The role of ultrasound-guided needle biopsy in the diagnosis of soft-tissue tumors

Abstract

Soft-tissue tumors are not very common, but their diagnosis can be very difficult. In the final analysis, their diagnosis requires a biopsy, which must furnish a sufficient amount of material to allow a reliable histological diagnosis. The authors evaluated the diagnostic efficacy of ultrasound-guided needle biopsy in the diagnosis of soft-tissue tumors of the musculoskeletal system. The aim of the study was to optimize the biopsy procedure, with particular emphasis on the choice of the biopsy needle (large-gauge manual versus semiautomatic) based on the characteristics of the neoplastic mass (consistency, depth, size, location). The results of the study showed that appropriate needle selection significantly reduced the frequency of biopsies that were insufficient for histological diagnosis. The method proved to be highly reliable for diagnosis of soft-tissue tumors but strongly related to the proper selection of the needle to be used.

Introduction

Soft-tissue tumors are not very common, but their diagnosis can be very difficult [1]. The final diagnosis requires a biopsy, which must provide sufficient material for a reliable histological diagnosis.

Ultrasound-guided needle biopsy can be used to collect samples of soft-tissue masses [2], even when the lesion is small or in a difficult location (close to blood vessels or nerves that might be damaged or in areas where maneuverability is limited, e.g., near joints or tendons).

To provide sufficient material for a reliable histological diagnosis, multiple biopsies must be collected from all potentially viable areas of the lesion.

The needle-insertion pathway should coincide with the surgical access pathway to eliminate the risk of neoplastic seeding. For this reason, it must be planned with the aid of the orthopedic surgeon.

To improve the percentage of diagnostic biopsies [3], the authors reviewed their experience over the past two years, evaluating the procedures used, the operative strategies adopted, and the instruments that proved to be most effective.

Materials and methods

Over a period of two years (June 2004 through July 2006), our staff performed 185 ultrasound-guided needle biopsies: 164 involved soft-tissue lesions (primary, metastatic, or recurrent) [4] and the remaining 21 involved lesions originating in the bone and extending into the adjacent soft tissues.

The latter 21 lesions were excluded from this study since they could not be fully examined with ultrasound.

We thus considered only the 164 patients with lesions originating in the soft tissues. Eighty-nine (54.2%) of these were males and the other 75 (45.8%) were females. The mean age was 48 years (range 5–84 years) (Fig. 1).

Fig. 1.

Histogram showing age-group distribution of study patients.

Each patient underwent a preliminary ultrasound study with color Doppler to define the characteristics of the lesion (location, depth, size, echostructure, vascularization, consistency). With the aid of the orthopedic surgeon, the insertion pathway for the biopsy needle (Fig. 2) was then selected so that it would coincide with that of the surgical access, thus limiting the risk of seeding. A sterile field was prepared, and the biopsy was collected using manual 14- and 18-gauge needles and semiautomatic 13–14-gauge needles (Fig. 3); the site chosen for the biopsy was marked with a dermographic pen.

Fig. 2.

Sterile instrument stand with biopsy needle.

Fig. 3.

Selection of the access pathway under ultrasound guidance.

Ultrasound guidance was used to insert the needle for administration of anesthesia and that used for the biopsy in order to avoid damage to blood vessels and nerves and to ensure correct placement of the biopsy needle (Fig. 4a, b). At least 3–4 tissue samples were collected from each lesion (Fig. 5). Areas of necrosis were avoided to ensure that the pathologist would have abundant tissue to examine. (The diagnosis of soft-tissue tumors is, in fact, based on histology, not cytology) [4].

Fig. 4.

(a) The biopsy is carried out under ultrasound guidance. (b) Ultrasound visualization during tissue collection.

Fig. 5.

Biopsy material collected.

We analyzed the results obtained during two periods of the study (period 1, June 2004 through June 2005, and period 2, July 2005 through July 2006), which were distinguished by the types of biopsy needles being used [5].

Results

Sufficient material for histologic diagnosis was collected in 148/164 cases (90%) of soft-tissue tumors; in the remaining 16 cases (10%), the tissue collected was insufficient.

In the 148 cases in which histological diagnoses were possible, the lesion proved to be benign in 69 (47%) and malignant in 66 (45%); in the remaining 13 cases, the diagnosis was complex due to difficulties encountered in interpreting the pathology findings. Among the benign lesions, the most common diagnosis was aggressive fibromatosis (12 cases), followed by lipoma (11 cases), elastofibroma (7 cases), angioma (6 cases), pigmented villonodular synovitis (5 cases), schwannoma (5 cases), neurinoma (2 cases), etc. The most common malignant lesions were sarcomas (synovial/epithelioid/alveolar) (33 cases), followed by liposarcomas (13 cases), metastases (6 cases), fibrosarcomas (2 cases), leiomyosarcomas (12 cases), Ewing sarcomas (2 cases), etc. The site-related distribution of the lesions is shown in Fig. 6. The vast majority were located on the lower limbs (59%), particularly on the thigh (37%). Others were located on the arm (25%), the interscapular region of the back (7%), the pelvic region (6%), or rarer sites (3%) like the abdominal or chest wall.

Fig. 6.

Distribution of soft-tissue tumors by location.

Discussion

In 16 of the 164 cases of soft-tissue tumors, histological diagnoses could not be made due to insufficient biopsy material. Thirteen of these cases (8%) were examined during the first year of the study (June 2004 through June 2005). Only three (2%) were biopsied during the second half of the study (July 2005 through July 2006). The marked drop in the rate of nondiagnostic biopsies coincides with a change in the type of biopsy needle used by our staff. Biopsies done during the first half of the study were performed with manual small-gauge needles (15–18 gauge) whereas during the second period, we used larger-gauge manual needles (14 gauge) or semiautomatic needles (13–14 gauge), which considerably simplified the biopsy procedure.

The needle was selected based on the type of lesion being examined [6]. Manual needles were used for firm, deep-seated, nonmobile lesions, while semiautomatic needles were preferred for softer masses with semiliquid contents or a mucinous component that were small and located close to the surface.

Conclusions

Ultrasound proved to be an effective tool for real-time visualization of the biopsy procedure. It allowed us to perform the biopsy without damaging arteries, veins, and nerves, including those that were immediately adjacent to the lesion, and to avoid the collection of necrotic tissues.

Ultrasound-guided biopsies are both rapid and repeatable, and patients are not exposed to any form of ionizing radiation. The only drawbacks encountered [7] are related to the presence of shadow zones in the vicinity of bones or extensive areas of calcification, or to difficulties arising in the study of deep-seated tumors with a high content of fibro-adipose tissue. In these cases, strong attenuation of the ultrasound beam results in poor visualization of biopsy maneuvers.

Based on our experience, we feel that ultrasound-guided needle biopsy is a highly reliable tool for the diagnosis of soft-tissue lesions. The results are strongly dependent on the type of needle used: the choice (manual needles versus large-caliber semiautomatic needles) has to be based on the type of lesion being biopsied.