Fine-needle aspiration of basaloid squamous carcinoma: a case report with review of differential diagnostic considerations.

Basaloid squamous carcinoma is a distinct variant of squamous carcinoma with a particularly poor prognosis. To our knowledge, there are only two papers in the cytopathology literature which describe this entity. We report the fine-needle aspiration findings of an additional case of metastatic basaloid squamous carcinoma in a cervical lymph node and compare its cytomorphologic features to those observed on touch imprints of the subsequent surgical specimen. Smears of the aspirate showed a mixed lymphoid background with interspersed cohesive clusters of small cells roughly 3 times the size of small mature lymphocytes. Some cells were angulated and others exhibited irregular nuclear contours. The cells were generally hyperchromatic with evenly staining dense chromatin or irregularly distributed coarse chromatin. Focally there was evidence of nuclear molding. On Diff-Quik staining, irregular globules of magenta-stained extracellular dense material were noted within or adherent to the periphery of some clusters or as somewhat linear formations with small epithelial cells clinging to the edges. Abundant mitotic figures and clumps of necrotic tumor were more apparent on touch preps of the subsequent surgical specimen. The differential diagnosis by fine-needle aspiration includes adenoid cystic carcinoma, basal-cell adenocarcinoma, adenosquamous carcinoma, and small-cell carcinoma. If a fine-needle aspirate of a cervical lymph node shows the features described above and the primary tumor is unknown, suggesting the possibility of metastatic basaloid squamous carcinoma may aid clinicians in the search for a primary site, as basaloid squamous carcinoma occurs most frequently at the base of the tongue, hypopharynx, and supraglottic larynx.