A rare case of needle tract seeding from colonic adenocarcinoma

A 58-year-old male underwent surgery with curative intent for a pT4aN0M0 colonic adenocarcinoma. A one-year surveillance CT abdomen & pelvis demonstrated an interval onset para-aortic nodal mass with FDG avidity on PET-CT. The node was biopsied and five months later he developed enlarging, painful subcutaneous lesions at the biopsy site.

The surveillance CT abdomen & pelvis one year post left hemicolectomy demonstrated a rim-enhancing, centrally-necrotic, para-aortic nodal mass measuring 5.1 x 4.1 cm (Fig. 1a).

Given his history of malignancy, he underwent a PET-CT which demonstrated FDG avidity (Fig. 1b).

Under direct CT-guidance, 3 x 18 gauge core biopsy samples of this para-aortic lymph node mass were taken, below the level of the renal artery and lateral to the aorta (Figs. 2a & 2b). Histopathology confirmed metastatic adenocarcinoma with features in-keeping with colorectal origins. He commenced chemotherapy.

Five months later, he developed an enlarging, painful, subcutaneous lesion at the site of previous para-aortic node biopsy

Serial CT scans revealed an enlarging mass over the previous biopsy site (Figs. 3a-c), that was suspicious for malignant seeding, and a subsequent PET-CT revealed FDG avidity (Figs. 4a & 4b). Biopsy of the subcutaneous lesion confirmed metastatic adenocarcinoma with colorectal origins.

Tissue histology remains the gold-standard in the investigation and diagnosis of malignancy. Percutaneous needle biopsy (PNB) either via core biopsy or fine needle aspiration (FNA) is considered a safe procedure with morbidity and mortality rates < 1% [1]. However, it is not without risk and needle tract seeding (NTS) is a rare but significant adverse effect, referring to the dissemination of malignant cells along the route of the needle tract used to retrieve a tissue sample [2]. Malignant cells are inherently less adherent to each other due to loss of cell-cell adhesion molecules. This may cause dislodgment during the biopsy process, and facilitate seeding along the biopsy tract, by adhering to the surgical instrumentation [3]. NTS is particularly concerning because malignant spread affects disease staging, therefore prognosis, treatment options and patient outcomes.

Given that NTS generally presents with painful subcutaneous deposits [4], and in this case, the painful lesion occurred at the entry site of his previous biopsy, suspicion for NTS was raised. Malignant deposits tend to be round or oval, with well-defined margins, and display varying levels of enhancement following intravenous contrast media [5].

Various hypotheses have been suggested as risk factors for NTS including; the biopsy technique itself, with co-axial systems thought to reduce risk of NTS [6], reduced number of needle passes [4,7] and traversing fewer tissue planes during the biopsy [3]. In this case, our patient’s para-aotic lymph node biopsy was carried out with standard technique using an 18-gauge X 16cm BARD core-biopsy needle set with 3 passes.

In addition to the biopsy technique, tissue-specific risk factors play a role in NTS, as noted by the variation in NTS incidence depending on the tissue site being biopsied: incidence as low as 0.01% reported for renal cell carcinoma [8] and as high as 2.7% reported for hepatocellular carcinoma [9]. To the best of our knowledge there are no reports of NTS from a para-aortic lymph node of colorectal origins.

In our tertiary-level hospital, the interventional radiology department carries out approximately 900 core biopsies annually, for the investigation of potential malignancy. To date, this is the first confirmed case of NTS at our centre.

In summary, we present the rare case of needle tract seeding from a para-aortic lymph node of colorectal origins. While a relatively safe procedure, percutaneous needle biopsy is not without risk of iatrogenic NTS and the risk:benefit should be considered in the context of each individual patient.

Written informed patient consent for publication has been obtained.