Scalp metastasis of pulmonary blastoma-a rare entity: Cytomorphology with differential diagnoses

Pulmonary blastomas are exceptionally rare tumours. These tumours behave aggressively, with a propensity to metastasise to the brain and mediastinum. A definitive diagnosis of pulmonary blastoma is challenging to obtain on cytomorphology alone.

We herein describe a case of a 59-year-old female who presented with a scalp lesion. The patient was diagnosed to have pulmonary blastoma on histopathology of left lower lobectomy specimen. Fine needle aspiration cytology was done from this recently developed scalp swelling. Cytomorphology supplemented with immunocytochemistry on cell block confirmed the diagnosis of a metastatic pulmonary blastoma.

In a known case of primary pulmonary blastoma, any newly developing lesion at any anatomical site should be carefully evaluated for metastasis. If metastasis is needled and no previous histology is available, it carries a reasonable risk of erroneous interpretation. It is essential not to overlook often subtle biphasic malignant cells on the smears, which otherwise resemble other poorly differentiated tumours. Immunocytochemistry coupled with morphology is confirmatory.