Gross Pathology:
- A single 2.8 cm size homogenous yellowish-tan colored solid soft to firm mass with an irregular border.
Granular cell tumor of the breast
Histopathology:
– Solid alveolar arrangement of the large cells with abundant granular eosinophilic cytoplasm and round bland nuclei. Occasional cells show small distinct nucleoli. Cell borders are not well-appreciated in the above case probably due to poor fixation and microtomy. Focal mild atypia is seen.
– Variable size nests and clusters of tumor cells infiltrate the breast tissue. Single-cell pattern of invasion is not seen.
– Mitoses, necrosis, abnormal chromatin pattern, prominent nucleoli, and spindled morphology (features suggestive of malignancy) are not seen.
Practical points of Pathoclinics:
- Granular cell tumor of the breast is an uncommon tumor, thought to arise from schwann cells. Rarely, it can also occur in axillary breast tissue.
- Clinically and radiologically, it can mimic breast carcinoma.
- In the present case, the gross image shows a single 2.8 cm size yellowish-tan colored soft to firm mass with an irregular border, mimicking carcinoma.
- Microscopically, granular cell tumors are uncapsulated poorly defined infiltrative tumor. Tumor cells are arranged in solid sheets, nests, and alveolar patterns. Single cells infiltration is not a common finding. Tumor cells are large with abundant granular cytoplasm and small round to ovoid nuclei, without prominent nucleoli or hyperchromasia. Granular cell tumors are positive for S100, calretinin, CD68 and β-catenin, while negative for CK, muscle markers, ER and PR.
- A limited tissue sample (needle biopsy) containing only large cells with granular quality of cytoplasm require immunohistochemistry, to rule out benign inflammatory/histiocytic cell rich lesion (CD68 positive but S100 negative) due to cyst rupture or fat necrosis and breast carcinoma with apocrine features (CK positive, can be positive for S100, ER and PR, and presence of cytologic atypia and in situ breast carcinoma). Alveolar soft part sarcoma is another morphologically very close to the granular cell tumor, as both are sharing an alveolar pattern, composed of large cells on low power view, but the cells are in a dyscohesive manner in alveolar soft part sarcoma and not in a solid pattern like granular cell tumor. It is positive for TFE3 (nuclear positive), along with muscle markers, and characterized by ASPL-TFE3 fusion. Alveolar soft part sarcoma also has PAS-positive intracytoplasmic crystalline structures.
- Very rarely granular cell tumors may co-incidentally be found along with in situ or invasive breast carcinoma.
- Granular cell tumor is a benign tumor, that needs complete local excision. Incomplete excision may lead to recurrence. Malignant granular cell tumors are very rare.
