Abstract PO2-21-01: Granular Cell Tumors of the Breast: A Case Series
Authors: Kochi Shwetha , Karsten Madeline , Masanam Monika , Thorson Teagan , Derakhshandeh Roshanak , Wehner Patricia , Cruz Lucy De La , Son Jennifer 
Published: May 2024

Abstract
Objective: Granular cell tumors (GCT) of the breast are rare, Schwann-cell derived tumors that are largely benign in nature, but may present with malignant characteristics in 1-2% of cases. There are few reports highlighting the clinical presentation, cytologic differences, operative management and clinical outcomes of patients with these benign versus malignant GCTs. Here, the authors report the clinical course of 9 patients identified with either benign or malignant GCT of the breast. Methods: The medical records for a total of 9 patients treated for histologically confirmed GCT of the breast between March 2015 and May 2023 at our institution were retrospectively reviewed. Clinical data, imaging findings, immunohistochemical markers, surgical interventions, and clinical follow-up data were collected and analyzed. Results: All patients were female, with a mean age of 46 years (Range: 29-61). 5 (56%) patients presented with left-sided lesions with an average maximum dimension of 1.1 cm (SD: 0.7 cm). All 9 (100%) tumors were positive for S100, 4 (44%) were positive for CD68, and 3 (33%) were positive for Inhibin. 4 (44%) patients underwent local mass excision, 3 (33%) underwent lumpectomy, 1 (11%) underwent lumpectomy with sentinel lymph node biopsy, and 1 (11%) underwent partial mastectomy with sentinel lymph node biopsy. There were no perioperative complications nor complications noted at postoperative follow up visits. 1 patient (11%) had 2 recorded recurrences of GCT after the initial breast mass excision, with each tumor exhibiting different positive immunohistochemical markers. 1 (11%) patient had a previous history of breast cancer at time of GCT diagnosis, and 1 (11%) patient had concurrent breast malignancy with the granular cell tumor being in the lymph node of the same breast. Conclusions: Granular cell tumors of the breast are rare Schwann cell derived tumors that often present near breast scar tissue as spiculated, ill-defined masses with microcalcifications on radiologic imaging, mimicking breast malignancy, leading to overtreatment. This study found that for GCTBs that present in lymph nodes, regardless of low malignant potential seen histologically, there was a higher risk of recurrence, and may require further workup and close follow up after wide local excision. For all other granular cell tumors presenting with normal appearing lymph nodes on imaging, a local mass excision was adequate in management, with low risk of recurrence or malignant potential. Future studies should be performed analyzing long-term follow up for these patients to determine risk of recurrence over longer periods of time, and risk for breast malignancy.
Granular Cell Tumor Characteristics
Tumor characteristics including laterality, tumor location, maximum dimension in centimeters, and positive immunohistochemistry markers were shown for each patient.
Citation Format: Shwetha Kochi, Madeline Karsten, Monika Masanam, Teagan Thorson, Roshanak Derakhshandeh, Patricia Wehner, Lucy De La Cruz, Jennifer Son. Granular Cell Tumors of the Breast: A Case Series [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-21-01.