breast localization of granular cell tumor (GCT)

Clinical History

We present a case of a 59-year-old woman, who presented at our department after noticing an elastic hard mass in the upper quadrant of the right breast.

Imaging Findings

Mammograms showed a dense mass with spiculated margins in the right axilla (Fig. 1). Ultrasound confirmed the presence of a hypoechoic mass with irregular borders and posterior acoustic shadowing.
Then a CT examination was performed before and after administration of contrast media, which showed the presence of an enhancing mass in the right axilla without other findings (Fig. 2-3). Core biopsy was not performed due to the location of the lesion.
She then underwent an excisional biopsy, which showed polygonal cells carrying granular eosinophilic cytoplasm. The nuclei were round to oval and no mitotic figures were observed. The tumour cells were immunoreactive to S-100 proteine, but they were negative for desmin and oestrogen receptor. Thus, a histological diagnosis of benign GTC was established.

Discussion

Background
Granular Cell Tumours (GCTs) are uncommon, usually benign neoplasms that can originate anywhere in the body, but are most frequently found in the head and neck area, particularly in the oral cavity. They rarely occur in the breast, this location accounting only for 4%-6% of all cases [1-2]. GCT was first described by Abrikosoff in 1926 as a “myoblastic myoma” [3]. Subsequently, immunohistochemical and ultra-structural features have proposed a perineural or Schwann cell origin. The neoplastic cells typically express S-100 and CD68 (KP-1) proteins, the latter as result of cytoplasmic lysosome content. However, the exact histogenesis of this tumour is still controversial. Distinction between benign and malignant GCTs is difficult because of their histological similarity and lack of reliable criteria that can predict tumour behaviour [4].

Clinical Perspective
The clinical appearance of GCTs when occurring in the breast can mimic carcinoma because of their fibrous consistency and their hardness, thus presenting as a palpable mass.

Imaging Perspective
On mammography, these tumours can present as an ill-defined or spiculated lesions, similar to primary carcinoma. Ultrasound can also show a lesion that is very similar to a cancer, as it can be irregular, hypoechoic, and can present the posterior acoustic shadow [5].
Diagnosis is possible by means of biopsy and histological examination, since diagnostic imaging features, as well as clinical presentation are almost indistinguishable from breast carcinoma. However, in some experiences it is also described that aspiration cytology (FNAB) can be useful in differential diagnosis between GCT and breast carcinoma [2-5].

Outcome
Therapy is represented by surgery, as these tumours are mostly benign, but they need to be completely resected to avoid tumour growth.
Moreover, surgical excision should be as wide as possible in order to prevent tumour recurrence that is quite common despite of the benign nature.

Take Home Message
GCT breast localisations are very rare, but they can mimic breast carcinoma at imaging. Diagnosis is possible only performing biopsy although FNAB can be also useful in differential diagnosis between GTC and breast carcinoma. Surgery is the only therapy for this kind of tumour.

Differential Diagnosis List

Final Diagnosis

Granular Cell Tumour (Abrikosoff's tumour)

URL:	https://www.eurorad.org/case/9270
DOI:	10.1594/EURORAD/CASE.9270
ISSN:	1563-4086