Abstract P3-08-03: Dissecting the heterogeneity of metaplastic breast cancer: A morphological, immunohistochemical and genomic analysis of a large cohort

Although rare, Metaplastic Breast Carcinomas (MBC) account for significant global breast cancer mortality. This subgroup is extremely heterogeneous and by definition exhibits metaplastic change to squamous and/or mesenchymal elements, including but not limited to spindle, squamous, chondroid, osseous and rhabdomyoid elements. The WHO working group recognizes that the current classification is inadequate and in the interim, has suggested a purely descriptive classification. The mixed epithelial-mesenchymal morphology has led to speculation that MBC represent 'stem cell tumours'; in support of this, MBC have been shown to have a CD44+/CD24-/low phenotype. Clinically, patients present with tumours that are larger (higher stage), have increased likelihood of distant metastases at presentation and overall, have a reduced 5-year survival rate compared to Invasive Carcinoma-NST. Hence, this is a unique subtype with poor outcome but without a robust classification or understanding of the biology to aid clinical management. We present a detailed morphological, immunohistochemical and genomic analysis of a large series of MBC (n=347), as amassed through the Asia-Pacific MBC consortium. We consider our morphological dissection using the WHO subtyping guidelines and show that an increasing number of phenotypes in a mixed MBC (classified as WHO_1) significantly associates with a poor prognosis. Immunohistochemical analysis showed that a pure spindle (WHO_5) is significantly less likely to express vimentin, CK5/6, CK14, and CK19 than a mixed WHO_1 with spindle features. Similarly, a WHO_1 with chondroid features is less likely to express EGFR than WHO_1 with chondroid features and rhabdoid or osseous differentiation. Across the cohort, positivity for the AE1/3 antibody and a lack of EGFR expression both significantly associate with a better outcome. We report no significant association between patient age at diagnosis and breast cancer specific survival, nor between age and specific WHO MBC subtypes. We report a significant association between WHO_1 types and increasing tumour grade, and also between tumour size and grade, with tumour size being a highly significant prognostic indicator in this cohort. Our exome sequencing confirms a significant enrichment for TP53 and PTEN mutations in MBC, and intriguingly for concurrent mutations of TP53, PTEN and PIK3CA. A novel enrichment for NF1 mutations is also presented. In summary, we provide a thorough assessment of a large cohort of MBC, including morphology, survival, IHC and exome sequencing, and present our analysis contextualized by the WHO guidelines, extending the existing knowledge base of this rare tumour type.

Citation Format: McCart Reed AE, Kalaw E, Nones K, Bettington M, Lim M, Bennett J, Johnstone K, Kutasovic JR, Kazakoff S, Xu QC, Saunus JM, Reid LE, Black D, Niland C, Ferguson K, Gresshoff I, Raghavendra A, Liu JC, Kalinowski L, Reid AS, Davidson M, Pearson JV, Yamaguchi R, Harris G, Tse G, Papadimos D, Pathmanathan R, Pathmanathan N, Tan PH, Fox S, O'Toole S, Waddell N, Simpson PT, Lakhani SR. Dissecting the heterogeneity of metaplastic breast cancer: A morphological, immunohistochemical and genomic analysis of a large cohort [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-08-03.

Rapid on-site evaluation of fine needle aspiration specimens by cytology scientists: a review of 3032 specimens

OBJECTIVES

To determine: (1) the accuracy of cytology scientists at assessing specimen adequacy by rapid on-site evaluation (ROSE) at fine needle aspiration (FNA) cytology collections; and (2) whether thyroid FNA with ROSE has lower inadequacy rates than non-attended FNAs.

METHODS

The ROSE of adequacy for 3032 specimens from 17 anatomical sites collected over a 20-month period was compared with the final report assessment of adequacy. ROSE was performed by 19 cytology scientists. The report profile for 1545 thyroid nodules with ROSE was compared with that for 1536 consecutive non-ROSE thyroid FNAs reported by the same cytopathologists during the study period.

RESULTS

ROSE was adequate in 75% (2276/3032), inadequate in 12% (366/3032) and in 13% (390/3032) no opinion was rendered. Of the 2276 cases assessed as adequate by ROSE, 2268 (99.6%) were finally reported as adequate for assessment; eight specimens had adequacy downgraded on the final report. Fifty eight per cent of cases with a ROSE assessment of inadequate were reported as adequate (212/366), whereas 93% (363/390) with no opinion rendered were reported as adequate. The overall final report adequacy rate for the 3032 specimens was 94% (2843/3032). Confirmation of a ROSE of adequacy at reporting was uniformly high amongst the 19 scientists, ranging from 98% to 100%. The inadequacy rate for thyroid FNAs with ROSE (6%) was significantly (P < 0.0001) lower than for non-ROSE thyroid FNAs (17%). A significantly (P = 0.02) higher proportion of adequate ROSE thyroid specimens was reported with abnormalities, compared with non-ROSE thyroid collections.

CONCLUSIONS

Cytology scientists are highly accurate at determining specimen adequacy at ROSE for a wide range of body sites. ROSE of thyroid FNAs can significantly reduce inadequate reports.

Diagnostic value of p53 immunohistochemistry in Barrett's esophagus: an endoscopic study

The aim of this study was to establish the diagnostic utility of p53 immunohistochemistry in Barrett's esophagus. Three pathologists reviewed endoscopic biopsy specimens and one surgical specimen derived from 102 subjects in a prospective follow-up series. Dysplasia was graded as negative, indefinite, low grade and high grade. p53 staining was assessed as negative, weak or patchy and strong. Kappa coefficients for interobserver agreement for the three combinations of observer pairs were moderate to substantial (0.48, 0.55 and 0.68) for dysplasia and substantial to near perfect (0.77, 0.82 and 0.89) for p53 immunostaining. In the consensus grading achieved for dysplasia, strong p53 staining was recorded in 0/79 samples that were negative or indefinite for dysplasia, 5/15 (33%) examples of low grade dysplasia and 7/8 (87%) examples of high grade dysplasia. Non-dysplastic p53 positive glands were seen in specimens from two subjects harbouring dysplasia or cancer elsewhere. Two p53 positive specimens were, upon review and discussion, re-assigned from low- to high-grade dysplasia. It is concluded that p53 immunohistochemistry facilitates the interpretation of Barrett's epithelium but need only be employed to confirm a suspected diagnosis of dysplasia and assist with the distinction between low- and high-grade dysplasia.

A technique for the culture of Barrett's oesophageal cells

Establishment of cells in tissue culture from Barrett's columnar epithelium has been difficult. The aim of this study was to develop a successful tissue culture method employing a serum-free medium for cultivation of Barrett's epithelial cells. Fragments of Barrett's mucosal tissue were explanted in a 3:1 mixture of Dulbecco's modification of Eagle's medium and Ham's F12, to initiate the outgrowth of epithelial cells. Subsequently, a commercial serum-free medium (formulated for the growth of keratinocytes) was used for the propagation of Barrett's oesophagus cells without fibroblast growth. Cells established in culture retained their epithelial morphology, stained positive for cytokeratin, and contained Alcian blue (pH 2.5) and periodic acid-Schiff reagent-positive/diastase-resistant vacuoles, confirming their origin from Barrett's epithelium. Electron microscopy showed tonofilaments, microvilli and desmosomes. Coating the surface of culture vessels was not required and four cell strains could be passaged up to 20 times with no fibroblast growth, in the keratinocyte serum-free medium.

Endoscopic sclerotherapy: lessons from a necropsy study

A retrospective necropsy survey of 13 patients who had received endoscopic injection sclerotherapy was carried out to study tissue changes induced and to determine the causes of death. These results were compared with autopsy findings in nine patients with portal hypertension, comparable for age, sex, and nature and severity of underlying liver disease, who had not received sclerotherapy. Although all treated patients had variceal thrombosis with an associated vasculitis, residual varices were usually present, probably reflecting the brief duration of treatment (median, 12 days). The major complications of sclerotherapy resulted from necrosis, with resultant mucosal ulceration and abscess formation. These features were not present in the control group. Complications contributing to death were hemorrhage in three patients, and in one sepsis with deep necrosis and periesophageal abscess formation.