Low-grade adenosquamous carcinoma of the breast: A diagnostic and clinical challenge

Abstract

Adenosquamous carcinoma of the breast (ASBC) is a rare variant of metaplastic breast cancer with both glandular as well as squamous differentiation. Their lack of distinct imaging characteristics, sometimes subtle histological characteristics and overlapping features with other benign lesions pose a diagnostic challenge. Unlike other forms of metaplastic breast cancer, low-grade adenosquamous carcinoma (LGAC) tends to follow an indolent course with favourable prognosis. We reviewed eight cases of LGAC in our institution from June 2005 to March 2014. In six cases, LGAC was only found after excisional biopsy. In our patients, LGAC frequently co-existed with other forms of breast pathology. Two patients had incidental findings of LGAC alongside their primary malignant tumour (adenoid cystic carcinoma and invasive ductal carcinoma in one, four foci between 0.5 and 4.0 mm within a radial sclerosing lesion adjacent to a malignant phyllodes tumour in the other). A further four patients had LGAC within a complex sclerosing lesion. One patient had a focus of LGAC within a fibroadenoma. One had a focus of LGAC within a benign phyllodes tumour. None of the patients had evidence of nodal involvement. A high degree of suspicion is recommended as such lesions tend to be incidental histological findings within benign tumours or within complex sclerosing lesions. Although the risk of nodal and distant metastasis is low, the potential for local recurrence necessitates aggressive local excision with margin clearance. The role of axillary dissection has yet to be defined and routine sentinel node biopsy and axillary clearance may not be necessary in view of rarity of nodal metastasis in literature. Benefit from adjuvant radiotherapy or chemotherapy is not clearly defined. All eight patients in our study have shown no evidence of recurrence after definitive surgery but longer periods of surveillance is required.

Bilateral synchronous low-grade adenosquamous carcinoma of the breast: A Case report with review of the current literature

“…Clinically, LGASC occur in patients of any age (19-88) and commonly present as a palpable mass rather than an incidental finding on mammography [12,17,19] . Though LGASC is locally invasive, and despite a ‘triple-negative’ profile, metastases are rare and patients have an overall good prognosis, different from other metaplastic carcinomas of the breast [1,3,6,7,17,18] .…”

“…A total of 18 manuscripts (1987 to present) describing 109 cases of LGASC are summarized in Table 1 [1–18] . Patients’ ages range from 19 to 88, with two cases of bilateral LGASC being reported.…”

“…Low-grade adenosquamous carcinoma (LGASC) of the breast is exceedingly uncommon, belonging to the family of ‘metaplastic breast cancers’ which represent <1% of all breast carcinomas [1] . In contrast to the highly aggressive, triple-negative, chemo-resistant features of most metaplastic breast cancers, LGASC portends an indolent course, with a low metastatic potential and thus an improved prognosis [2,3] . Reports of LGASC in the published literature are limited.…”

Metaplastic Breast Carcinoma: Update on Histopathology and Molecular Alterations

“…First described in 1987, low-grade adenosquamous carcinoma of the breast is a rare variant of metaplastic carcinoma defined by having both glandular and squamous differentiation embedded in a bland spindle cell background. [3][4][5] These tumors have low nuclear grade and, although areas may resemble tubular carcinoma, the neoplastic glands of adenosquamous carcinoma have smooth rounded contours as opposed to the characteristic angulated glands of tubular carcinoma. The amount of squamous differentiation can vary from minimal to extensive.…”

Adenosquamous Carcinoma of the Breast: A Population-Based Study Using the SEER Database

“…Though several case reports and case series were published over the years [4,5], ASC remains poorly de ned by immunohistochemistry and its genetic pro le is still unclear [6]. From these limited studies, it appears that ASC differs from its counterparts in this heterogeneous category by its relative clinical indolence, also re ects histologically in its cytomorphology [7].…”