Granular cell tumor of the breast

Case contributed by Dr Mark Holland

Presentation

2nd round breast screen patient recalled due to 8mm, spiculated mass on the edge of the film. At breast assessment clinic there was no palpable breast mass, no mass on further mammographic views and no breast mass at ultrasound. MR confirmed the true position of the mass, just inferior to the axilla and an ultrasound biopsy was performed.

Patient Data

Age: 55 years
Gender: Female

Breast assessment mammogram

Mammography

Spiculated mass overlying the left pectoral muscle that is better seen on an extended lateral film.

BIRADS R4 (Tabar / Nottingham 4A) appearance at mammography, ultrasound and MR.

Biopsy result is a benign granular cell tumor that expresses S100 (P2).

Tumor was surgically resected and the patient was reassured.

Ultrasound

Vascular irregular mass had ultrasound-guided 14G needle core biopsy performed.

Breast assessment MRI was performed to further characterize the mass.

Pathology

Macroscopy

An irregular firm stellate lesion with white cut surface measuring 20 x 15 x18 mm.

Microscopy

Solid nests of cells, cords and sheets of cells with abundant eosinophilic granular cytoplasm, prominent nucleoli and moderate cellular atypia.

Polygonal, spindle-like cells resting in a hyaline, fibrous stroma.

The cells have distinct borders, small centrally to eccentrically placed nuclei, inconspicuous nucleoli and abundant eosinophilic cytoplasm. B

The cytoplasm contains numerous fine granules as well as scattered larger eosinophilic granules.

There is no evidence of nuclear pleomorphism, multinucleated cells or mitosis.

Stains and Immunohistochemistry

  • DPAS positive
  • Nuclear and cytoplasmic positivity for S100.
  • Cytoplasmic staining for CD68, due to their lysosomal activity.
  • Negative for Cytokeratins, HMB45 and Melan-A

Case Discussion

Granular cell tumors were originally described by Abrikossoff in 1926 and are usually found in the mouth or skin but 6% occur in the breast. Up to 10% are multiple. Incidence < 1 in a 1000 breast masses. Occurs from 20 – 80 but around 40 years of age most common with slight preponderance in premenopausal black women.

Usually less than 30mm in size, and are most frequently found in the upper inner quadrant (supraclavicular nerve territory) followed by the axillary tail.  They are a neuroendocrine tumor of perineural or Schwann cell origin that typically express S100 and CD68 (KP-1).

At mammography -  range from a round well-circumscribed mass, to an indistinct or spiculated lesion. Microcalcifications are not usually a feature.

At ultrasound, present as solid, poorly marginated lesions with marked posterior shadowing or as more benign-appearing well-circumscribed solid masses. Lesion often have a reflective halo or are partially hyper-reflective which is due its infiltrative growth pattern.

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