Malignant phyllodes tumour of the breast mimicking endometriosis

Breast phyllodes tumour with epithelioid feature predisposes to malignant transformation

AIMS

Phyllodes tumours (PTs) are relatively common fibroepithelial tumours comprising epithelial and stromal component. Usually, PTs show a spindle cell morphology with a fibroblast phenotype, while some tumour cells exhibit epithelioid morphological features and sarcomatoid transformation. However, the molecular characteristics of this morphology subset remain unclear. This study aimed to summarise the clinicopathological, morphological and molecular characteristics of seven cases of PT with epithelioid features.

METHODS

Morphological and clinicopathological characteristics were observed and retrieved. Immunohistochemistry, immunofluorescence and electron microscope were performed on seven cases of epithelioid PT to explore immunophenotypic and ultrastructural characteristics. Transcriptomic and proteomic analyses were conducted to compare differentially expressed genes and proteins between epithelioid PT and classical PT.

RESULTS

Patients with epithelioid PT exhibit a high recurrence rate (42.8%). Morphologically, in addition to having epithelioid cytological features, neoplastic stromal cells exhibit moderate to marked atypia and often exhibit sarcomatoid transformation, similar to the characteristics of borderline PT. Transcriptomic and proteomic analyses demonstrated that epithelioid PTs are distinct from classical PTs in gene expression and protein abundance levels. Immunohistochemical analysis showed that among all differentially expressed proteins, epithelioid PT showed abnormal p16/retinoblastoma expression patterns, similar to those of malignant PT.

CONCLUSIONS

Epithelioid PT has unique morphological characteristics, biological behaviour and protein expression profile, which meets the diagnostic criteria of borderline PT and is prone to sarcomatoid transformation. It may be a special morphological subgroup of borderline PT and has partial characteristics of malignant PT, which should be taken seriously in pathological diagnosis and clinical management.

Iatrogenic Endometriosis of the Breast Mimicking Fat Necrosis: A Case Report

A female patient with a history of ductal carcinoma in situ in the left breast, status-post bilateral mastectomy with deep inferior epigastric perforator artery flap reconstructive surgery, presented with a right breast asymmetry concerning for fat necrosis. Histological analysis revealed the presence of benign glands and associated stroma within fibroadipose tissue, confirmed as endometriosis by immunohistochemical analysis. Further investigation revealed that the patient had a previous diagnosis of endometriosis associated with a cesarean section scar that likely seeded the ectopic endometrial glands into a tertiary site by utilizing abdominal tissue that may have harbored endometriosis.

Versican core protein aids in the diagnosis and grading of breast phyllodes tumor

Phyllodes tumors (PTs) are biphasic fibroepithelial lesions that occur in the breast. Diagnosing and grading PTs remains a challenge in a small proportion of cases, due to the lack of reliable specific biomarkers. We screened a potential marker versican core protein (VCAN) through microproteomics analysis, validated its role for the grading of PTs by immunohistochemistry, and analyzed the correlation between VCAN expression and clinicopathological characteristics. Cytoplasmic immunoreactivity for VCAN was identified in all benign PT samples, among which 40 (93.0 %) showed VCAN-positive staining in ≥50 % of tumor cells. Eight (21.6 %) borderline PT samples showed VCAN-positive staining in ≥50 % of the cells with weak to moderate staining intensity, whereas 29 samples (78.4 %) showed VCAN-positive staining in <50 % of the cells. In malignant PTs, 16 (84.2 %) and three (15.8 %) samples showed VCAN-positive staining in <5 % and 5-25 % of stromal cells, respectively. Fibroadenomas showed a similar expression pattern to benign PTs. Fisher's exact test showed that the percentages of positive cells (P < .001) and staining intensities (P < .001) of tumor cells were significantly different between the five groups. VCAN positivity was associated with tumor categories (P < .0001) and CD34 expression (P < .0001). The expression of VCAN gradually decreases as the tumor categories increases, following recurrence. To the best of our knowledge, our results are the first in the literature to reveal that VCAN is useful for diagnosing and grading PTs. The expression level of VCAN appeared to be negatively associated with PT categories, suggesting that dysregulation of VCAN may be involved in the tumor progression of PTs.

Morphological features of 52 cases of breast phyllodes tumours with local recurrence

Typical phyllodes tumours (PTs) of the breast are fibroepithelial neoplasms characterised histologically by stromal hypercellularity and leaf-like structures. However, morphological changes may be atypical in some cases, increasing the difficulty of diagnosis and the likelihood of misdiagnosis. To provide more morphological clues for pathological diagnosis of PTs, we retrospectively analysed 52 PT cases with typical morphological features after recurrence, and summarized the clinicopathological characteristics of the paired primary tumours. We found five special histological features in the primary tumours distinct from classic PTs, namely (1) PTs with epithelioid feature (three cases); (2) PTs with gland-rich feature (eight cases); (3) PTs with fibroadenoma-like feature (20 cases); (4) PTs with myxoid fibroadenoma-like feature (five cases); and (5) PTs with pseudohemangiomatoid stromal hyperplasia–like feature (four cases). All the features can exist independently, and a few cases displayed more than two distinctive features at the same time. In this cohort of recurrent PTs, all the primary tumours were absent of recognisable stromal hypercellularity and leaf-like structures that are the critical diagnostic criteria of PTs; however, they showed some other non-classic characteristics which may provide significant clues for the diagnosis of PTs. Particularly, tumours with epithelioid feature displayed high grade at earlier stages, tumours with fibroadenoma-like feature were most likely to be confused with classical fibroadenomas, and tumours with myxoid feature were prone to be neglected because of their hypocellularity.