Stromal fragments in invasive carcinoma. Source of diagnostic difficulty in aspiration cytology

OBJECTIVE: To analyze three cases of stromal fragments in invasive carcinoma that created diagnostic difficulty in aspiration cytology. STUDY DESIGN: A retrospective review of fine needle aspiration cytology (FNAC) smears of a breast tumor, scalp tumor and neck mass. Cytomorphologic features of all the smears were reviewed after histology became available. RESULTS: FNAC smears revealed a biphasic pattern: a carcinomatous component and a stromal component that was either discrete or in close apposition to the carcinoma. The cytopathologist had suggested the diagnosis of a biphasic tumor in each case--phyllodes, malignant skin adnexal and salivary gland tumor. Histopathology revealed an invasive carcinoma with altered stroma in the first two cases and metastatic lymph node with perinodal soft tissue extension in the third case. CONCLUSION: Stromal changes in response to infiltrating carcinoma are well documented in surgical pathology. However, these may also be encountered in FNAC smears. The above cases stress the importance of recognizing stromal fragments in aspiration cytology in order to avoid diagnostic errors.