Fine-needle aspiration of low-grade adenosquamous carcinomas of the breast: a report of three new cases.

Objectives: To describe cytology patterns in low-grade adenosquamous carcinomas (LGASCs) of the breast.

Study Design: Low-grade adenosquamous carcinomas of the breast are a recently described rare variant of primary metaplastic carcinomas characterized by clinical indolence, slow evolution and excellent survival. To date, only 7 cases of LGASC were studied cytologically, and it was demonstrated that LGASC identification was difficult because its cellular components exhibited unspecific and nonsuspicious features. They consisted of irregularly clustered cells without prominent cytonuclear atypia, mitosis or necrosis. The presence of metaplastic cells or keratin debris was helpful in accurate tumor typing. We report here 3 additional cases of LGASC that were initially studied by fine-needle aspiration.

Results: We have also encountered diagnostic difficulties and misdiagnosed tumors, since 2 cases were underdiagnosed as 'suspicious' and only 1 was accurately diagnosed as malignancy.

Conclusion: The review of our cases and the literature confirms that, despite its putative metaplastic origin, LGASC is an entity which is difficult to diagnose using classical cytological methods. Moreover, core-needle biopsy as well as frozen sections may also misdiagnose LGASC as a benign breast lesion.