Tubulolobular carcinoma of the breast with grooved and cerebriform nuclei: failure to identify this specific subtype in a case during routine fine needle aspiration cytology and histopathological diagnosis.

Tubulolobular carcinoma (TLC) is a rare tumor of the breast in which histologic features of both tubular and lobular carcinoma are combined. We report a case of TLC, in which the specific subtype was missed at routine cytologic and histopathological examination. A 69-year-old woman presented with a right breast lump. Imaging studies indicated a malignant lesion in right upper quadrant. Routine fine needle aspiration (FNA) cytology diagnosis was a duct cell carcinoma (small cell type). In a setting of cystic thyroid lesions, presence of excessive nuclear grooves, and rare intranuclear cytoplasmic inclusion, metastatic papillary thyroid carcinoma was also considered. However, both these possibilities were not supported by immunocytochemical findings (estrogen receptor+, thyroglobulin-, and chromogranin-). The histopathology diagnosis was invasive duct cell carcinoma. Review of FNA smears and paraffin sections led to the diagnosis of TLC, which was supported by positive immunohistochemical stainings for markers like e-cadherin and β-catein.