Toker Cells Revisited

Nipple Lesions of the Breast: An Update on Morphologic Features, Immunohistochemical Findings and Differential Diagnosis

Because of the unique anatomic structure of the nipple, a few specific breast lesions occur only at this site. Large lactiferous sinuses may be involved by inflammatory conditions such as squamous metaplasia of lactiferous ducts and ductal ectasia or be the site of uncommon superficial epithelial neoplasms such as nipple adenoma or syringomatous tumor of the nipple. Paget disease of the nipple may be secondary to intraepidermal extension of ductal carcinoma in situ in the underlying lactiferous ducts or develop from malignant transformation of Toker cells. Invasive breast cancer may also arise primarily in the nipple. Most of these conditions present as a palpable mass and/or skin changes with or without nipple discharge. Due to the delicate location and often relatively small size of nipple lesions, biopsy specimens are often superficial and fragmented, and the interpretation is challenging. Knowledge of the morphologic and immunophenotypic features of nipple lesions is essential in making the correct diagnosis. Information on the molecular alterations underpinning nipple neoplasms is currently very limited.

Toker Cell Hyperplasia in the Nipple-Areolar Complex of Transmasculine Individuals

We previously reported breast histopathologic features associated with testosterone therapy in transmasculine chest-contouring surgical specimens. During that study, we observed a high frequency of intraepidermal glands in the nipple-areolar complex (NAC) formed by Toker cells. This study reports Toker cell hyperplasia (TCH)-the presence of clusters of Toker cells consisting of at least 3 contiguous cells and/or glands with lumen formation-in the transmasculine population. Increased numbers of singly dispersed Toker cells were not considered TCH. Among the 444 transmasculine individuals, 82 (18.5%) had a portion of their NAC excised and available for evaluation. We also reviewed the NACs from 55 cisgender women who were aged <50 years old and had full mastectomies. The proportion of transmasculine cases with TCH (20/82; 24.4%) was 1.7-fold higher than cisgender women (8/55; 14.5%) but did not achieve significance (P = .20). However, in cases with TCH, the rate of gland formation is 2.4-fold higher in transmasculine cases, achieving borderline significance (18/82 vs 5/55; P = .06). Among transmasculine individuals, TCH was significantly more likely to be present in those with higher body mass index (P = .03). A subset of 5 transmasculine and 5 cisgender cases were stained for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), androgen receptor (AR), cytokeratin 7, and Ki67. All 10 cases were cytokeratin 7+ and Ki67-; 9 out of 10 cases were AR+. Toker cells in transmasculine cases demonstrated variable expression of ER, PR, and HER2. For cisgender cases, Toker cells were consistently ER+, PR-, and HER2-. In conclusion, there is a higher rate of TCH in the transmasculine than cisgender population, particularly among transmasculine individuals with high body mass index and taking testosterone. To our knowledge, this is the first study to demonstrate that Toker cells are AR+. Toker cell features display variable ER, PR, and HER2 immunoreactivity. The clinical significance of TCH in the transmasculine population remains to be elucidated.

Male Mammary Paget Disease: A Tale of 2 Contrasting Cases

Mammary Paget disease (MPD) comprises 1.45% all male breast cancers, compared with only 0.68% of all female breast cancers. Patients usually present in the fifth and sixth decades of life with ulceration, eczematous changes, discharge, bleeding, itching, and induration of the nipple and areola. Typically, there is a delay in definitive diagnosis and treatment from the onset of symptoms because most patients are initially treated for a rash. At the time of diagnosis, about half of the patients may have palpable breast mass, positive lymph nodes, or both. In this article, we present 2 cases of male MPD representing the extremes of clinical, radiologic, and histopathologic spectrum of the disease. One patient presented with a rash of the nipple of several months duration without an underlying lesion, whereas the other presented with sensitivity and pain of the nipple for 1 year and an underlying mass. Biopsies were diagnostic of MPD in both cases, and definitive surgery revealed an underlying ductal carcinoma in situ in the first case and an invasive ductal carcinoma in the second, highlighting the importance of early biopsy to initiate appropriate management.

Pre-Paget cells: Evidence of keratinocyte origin of extramammary Paget's disease

Extramammary Paget's disease (EMPD) is a carcinoma of the genital, perianal, and, rarely, axillary skin. The malignant Paget cells migrate extensively in the epidermis before invading the underlying dermis. Toker cells and keratinocytes have both been suggested as the cells of origin of EMPD. Paraffin sections of eight cases of EMPD were immunohistochemically stained for carcinoembryonic antigen, a known marker for Paget cells. The presence of carcinoembryonic antigen in some keratinocytes in all of the observed cases of EMPD suggests that EMPD originates from keratinocytes. Thus, keratinocytes containing carcinoembryonic antigen are pre-Paget cells.

Benign breast lesions that mimic malignancy

Many benign and reactive lesions of the breast show morphological overlap with malignant lesions. These benign mimics of malignancy often present diagnostic challenges to even the most experienced pathologists. This review focuses on several benign lesions of the breast that mimic malignant entities. For each of these lesions, we describe the key morphological and immunohistochemical features, potential diagnostic pitfalls, and our approach to arriving at the correct diagnosis.

Toker cells of the nipple are commonly associated with underlying sebaceous glands but not with lactiferous ducts

Aims

Toker cells are clear cells present in the squamous epithelium of the nipple of some women. In contrast to squamous epithelium, they are cytokeratin 7 (CK7) positive. The origin of these cells is not completely understood. It has been suggested that they may represent abortive glands or migratory ductal cells; and may be precursors of Paget's disease of the nipple. Our aim was to investigate the incidence and distribution of Toker cells and their relationship with lactiferous ducts.

Methods

We examined nipple sections from 100 consecutive mastectomies performed at Charing Cross hospital. New sections were stained for CK7 using the immunoperoxidase technique.

Results

Toker cells were identified in 11 cases. They were always clustered within the squamous epithelium superficial to sebaceous glands with no relationship with lactiferous ducts. Two cases in the study had Paget's disease and these were not associated with underlying sebaceous glands.

Conclusions

This study suggests that Toker cells are more likely to be developmentally related to sebaceous glands rather than lactiferous ducts. This raises doubts about the presence of a relationship between Toker cells and the common forms of Paget's disease, as the latter are commonly seen in association with ductal carcinoma in situ (DCIS) involving underlying lactiferous ducts. Toker cells, however, may be related to a less common form of Paget's disease which is not associated with underlying DCIS.

Proliferative lesions of intra-epidermal cytokeratin CAM5.2-positive cells in canine nipples

Non-keratinocyte cells with clear or vacuolated cytoplasm are frequently observed in the epidermis of canine nipples. Most of these cells express cytokeratin (CK) CAM5.2, a marker of luminal epithelial cells. The morphological and immunohistochemical characteristics of these clear cells were investigated. Nipple tissue from 36 dogs of both sexes was collected and labelled immunohistochemically for CAM5.2, CK7, CK14, CK18, CK20, α-smooth muscle actin, p63, melan-A, E-cadherin, epidermal growth factor receptor and oestrogen receptor (OR). The intra-epidermal CAM5.2(+) clear cells were present singly or as small clusters, mostly within the basal layer, in 22 dogs (61%). These cells also expressed CK7, CK18, E-cadherin and OR. Electron microscopy revealed that some of these cells had surface microvilli. Multifocal proliferative lesions consisting of these cells were observed in the nipples of four dogs. In these lesions, proliferating cells formed bilayered tubules with CAM5.2(+) inner and CK14/p63(+) outer cells. This is the first report describing intra-epidermal CAM5.2(+) clear cells, distinct from melanocytes and Merkel cells in dog nipples. These cells might arise from the luminal epithelium of the papillary duct.

The nipple: a simple intersection of mammary gland and integument, but focal point of organ function

Having glands that secrete milk to nourish neonatal offspring characterizes all mammals. We provide a brief overview of the development and anatomy of nipples and mammary glands in monotremes, marsupials, and marine mammals, and focus on the nipples and mammary glands in terrestrial eutherian species. We first classify eutherians into three groups: the altricial, precocial, and arboreal types based on their rearing system. We then summarize the physiology of lactation and the cell biology of nipples with specific focus on comparing these in the mouse, cow, and human, which represent the three different groups. Finally we propose that the nipple is an example of specialized epidermis. As specialized epidermis, it is dependent the underlying stroma for development and maintenance in adult life. The development of the nipple and signaling pathways that regulate its formation are described.

The nipple-areola complex epidermis: a prospective systematic study in adult autopsies

The prevalence of different types of clear cells and of the mite Demodex in the nipple-areola complex of adult autopsies of both sexes not suffering from breast cancer was studied in a total of 140 nipples. The epidermis of the nipple-areola complex shows squamous cells and 3 types of clear cells: Toker cells, pagetoid dyskeratosis cells, and signet ring-like cells. Toker cells were identified by standard light microscopy in 13 of 140 nipples (9.3%). Reactivity of these cells for CK7 was observed in 35 nipples (25%). They are derived from the lactiferous duct epithelium. Pagetoid dyskeratosis cells were identified in 56 of 140 nipples (40%). In 12 nipples, these cells were conspicuous (8.6%). It is suggested that the proliferation of these cells is induced by friction. Signet ring-like cells were identified in 71 nipples (50.7%). In 2 nipples, these cells were conspicuous (1.4%). They are a consequence of artefact related to formalin fixation. The prevalence of all these clear cells has no relationship with gender. Routine histopathological examination is usually enough to distinguish the characteristic features of the clear cells involving the nipple epidermis and permits differentiation of other entities with epidermal pale cells. Demodex mites were observed in 58 nipple-areola complexes (41.4%). They were more common in male nipple-areola complexes (P < 0.05). The prevalence of these mites was seen to remain steady along the years since the third decade. Demodex mites are common parasites of human nipple and are apparently of no pathologic significance.