Scalp Nodule in an Elderly Woman—Diagnosis

Histopathologic examination revealed islands of atypical basaloid cells floating in an abundance of mucin, consistent with mucinous carcinoma. Primary tumor vs secondary metastatic carcinoma could not be determined on histologic analysis alone. Findings of immunohistochemical stains were negative for CK20, p63, CDX-2, and TTF-1 and positive for CK7. Focally positive findings were found for GCDFP-15 in the target cells.

The CT scan revealed a large soft-tissue mass arising within the left posterior parietal scalp invading the underlying subcutaneous tissue without any bony erosion or periosteal reaction. The patient was seen by a surgical oncologist, but owing to the size of the lesion, she was sent to a radiation oncologist for further evaluation. Suspicion was low for metastatic disease because of the relative stability of the lesion over several years and the patient's overall good health. The patient refused a positron-emission tomographic scan to exclude a primary tumor, and was treated with local radiotherapy. Six months after diagnosis, she had no evidence of systemic disease.