Solitary intramammary schwannoma mimicking phylloides tumor: Cytological clues in the diagnosis

Abstract

A 30-year-old woman presented with a huge exophytic lobulated mass in the right breast, clinically and radiologically resembling phylloides tumor. Fine needle aspiration cytology smears showed clusters and singly scattered spindle cells along with structures reminiscent of verocay bodies. However, the epithelial elements were absent. A cytological diagnosis of benign mesenchymal spindle cell lesion, suggestive of schwannoma was rendered. Subsequent histopathological examination and strong S-100 positivity of tumor cells on immunohistochemistry confirmed the diagnosis.Breast is an uncommon location for benign schwannoma. The present case describes the unusual clinical picture, highlights cytological features and discusses the differential diagnoses of schwannoma from other benign spindle cells lesions of the breast on cytology smears.

Mesenchymal Tumors of the Breast: Fibroblastic/Myofibroblastic Lesions and Other Lesions

“…Most peripheral schwannomas affect the head, neck, and extremities; mammary schwannomas account for only 2.6% of schwannomas [103]. A 2011 report identified only 27 cases in worldwide literature [103] and in our literature search, we identified a further 17 cases in women [104][105][106][107][108][109][110][111][112][113][114][115][116][117] and 2 male cases [118,119]. Sporadic cases account for 90% of cases [84], whereas the rest are syndromic and associated with neurofibromatosis type 2 or familial schwannomatosis [84].…”

“…FNA results are variable depending on whether the needle goes through an Antoni A or B area (see below). CNBs are generally required to identify Verocay bodies [115]. Excisional biopsy is often needed [120].…”

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

“…A myxoid background may be seen in cases with myxoid stroma. In schwannomas with “ancient” changes, marked nuclear atypia, macrophages, and hyalinized fibrous fragments can be identified on cytology and should not be misinterpreted as malignant …”

“…The FNAC differential diagnosis of schwannoma includes phyllodes tumors, smooth muscle tumors, fibromatosis, metaplastic carcinoma, neurofibroma, and possibly myoepithelioma. Fibroepithelial lesions may be distinguished by the presence of ductal epithelial cells which are absent in most schwannomas, as these nerve sheath tumors typically grow in a pattern that is devoid of mammary epithelium . The distinction from other spindle cell lesions may be challenging as palisading patterns can be observed in some smooth muscle tumors and fibromatous tumors.…”