and BCC. The application of dermoscopy and RCM to the diagnosis of sebaceoma is challenging, further studies are needed in this field.

Sebaceous Tumors of the Skin: A Study of 145 Lesions From 136 Patients Correlating Pathologic Features and DNA Mismatch Repair Staining Pattern

ABSTRACT

Sebaceous neoplasms occur sporadically or in the setting of Muir-Torre syndrome. The data regarding the correlation of pathologic features and DNA mismatch repair (MMR) staining pattern in sebaceous tumors of the skin are very scanty and based on relatively small series of patients. The goal of this study was to correlate MMR staining pattern with selected morphological features in a series of 145 sebaceous neoplasms (sebaceous adenoma, sebaceoma, and extraocular sebaceous carcinoma) from 136 patients. Cystic change, intratumoral mucin deposits, squamous metaplasia in the absence of keratoacanthoma-like changes, ulceration, intratumoral and peritumoral lymphocytes (in cases without epidermal ulceration), and intertumoral heterogeneity proved to be significantly associated with MMR deficiency. Identification of any of these changes, alone or in combination, should prompt further investigation of the patient to exclude Muir-Torre Syndrome. Our study also confirms the previously published observation that the diagnosis and tumor location are significantly associated with MMR deficiency.

Androgen receptor expression in epidermal and adnexal tumours

INTRODUCTION

Androgen receptor (AR) immunohistochemistry is used in general pathology and in dermatopathology, particularly for sebaceous tumours. The goal of this study was to quantify AR expression in benign and malignant epidermal tumours and adnexal tumours.

METHODS

We studied AR expression in 301 skin lesions using standard immunohistochemistry and compared 10 trichoblastomas, 10 sebaceomas and 10 hidradenomas using 5 markers (cytokeratin 7 and 8, PHLDA1, BerEp4 and AR).

RESULTS

The rates of AR expression were: 22% in basal cell carcinomas, 3% in squamous cell carcinomas, 92% in sebaceous tumours, 10% in follicular tumours and 22% in sweat gland tumours. Benign sebaceous tumours were AR+ in 97% of cases. Only 12% of sebaceous carcinomas showed no AR staining. The immunohistochemical profiles of the comparative study were as follows: sebaceoma: AR+, CK7-, CK8-, PHLDA1-, BerEp4-; hidradenoma: AR-, CK7+, CK8+, PHLDA1+, BerEp4+; trichoblastoma: AR-, CK7-, CK8-, PHLDA1+, BerEp4+.

DISCUSSION

AR staining was positive in 92% of sebaceous tumours, including sebaceomas, in some cases indicative of Muir-Torre syndrome. AR staining is therefore highly sensitive for the diagnosis of sebaceous tumours, but it is non-specific and is best used in combination with other antibodies, notably anti-CK8 and PHLDA1, particularly to distinguish sebaceoma from hidradenoma or trichoblastoma.

Update on the pathology, genetics and somatic landscape of sebaceous tumours

Cutaneous sebaceous neoplasms show a predilection for the head and neck area of adults and include tumours with benign behaviour, sebaceous adenoma and sebaceoma, and sebaceous carcinoma with potential for an aggressive disease course at the malignant end of the spectrum. The majority of tumours are solitary and sporadic, but a subset of tumours may be associated with Lynch syndrome, also known as hereditary non-polyposis colon cancer (HNPCC) and previously referred to as Muir-Torre syndrome (now known to be part of Lynch syndrome). This review provides an overview of the clinical and histological features of cutaneous sebaceous neoplasia with an emphasis on differentiating features and differential diagnosis. It also offers insights into the recently described molecular pathways involved in the development of sebaceous tumours and their association with Lynch syndrome.

Sebaceous lesions of the skin

Sebaceous differentiation is commonly seen in cutaneous neoplasms, both in the context of lesions showing predominantly sebaceous differentiation (e.g., sebaceous adenoma, sebaceoma and sebaceous carcinoma), or as more focal sebaceous components in neoplasms with other primary lines of differentiation. Sebaceous changes can also be a component of benign cystic lesions or epidermal tumours, and sebaceous hyperplasia is commonly encountered. This review is intended to provide an overview of the cutaneous lesions with sebaceous differentiation, with a particular emphasis on facilitating histological diagnosis of neoplasms. In addition, the role of immunohistochemical studies is outlined, as well as the evaluation of potential cases of Muir-Torre syndrome.

Sebaceous Neoplasms

Sebaceous skin tumors are classified into sebaceous adenoma, sebaceoma, and sebaceous carcinoma. An additional group of cystic sebaceous tumors indicate the Muir-Torre syndrome (MTS). Cystic sebaceous tumors are considered as morphologic variants of the 3 main categories. Multilineage adnexal tumors with partly sebaceous differentiation may pose a challenge to categorize. Sebaceous hyperplasia and nevus sebaceus are not considered as true sebaceous tumor entities. Recently, attention has been drawn to morphologic clues of sebaceous differentiation. Immunohistochemistry using the mismatch repair proteins and/or genetic microsatellite instability testing should be performed on sebaceous neoplasms to diagnose MTS as early as possible.

[Muir-Torre syndrome and Turcot syndrome]

INTRODUCTION

Lynch syndrome (LS) is a syndrome that carries a genetic predisposition to certain cancers associating, either in a single individual or in a family, a visceral tumour, mainly colorectal, with a high risk of other synchronous or metachronous cancers. LS is linked with mutations in the genes coding for proteins in the DNA repair system. Phenotypic variants of SL exist, including Muir-Torre syndrome (MTS) and Turcot syndrome (TS), both of which predispose to colorectal cancer. They may be distinguished by the presence of benign or malignant sebaceous tumours in MTS, and tumours of the central nervous system in TS.

PATIENTS AND METHODS

A 59-year-old man, with a history of right colon cancer at the age of 36 years, consulted for a nose lesion shown by histopathological examination to be a sebaceous tumour. Immunohistochemistry revealed loss of expression of proteins MSH2 and MSH6, strongly suggesting a diagnosis of MTS. Eight years earlier, the man's son had developed a fatal glioblastoma; given the paternal phenotype of MTS, the hypothesis of TS in the son is probable.

DISCUSSION

This case suggests that several variants of Lynch syndrome may be seen within the same family. It raises the issue of screening for cerebral tumours in patients with MTS and in their family members, even though such a recommendation does not exist; current recommendations in fact consist primarily of gastrointestinal and gynaecological monitoring.