Histiocytoid variant of invasive lobular breast carcinoma. A case report and literature review.

INTRODUCTION: Histiocytoid breast carcinoma (HBC) is a variant of invasive lobular carcinoma. The occurrence of HBC is rare and the natural history and clinical course of HBC is still not well known due to limited numbers of reported cases. In reality, many tumors have been misdiagnosed and reported as benign lesions.

CASE PRESENTATION: A 66-year-old- postmenopausal women, who has previous personal history of right breast invasive ductal carcinoma, for which she underwent right breast wide local excision with negative sentinel lymph node biopsy and received adjuvant radiotherapy and hormonal therapy. Two years later, a new left breast suspicious lesion was detected by Imaging. Breast Ultrasound showed left breast hypo-echoic area at 12-1 o'clock with irregular spiculated lesion 3 cm away from the nipple with posterior acoustic shadowing measuring 1 × 0.7 × 0.7 cm and mild tissue distortion with thicken cortical left Axillary lymph node. Mammography of both breasts confirmed the left breast lesion at 12o'clock with necrosis and irregular margins measuring 1.1 × 1.0 cm. MRI breasts showed, left breast heterogeneously enhancing mass at 12 o'clock with no other suspicious mass in the left or right breast. Ultrasound guided left breast biopsy of the suspicious lesion seen at 12-1 o'clock which confirmed the diagnosis of invasive lobular carcinoma, histiocytoid variant She underwent wire guided left breast wide local excision with left sentinel lymph node and axillary clearance. Final histopathology showed invasive lobular carcinoma, histiocytoid variant.

CLINICAL DISCUSSION: The recognition of histiocytoid breast carcinoma is often a challenge, particularly when histiocytoid tumor cells occur in a metastatic site before the primary diagnosis of breast cancer. An awareness of histological features are needed to make the accurate diagnosis.

CONCLUSION: Findings that support the correct diagnosis include identifying tumor cells with more cytological atypia, the presence of cytoplasmic vacuoles and secretions. Moreover, coexistence with invasive lobular carcinoma and/or lobular neoplasia and the use of immunohistochemistry to confirm their epithelial nature. clinico-radiological correlation is essential, as any discordance should trigger further diagnostic determination.