The specimen is hypercellular and comprised of high nuclear to cytoplasmic ratio cells with prominent nucleoli. Anucleated squames are present.
This case is easily misdiagnosed as poorly differentiated squamous cell carcinoma. Clinical presentation in this case was the main clue preventing us from misdiagnosis. The mass was superficial and mobile and was "benign for sure" according to the ENT surgeon who performed the FNA.
The abrupt transition from the high N/C ratio blue cells to anucleated squames, the occasional giant macrophages, and the background calcification (picture 3) are diagnostic clues.
Diagnosis: pilomatrixoma.
The mass was resected and here is the H&E slide:
Pilomatrixoma is a well-known diagnostic pitfall to cytopathologists. It can be misdiagnosed as poorly differentiated carcinoma, adenocarcinoma, small blue cell tumor, etc. It is essential that we are familiar with the cytomorphologic features of pilomatrixoma.
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