Fine needle aspiration cytology of nodular fasciitis presenting as a mass in the male breast: report of an unusual case

Nodular fasciitis of the breast: clinicopathologic and molecular characterization with identification of novel USP6 fusion partners

Nodular fasciitis is a benign, self-limited, pseudosarcomatous neoplasm that can mimic malignancy due to its rapid growth, cellularity, and mitotic activity. Involvement of the breast is rare and diagnosis on biopsy can be challenging. In this largest series to date, we examined the clinicopathologic and molecular characteristics of 12 cases of nodular fasciitis involving the breast/axilla. All patients were female, with a median age of 32 years (range 15-61). The lesions were 0.4 to 5.8 cm in size (median 0.8). All cases presented as palpable masses, and two patients had overlying skin retraction. Microscopically, lesions were relatively well-circumscribed nodular masses of bland myofibroblastic spindle cells within a variably myxoid stroma. Infiltrative growth into adipose tissue or breast epithelium was frequent. Mitotic figures were present in all cases, ranging from 1 to 12 per 10 high-power fields (median 3). Immunohistochemically, all cases expressed smooth muscle actin and were negative for pan-cytokeratin, p63, desmin, CD34, and nuclear beta-catenin. Targeted RNA sequencing performed on 11 cases identified USP6 gene fusions in eight; one additional case was positive by break-apart fluorescence in situ hybridization. The common MYH9-USP6 rearrangement was detected in four cases; another case had a rare alternative fusion with CTNNB1. Three cases harbored novel USP6 gene fusions involving NACA, SLFN11, or LDHA. All fusions juxtaposed the promoter region of the 5' partner gene with the full-length coding sequence of USP6. Outcome data were available for eight patients; none developed recurrence or metastasis. Five patients elected for observation without immediate excision, and self-resolution of the lesions was reported in three cases. Albeit uncommon, nodular fasciitis should be considered in the differential diagnosis of breast spindle cell lesions. A broad immunohistochemical panel to exclude histologic mimics, including metaplastic carcinoma, is important. Confirmatory detection of USP6 rearrangements can aid in classification, with potential therapeutic implications.

Nodular Fasciitis - Fine Needle Aspiration Cytology Diagnosis and Its Pitfalls, with Review of Literature

Background and Objective

Nodular fasciitis (NF) is a self-limiting, transient neo- plasm composed of fibroblasts and myofibroblasts. Since it regresses spontaneously, diagnosis by fine needle aspiration (FNA) cytology plays a major role in its management.

Methods

We present a series of 8 cases with either FNA or biopsy diagnosis ofNF, and study the major cytological features with a review of literature on diagnostic criteria and its pitfalls.

Results and Conclusion

The 8 cases occurred in patients between the age of 14 to 72 years, with equal sex distribution. FNA diagnosis concurred in 4 cases. Causes of wrong diagnosis included lack of clinical information and paucicellular smear. FNA cytology is an important tool in the diagnosis of nodular fasciitis, in appropriate clinico-radiologicalsetting.

Mammary mesenchymal and fibroepithelial lesions: An illustrated cytomorphologic update with differential diagnoses

The Uniform Approach to Breast Fine Needle Aspiration Biopsy was put forward by a learned group of breast physicians in 1997. This landmark manuscript focused predominantly on diagnosis and reporting of mammary epithelial lesions. Today, most American practitioners turn initially to core biopsy rather than aspiration biopsy for the first line diagnosis of solid breast lesions; however, recent efforts from the International Academy of Cytology have produced a system called the Standardized Reporting of Breast Fine Needle Aspiration Biopsy Cytology (colloquially labeled in 2017 as the "Yokohama System"), suggesting a new interest in breast fine needle aspiration (FNA), especially in resource limited settings or clinical practice settings with experienced breast cytopathologists. Fibroepithelial lesions of the breast comprise a heterogeneous group of biphasic tumors with epithelial and stromal elements. Mesenchymal lesions of the breast include a variety of neoplasms of fibroblastic, myofibroblastic, endothelial, neural, adipocytic, muscular, and osteo-cartilaginous derivations. The cytology of mesenchymal breast lesions is infrequently described in the literature and is mainly limited to case reports and small series. This illustrated review highlights the cytologic features of fibroepithelial and mesenchymal mammary proliferations and discusses differential diagnoses and histomorphologic correlates.

Spindle Cell Lesions of the Breast on Fine-Needle Aspiration Biopsy: A Miscellany of Masses

A variety of primary breast and metastatic lesions to the breast can present with spindle cell cytomorphology. These lesions may range from benign reactive or inflammatory lesions to high-grade malignancies. Spindle cell lesions of the breast are not often seen on fine-needle aspiration biopsy (FNAB) but need to be correctly managed when they are encountered. While mesenchymal lesions of the breast have a spindle morphology, lesions derived from the epithelium and myoepithelium can be spindled as well. By assessing if the lesion comprises spindle cells only or if other components such as epithelial cells are apparent and then determining whether the spindle cells appear bland or pleomorphic, together with close clinicoradiologic correlation and prudent use of ancillary tests, a variety of lesions can be diagnosed on FNAB. However, core needle biopsy or excision biopsy may be required in some patients. The cytomorphology, ancillary studies, and clinicoradiologic findings of a range of spindle cell lesions of the breast are further discussed.

Breast Nodular Fasciitis: A Comprehensive Review

BACKGROUND

This article describes the demographic, clinical, pathological and prognostic features of breast nodular fasciitis through a comprehensive review of the cases reported in modern literature.

MATERIAL AND METHODS

English-language articles published from January 1970 to October 2015 and related to breast nodular fasciitis were non-systematically retrieved using the PubMed database. Titles, abstracts and references were evaluated in order to include the most relevant studies. The demographic characteristics of the patients and the signs and symptoms of the disease were reviewed, as well as the results of the radiological and diagnostic procedures employed and of the treatments adopted.

RESULTS

26 papers reporting on 28 cases were enrolled; however, manuscripts published before 1990 were excluded because of old methodologies, technologies and clinical approaches. Thus, 22 cases included in 20 papers were analyzed in detail.

CONCLUSION

The rarity and the unspecific clinical and radiological characteristics of breast nodular fasciitis make the differential diagnosis and management challenging. Knowledge of the clinical, pathological and prognostic aspects of this condition is crucial for breast care specialists in order to improve their diagnostic and therapeutic interventions.

Nodular Fasciitis of the Breast

Nodular fasciitis of the breast is a rare benign pathology of soft tissue that is a consequence of fibroblastic hyperplasia within breast. It can mimic breast cancer clinically, radiologically, and histopathologically.

A-43 year-old female with a painless mass within upper-lateral quadrant of her left breast complained of rapid and progressive growth during previous few days. No evidence of nipple discharge or sensation of pain was expressed. The mass was tender to palpation, but the size was too tiny to detect. The definitive diagnosis was established with sonography, which detected a hypoechogenic lesion, 10 mm in diameter. The excisional biopsy delivered a tissue composed of fusiform fibroblastic cells with bright ellipsoid-like nuclei and elevated nucleolus. Mitotic formations were also obvious. Low cellular and high cellular zones with hyaline fibrosis and erythrocyte accumulation existed, as well as a light lymphocytic infiltration. All of these features, in addition to adipocytic accumulation within the margins of this lesion, suggested a definitive diagnosis of Nodular fasciitis. The diagnosis of nodular fasciitis is difficult and often is indiscriminable from breast cancer, so paying close attention to this matter is critical.

A spontaneously resolving breast lesion: imaging and cytological findings of nodular fasciitis of the breast with FISH showing USP6 gene rearrangement

We report a case of nodular fasciitis of the breast in a 48-year-old woman who presented with a tender rapidly growing right breast lump. Ultrasound guided fine needle aspiration (FNA) of the solid mass was performed. Cytology was reported as atypical spindle cell neoplasm and the patient was referred to a breast surgeon at a tertiary institution for a definitive diagnosis and further management. Follow-up ultrasound showed partial regression and MRI, mammogram after 2-3 weeks confirmed spontaneous and total resolution of the lesion. Nodular fasciitis of the breast is rarely diagnosed on cytology alone and a histological diagnosis is usually required for a definitive diagnosis. However, in this case, the lesion spontaneously resolved prior to core biopsy or diagnostic open biopsy. The cytological features in conjunction with immunohistochemistry and the clinical history strongly suggest nodular fasciitis, which is further supported by a USP6 FISH positive result.

Nodular fasciitis of the breast mimicking breast cancer

Nodular fasciitis is a benign proliferative lesion that is usually found in the soft tissue of the upper extremity and trunk in young to middle-aged persons. It has rarely been described in the breast. A 35-year-old woman had noticed a mass in her left breast. It was elastic-hard, 13 mm in size, and located mainly in the upper inner quadrant of the left breast. Mammography did not detect the mass. Ultrasonography revealed a hypoechoic lesion with an irregular margin. Neither fine-needle aspiration cytology nor core needle biopsy established a definitive diagnosis. Excisional biopsy was therefore performed. Histologically, the excised tumor tissue results were consistent with a diagnosis of nodular fasciitis of the breast. We report a case of nodular fasciitis of the breast, a rare histological type of breast tumor.