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 reported, with only 5 patients having documented inguinal lymph node metastases. This is the first report of the fine‐needle aspiration (FNA) diagnosis of this uncommon clinical situation of squamous‐cell carcinoma arising in a pilonidal sinus, metastatic to an inguinal lymph node. We report on a 59‐yr‐old male with squamous‐cell carcinoma arising in a pilonidal sinus who presented 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 history of malignancy arising in a pilonidal sinus. The possibility of this rare complication should also be considered when metastatic squamous‐cell carcinoma to an inguinal lymph node is diagnosed by FNA cytology in patients having an unknown primary except for a change in a long‐standing pilonidal cyst. Diagn. Cytopathol. 1999;20:367–370. © 1999 Wiley‐Liss, Inc.