Fine-needle aspiration cytology of metastatic squamous-cell carcinoma arising in a pilonidal sinus, with literature review

Fewer than 50 cases of carcinoma arising in a pilonidal sinus have been rep orted, with only 5 patients having documented inguinal lymph node metastase s. This is the first report of the fine-needle aspiration (FNA) diagnosis o f this uncommon clinical situation of squamous-cell carcinoma al ising in a pilonidal sinus, metastatic to an inguinal lymph node. We report on a 59-y r-old male with squamous-cell carcinoma arising in a pilonidal sinus who pr esented with inguinal adenopathy. FNA biopsy of a lymph node was performed, resulting in a diagnosis of metastatic squamous-cell carcinoma. FNA biopsy is useful in the evaluation of patients with inguinal adenopathy and a his tory of malignancy arising in a pilonidal sinus. The possibility of this ra re complication should also be considered when metastatic squamous-cell car cinoma to an inguinal lymph node is diagnosed by FNA cytology in patients h aving an unknown primary except for a change in a long-standing pilonidal c yst. (C) 1999 Wiley-Liss, Inc.