Sebaceous mantleoma (mantle adenoma): reappraisal of the myth of the problematic benign neoplasm with sebaceous mantle differentiation

Carcinoid-Like Cell Arrangements in Basal Cell Carcinoma: A Study of 11 Cases

Background. Carcinoid-like pattern in basal cell carcinoma is extremely rare and has only been documented in a textbook. The aim of this study is to reveal the characteristics of the carcinoid-like pattern in basal cell carcinoma as well as to establish the concept of the tumor pattern. Methods. Of 355 basal cell carcinoma cases (355 lesions of 308 patients), 11 tumors with histopathological features of carcinoid-like pattern were retrieved. Results. The patients included 5 males and 6 females with a median age of 73 years (range 38-86 years). Of the 11 lesions, 10 were observed on the head. Histopathologically, a carcinoid-like pattern with branching and anastomosing of trabecular structures was observed in 30% to 95% of the tumor area. No differentiation to sebocytes was observed in any of the tumors. The tumors were well-circumscribed, although 3 lesions contained an infiltrative-type component as well. The carcinoid-like pattern areas in all 11 lesions exhibited diffuse BerEP4 immunoexpression but no KIT, synaptophysin, or vimentin expression. Keratin 20-positive Merkel cells were not observed in the tumor areas. Conclusions. Basal cell carcinoma can show a carcinoid-like pattern cell arrangement. Based on the histopathological and immunohistochemical findings from our study, we collectively conclude that the carcinoid-like pattern in basal cell carcinoma does not seem to represent sebaceous mantle differentiation. Carcinoid-like pattern basal cell carcinoma can be distinguished from other tumors by the favorite site of the head, the co-existence of conventional basal cell carcinoma components, lack of sebaceous differentiation, and diffuse BerEP4 immunoexpression.

Merkel cells in extraocular sebaceous carcinoma

INTRODUCTION

Mature sebaceous glands do not contain Merkel cells. Neither do sebaceous tumors in the vast majority of cases. Recently, however, it was showed that rare sebaceous adenomas with a carcinoid-like or labyrinthine pattern can contain intratumoral Merkel cells. Our purpose in this study is to examine for the presence of Merkel cells in extraocular sebaceous carcinomas.

METHODS

Nineteen cases of extraocular sebaceous carcinoma were retrospectively studied with cytokeratin 20.

RESULTS

One out of 19 cases (5.3%) contained Merkel cells in the basal layers of the tumoral nests of a sebaceous carcinoma from the cheek of a 76-year-old woman.

CONCLUSIONS

Merkel cells are rarely evident in extraocular sebaceous carcinoma, and therefore, their evidence does not exclude this diagnosis.

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 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.