The cytologic finding of proliferating trichilemmal tumor is not well documented and have difficulties in the cytological analysis of the fine needle aspirates. This rare dermatopathologic entity may be encountered during aspiration biopsy of subcutaneous masses, and is, occasionally, confused with other neoplasm, particulary squamous carcinoma owing to its close cytological resemblance. We report a case of proliferating trichilemmal tumor in the left breast. The patient is a woman and had a lump in the breast for 20 years. Fine needle aspiration revealed a few small clusters of squamoid cells in the background of amorphous and calcified material. After excisional biopsy, the mass was confirmed as proliferating trichilemmal tumor. The main cytologic features discriminating squamous cell carcinoma were bland nature of epithelial cells, absence of atypical dyskeratotic cells, and rich amount of amorphous material.