Apocrine Encapsulated Papillary Carcinoma of the Breast: The First Reported Case with an Infiltrative Component

Controversies regarding encapsulated papillary carcinoma of the breast: an approach to evaluation and categorisation

Malignant papillary lesions, and in particular, encapsulated papillary carcinoma (EPC) of the breast, continue to present diagnostic challenges for the practising pathologist. In addition to the relative rarity of these lesions, the lack of evidence-based diagnostic criteria, differences in the biological characteristics, and the clinical behaviour of in situ and invasive forms, variable use of immunohistochemical markers, and overlap with other tumour types including high-grade circumscribed forms of invasive breast carcinomas has resulted in diagnostic discordance with potentially significant clinical and management implications. Pathologists should be familiar with the range of morphology observed in malignant papillary tumours, EPC, and EPC-like tumours and the existence of tumours with overlapping features. In this review we summarize the common diagnostic pitfalls in malignant papillary tumours and provide an approach to the diagnostic evaluation and categorisation of these enigmatic entities.

Encapsulated papillary carcinoma of the breast clinicopathological features and management: Could sentinel lymph node biopsy be exempted?

BACKGROUND

Papillary lesions in the breast pose diagnostic and therapeutic challenges. Encapsulated papillary carcinoma (EPC) is a rare breast cancer. However, evidence-based guidelines are limited. For this reason, there is no complete clarity in diagnosis and treatment management, and there are insufficient studies in the literature. This study aimed to examine the necessity of sentinel lymph node sampling in the management of EPC, in line with patients' clinicopathological data.

METHODS

We retrospectively screened patients with EPC in our clinic between January 2012 and March 2022. We recorded and statistically evaluated patients' demographic, clinical, radiological, pathological, and treatment management.

RESULTS

Sixty-four patients with EPCs were identified. The final pathologic evaluation revealed that 19 patients (18.7%) had pure EPC, 27 patients (43.7%) had EPC with associated ductal carcinoma in situ and 18 patients (37.5%) had EPC associated with invasion. The mean age was 61 years, and two patients were male. Breast-conserving surgery was performed in 62 patients, and simple mastectomy was performed in two patients. Sentinel lymph node biopsy (SLNB) was positive in only one patient. Sixty-three patients with EPC were hormone receptor-positive, and one patient was triple-negative and was associated with invasion. None of the patients died, one had a local recurrence, and a mastectomy was performed.

CONCLUSIONS

The overall prognosis and long-term survival of patients with EPC were excellent. Our study and the current literature indicate that routine SLNB is overtreatment because surgical excision with negative margins is sufficient in EPC cases and lymph node metastasis is rare, even with an invasive component.

An intriguing journey of encapsulated apocrine papillary carcinoma of the breast

Background

Encapsulated Apocrine Papillary Carcinoma (EAPC) of the breast are very rare tumors. They usually present as a cystic mass with mural nodule in women aged 44–84 years. Affected patients may be asymptomatic or complain of breast swelling, or nipple discharge. Mammographic features are nonspecific. The tumor appears as a high-density round or oval mass with circumscribed or spiculated margins on mammography. On Ultrasonography (US) a classical lesion appears as predominantly cystic mass with intracystic solid papillary projections and area of vascularity within it. Contrast Enhanced Breast MRI helps to further characterize the lesion by showing intense contrast enhancement in early phase along with washout curve. Histological features of these tumors are similar to those of classical encapsulated papillary neoplasm, in that myoepithelial cells are absent within the papillary structures and at the periphery of the cyst. They show variable degree of cytological atypia and mitotic activity. Such tumors consist of abundant granular eosinophilic cytoplasm and large nuclei with prominent nucleoli and are androgen receptor positive. However, a multidisciplinary approach is crucial for diagnosis and tissue histology is essential to suitably formulate treatment guidelines. Surgical excision is the preferred treating option for these tumors. Little consensus is available about local radiation and adjuvant therapy for the treatment of such tumors, yet they have been reported to have good prognosis.

Case presentation

This rare case report describes the intriguing journey towards the diagnosis of an encapsulated intracystic apocrine papillary carcinoma in a 52-year-old premenopausal female who presented with palpable breast swelling in left breast. The patient underwent mammography, breast ultrasound and breast MRI concluding it to be a BIRADS 4A lesion. Then the patient was subjected to trucut core biopsy and finally surgical excision was performed. On Histopathology this lesion was diagnosed as encapsulated apocrine papillary carcinoma with androgen receptor positivity and triple negative hormonal status. At present patient is on regular follow-up.

Conclusions

Encapsulated intracystic apocrine papillary carcinoma has a favorable prognosis with low recurrence rate and excellent long-term survival regardless of its invasive nature. Therefore, we present this rare entity to highlight the importance of radiological and histopathology findings in its diagnosis.

A Case Report on Apocrine Encapsulated Papillary Carcinoma of the Breast with Frank Invasion: A Diagnostic Quandary

Encapsulated papillary carcinoma is a special type of breast cancer defined in the fifth edition of the World Health Organization breast tumor classification guidelines. Apocrine encapsulated papillary carcinoma is extremely rare, and only 10 cases have been described previously. We encountered a case of apocrine encapsulated papillary carcinoma with frank invasion. The patient was a 77-year-old woman with a painless mass in her right breast. Core needle biopsy revealed that the tumor cells had voluminous eosinophilic cytoplasm and enlarged nuclei with prominent nucleoli. We diagnosed this lesion as carcinoma with apocrine differentiation and suggested the possibility of an encapsulated papillary carcinoma. The patient underwent a right-sided mastectomy. Gross examination of the resected specimen revealed a multilobulated tumor. Microscopically, the tumor cells, which had voluminous eosinophilic cytoplasm and enlarged nuclei with prominent nucleoli, proliferated in papillary fashion with fibrous stalks in the cystic space. Myoepithelial cells were not observed around the cystic space. Frank invasion was also observed around the encapsulated papillary carcinoma. Immunohistochemistry analysis revealed that the tumor cells were negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 and positive for androgen receptor and gross cys­tic disease fluid protein 15. Based on these findings, we diagnosed this lesion as an apocrine encapsulated papillary carcinoma with frank invasion.

Apocrine lesions of the breast

Apocrine change is recognised in benign, atypical and malignant lesions of the breast. Apocrine metaplasia, a frequent finding in the breast of women over the age of 25 years, is most commonly seen in benign cysts with a simple or papillary configuration. Apocrine change is also recognised in other benign lesions including sclerosing adenosis, now known as apocrine adenosis. Apocrine atypia usually refers to cytological atypia in which there is at least threefold variation in nuclear size but architectural atypia may also occur. The distinction between atypical apocrine hyperplasia and non-high-grade apocrine ductal carcinoma in situ may be difficult due to the relative rarity of these entities and the lack of validated diagnostic criteria. Lobular carcinoma in situ (LCIS) with apocrine change is considered to be a variant of pleomorphic LCIS. An apocrine variant of encapsulated papillary carcinoma is also recognised. Apocrine change is described in invasive carcinoma, including no special type, lobular, micropapillary and mucinous variants. The recent WHO 2019 update recognises 'carcinoma with apocrine differentiation' as a special type breast carcinoma based on the presence of apocrine morphology in at least 90% of the tumour. Tumours with apocrine morphology are usually but not always hormone receptor negative. Human epidermal growth factor receptor 2 (HER-2) status is variable. Molecular studies have identified breast tumours with apocrine features and high expression of androgen receptor mRNA including 'luminal androgen receptor tumours' and 'molecular apocrine tumours'. The term 'pure apocrine carcinoma' has been proposed to describe an invasive carcinoma with apocrine morphology that is oestrogen and progesterone receptor negative and androgen receptor positive. HER-2 status may be positive or negative. This article reviews the pathology of benign, atypical and malignant apocrine lesions of the breast, with emphasis on diagnostic criteria including an approach to evaluation of apocrine lesions on needle core biopsy, and recent advances in our understanding of invasive apocrine carcinoma.

Papillary neoplasms of the breast-reviewing the spectrum

Papillary neoplasms of the breast encompass a wide range of tumor types ranging from the benign intraductal papilloma to in situ and invasive papillary carcinomas. In this review, we considered each tumor entity listed under the Papillary Neoplasms category in the latest WHO Classification of Breast Tumors (5th edition), namely intraductal papilloma, papillary ductal carcinoma in situ, encapsulated papillary carcinoma, solid-papillary carcinoma, and invasive papillary carcinoma. We examined their pathological features, current issues pertaining to diagnosis and prognostication, as well as the latest molecular findings. We also briefly addressed adenomyoepithelioma and the newly included tall cell carcinoma with reversed polarity, highlighting areas where they overlap with papillary neoplasms.

Histological type and typing of breast carcinomas and the WHO classification changes over time

The World Health Organization’s new classification of breast tumors has just been published. This review aims to examine the morphological categorization of breast carcinomas which is still principally based on histological features and follows the traditions of histological typing. It gives a subjective and critical view on the WHO classifications and their changes over time, and describes the changes related to some of the most common or challenging breast carcinomas: in situ carcinomas, invasive breast carcinomas of no special type, lobular, cribriform, tubular, mucinous, papillary, metaplastic carcinomas and carcinomas with medullary pattern and those with apocrine differentiation are discussed in more details. Although the 5^th edition of the classification is not perfect, it has advantages which are mentioned along with problematic issues of classifications.

Mixed Invasive Apocrine Papillary/Micropapillary Carcinoma of the Breast: Another Brick in the Triple-Negative Wall

Pure invasive papillary carcinoma (IPC) is a rare subtype of breast carcinoma with good prognosis compared with classical invasive breast carcinoma (IBC) of no special type. The majority of IPC are estrogen receptor and progesterone receptor (ER/PR) positive and HER2 negative (luminal A-like). We report the case of a 72-year-old women who was referred to the Senology Clinic for a routine workup following surgery for an intraductal papilloma. The core needle biopsy (CNB) showed a lesion mainly composed of irregular papillae and micropapillae with apocrine epithelial cells of low-to-intermediate nuclear grade, without a myoepithelial cell layer within the papillae and at the periphery, as demonstrated with multiple immunostains. The diagnosis of apocrine papillary lesion of uncertain malignant potential was made. The subsequent lumpectomy showed an IBC with the same cyto-architectural features as the CNB. In addition, lymphovascular invasion and papillary/micropapillary apocrine in situ lesion were noted. Notably, the tumor was ER/PR and HER2 negative and strongly positive for androgen receptor. A final diagnosis of mixed apocrine papillary/micropapillary carcinoma with triple-negative status was made. To the best of our knowledge, this is the first report of an IBC with these features. Breast pathologists should be aware of this entity when dealing with CNB samples characterized by a complex papillary lesion with apocrine atypia that lacks a myoepithelial cell layer on multiple immunostains. These lesions should be classified at least as of uncertain malignant potential based on the cyto-architectural features prompting a surgery for removal.

Intracystic papillary carcinoma: clinical presentation, patterns of practice, and oncological outcomes

BACKGROUND

Intracystic/encapsulated papillary carcinoma remains a poorly understood disease of the breast with a little amount of reports that describe it. It shares features with DCIS and IDC and predominantly affects postmenopausal women. This study aims to evaluate the clinical presentation, treatment, and outcomes in IPC patients managed at our institution.

METHODS

We retrospectively pooled twenty-eight IPC patients' medical records at our institution. Descriptive analysis of clinicopathological characteristics, approach, and outcomes was done along with a quantitative statistical analysis.

RESULTS

Cases were divided into three groups: isolated IPC, IPC associated with DCIS, and IPC associated with Invasive Carcinoma. Treatment modalities varied according to the IPC type and its associated components. All patients presented with a palpable mass. Immunohistochemical staining revealed that all isolated IPCs were ER and PR positive and HER2 negative. Lymph node dissection proved necessary only in IPC associated invasive carcinoma. Irregular borders and lobulations, among others, were found on non-invasive core biopsies that turned out to be associated with invasion on surgical pathology. All patients were alive after a median follow-up time of 23 months when the study was over with no reports of recurrence.

CONCLUSION

IPC cases and treatment approaches at our institution appear similar to the available literature and confirm the excellent prognosis among IPC. Even more, further studies into the key features such as BMI, family history, and radiological findings are necessary for a potential algorithm that could assess for risk of finding invasion in surgical pathology and subsequently the need for axillary/sentinel lymph node biopsy.