Cutaneous Metastasis: A Study of 138 Cases Diagnosed by Fine-Needle Aspiration Cytology.

Background: Cutaneous metastases can occur in a wide variety of internal malignancies and may be the first sign of a clinically silent visceral cancer.

Study Design: A retrospective analysis was made of 138 cases diagnosed with cutaneous and subcutaneous metastasis on fine-needle aspiration cytology (FNAC). Primary tumors of the skin/subcutis were excluded.

Results: Of 138 cases, the primary was known in 101 cases and unknown in 37 cases. The age of the patients ranged from 5 to 86 years, and 76 (55.1%) were male and 62 (44.9%) were female. Clinically, the most common lesion was a single nodule (n = 77, 55.8%). The chest wall was the predominant site (n = 53, 38.4%). In males and females, the most common primary sites were the lung (n = 16) and breast (n = 24), respectively. On cytology, the most common diagnosis was metastatic adenocarcinoma (n = 41, 29.7%). Of 37 cases with an unknown primary, FNAC helped to locate the primary site in 17 (45.9%) cases, while in 20 cases it remained undiagnosed.

Conclusions: FNAC is a rapid and safe technique that can be used as a first line of investigation for confirmation of metastatic lesions of the skin. Critical evaluation of cytomorphological features along with relevant clinical details could help in the localization of an unknown primary site in some cases.