Periductal Stromal Tumor of the Breast: One Institution's Review of 6 Tumors Over a 22 Year Period With Immunohistochemical Analysis

Abstract

Introduction. Periductal stromal tumor (PST) of the breast is a rare fibroepithelial neoplasm with controversial pathogenesis. Methods. A retrospective search of our Pathology database from 2000 to 2021 identified 6 PST, all evaluated according to the Armed Forces Institute of Pathology (AFIP) criteria. Immunohistochemistry for CD10, CD34, CD117, GATA3, p63, SOX10, ER, PR, HER2, smooth muscle actin (SMA), beta-catenin, and myogenin was performed as well. Results. All 6 patients were female and age ranged from 29 to 55 years (mean 40 years). Tumor size ranged from 2.9 to 5.9 cm (mean 3.0 cm). Data showed absence of leaf-like architecture (0/6), at least moderate hypercellularity (6/6), lack of a circumscribed border (5/6), coalescing nodules with intermixed adipose tissue (4/6), at least moderate stromal atypia (4/6), and an elevated mitotic activity ≥3mitotic figures/10 HPF (6/6). The stromal cells were positive for CD10 (4/4), CD34 (4/4), CD117 (3/4), and SMA (3/4), and negative for GATA3 (0/6), p63 (0/6), SOX10 (0/6), ER (0/4), PR (0/4), HER2 (0/4), nuclear beta-catenin (0/5), and myogenin (0/4). No patient had a PST recurrence or metastasis (average follow-up of 91 months). Conclusion. We confirm that PST shares morphologic and immunophenotypic similarities with phyllodes tumor (PT). However, PST can be reliably differentiated from PT using the AFIP criteria. Additionally, PST's immunoprofile of positive CD117 and CD34 stromal expression alongside the negative GATA3, p63, and SOX10 reactivity can aid the pathologist in excluding metaplastic carcinoma. All 6 of our PST behaved as benign neoplasms akin to benign PT.

Periductal Stromal Tumor of the Breast with a TERT Promoter Mutation: First Case Report with Comprehensive Molecular Analysis

“…15 In the two largest case series of periductal stromal tumors which included 13 total cases, all behaved in an indolent fashion akin to benign phyllodes tumors. 1,16 To investigate the molecular genetic landscape of a periductal stromal tumor, we performed NGS and CMA on a single case, which revealed a TERT mutation in the promoter region (−124C > T), identical to TERT mutations found in up to 65% of phyllodes tumors, along with numerous chromosomal alterations. These data could lend support to classifying periductal stromal tumors as phyllodes tumors.…”

Reassessing Breast Cancer-Associated Fibroblasts (CAFs) Interactions with Other Stromal Components and Clinico-Pathologic Parameters by Using Immunohistochemistry and Digital Image Analysis (DIA)

“…A limited number of papers assessed both αSMA_CAF and CD34_CAF interplay in breast cancer stroma [73], with most of them being related to the diagnosis of breast pathologic conditions [74][75][76] other than invasive breast cancer molecular subtypes. This may be the main reason why CD34_CAFs' role in highly aggressive BC subtypes such as HER2 and TNBC is underestimated in its relationship with other clinic-pathologic parameters and stromal vascular and immune components.…”

Survey of recurrent diagnostic challenges in breast phyllodes tumours

“…The periductal stromal tumour (PST), which features cellular and variably atypical stroma hugging ducts and lobules, without circumscription or stromal fronds, is now regarded as a subtype of PT 1,58–60 …”

“…The periductal stromal tumour (PST), which features cellular and variably atypical stroma hugging ducts and lobules, without circumscription or stromal fronds, is now regarded as a subtype of PT. 1,[58][59][60] Diagnostic issues in core biopsies may arise when a PT with morphologically heterogeneous areas (including FA-like foci) is sampled. Mitotic activity (≥2/ 10 hpf), marked stromal hypercellularity, stromal overgrowth, adipose tissue infiltration, ill-defined lesional borders, lesional heterogeneity, subepithelial condensation, stromal nuclear atypia, tissue (core) fragmentation, large lesion size, and older age group, are features reported to be predictive of a PT (as opposed to FA) diagnosis.…”