Fibromatosis-like metaplastic carcinoma: a case report and review of the literature

Abstract

Background:We report an unusual case of low-grade fibromatosis-like metaplastic carcinoma (LG-FLMC) of the breast. This exceedingly rare epithelial breast malignancy has been reported only 68 times in the past 20 years, and is classified as a subtype of metaplastic breast carcinoma (MBC). It is a locally aggressive tumor with a low potential for lymph node and distant metastases, but with a tendency to recur after excision. Here we describe a less common presentation of LG-FLMC, provide its molecular characterization, discuss the major differential diagnosis and bring a short review of the literature. Case presentation: A 65-year-old woman presented with a self-palpated breast lump that had discordant radiopathological features. While imaging results were compatible with an infiltrative malignancy, on core needle biopsy (CNB) a sharply delineated lesion composed by a bland-looking population of spindle cells was observed; excision was recommended for final diagnosis. Histology of the resection specimen showed small areas of epithelial differentiation and foci of peripheral invasion. Immunohistochemical analysis revealed a co-immunoreactivity for epithelial and myoepithelial markers in the spindle cell component. Mutation analysis with a capture-based next generation sequencing method revealed pathogenic mutations in GNAS, TERT-promotor and PIK3R1 genes. A diagnosis of LG-FLMC was rendered. Conclusion: This case highlights the importance of a broad differential diagnosis, exhaustive sampling and the use of a broad immunohistochemical panel whenever dealing with a low-grade spindle cell lesion in the breast, and provides further insights into the molecular background of LG-FLMC.

Spindle cell lesions of the breast: a diagnostic approach

“…Although fibromatosis-like MBC is associated with an excellent prognosis as compared with other MBCs, [16,17] local recurrence may occur and occasional metastases have been reported [18]. In the study by Gobbi et al [16], 8 of 18 patients with fibromatosis-like MBC, with available clinical follow-up, developed local recurrence.…”

“…Currently, these tumours are managed in accordance with protocols for other low-grade conventional type IBCs and systemic chemotherapy is not recommended for pure early-stage tumours. These tumours have a low potential for lymph node metastasis [18] but sentinel lymph node sampling is required for staging.…”

Triple-Negative Breast Cancer Histological Subtypes with a Favourable Prognosis

“…Fibromatosis-like metaplastic carcinoma (FLMC) represents a rare low-grade subtype of metaplastic breast carcinoma (MBC). With a total of 70 cases reported in the peer-reviewed English language literature ( Supplementary Table S3 ) [ 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ], FLMC is likely to account for significantly less than 1% of all MBCs. Due to its bland morphology, FLMC is diagnostically challenging and is likely to account for a higher relative percentage of tumours in referral centres, diagnosed at the time of primary presentation or on review following a recurrence of an incompletely excised FLMC originally (mis)diagnosed as a benign entity.…”

“…Since the first detailed description of the histological criteria for the diagnosis of FLMC by Gobbi et al in 1999 (adopted by the current WHO classification), a total of 70 cases have been published in the English-language literature with follow-up data available for 41. Overall, FLMC shows clinically indolent behaviour with a high tendency for local recurrence (14/41 cases), but with a low potential for regional lymph node (3/41 cases) or distant metastases (5/41 cases) ( Supplementary Table S3 ) [ 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ].…”

“…Regarding local therapy, wide excision appears to prevent local recurrence [ 75 , 76 , 80 ]. The available data do not support the benefit of adjuvant radiotherapy or chemotherapy in reducing the risk of local recurrence or metastasis ( Supplementary Table S3 ) [ 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 ]. However, some authors, including the present authors, advocate the use of adjuvant radiotherapy for more bulky lesions [ 90 ].…”