Cutting the Gordian Knot: Rare Presentation of Nodular Fasciitis as Supraclavicular Swelling with Muscular Involvement in 68Ga-FAPI-PET/CT

Figure 1. Sonographic findings: (A) Sonographic visualization of the lesion using a linear transducer probe at 14 MHz; (B) Doppler sonography shows diffuse perfusion. (C) In-plane view of the core needle biopsy showing the biopsy channel (orange arrows indicate the intratumoral biopsy tunnel). Pictograms on the right of the image show the sonographic cross section. Nodular fasciitis is a benign, reactive lesion characterized by rapid growth and fibroblastic/myofibroblastic proliferation. It is frequently misdiagnosed as a soft tissue sarcoma due to its rapid, infiltrative growth pattern, high cellularity, and increased mitotic activity [1]. It was first described in 1955 by Konwaler et al. [2] We present a case of a female patient to emphasize the importance of considering this differential diagnosis in the context of rapidly progressing masses in the head and neck area. In our case, a 40-year-old, otherwise healthy female patient presented to our outpatient clinic with an unclear nodular lesion in the right supraclavicular region. The ENT examination findings of the ears, nose, nasopharynx, oropharynx, hypopharynx, and larynx were unremarkable. Sonographically, a coarse, poorly…

Figure 2. Histological HE staining of the tissue samples: (A) 10× magnification of the surgical tissue sample. (B) 40× magnification of the surgical tissue sample. Typical variable myxoid changes and extravasated erythrocytes as well as elongated cells with oval, slightly enlarged cell nuclei and loosened karyoplasm are visible. The core needle biopsy was technically challenging due to the anatomical location near the brachial plexus and lung apex. Initial light microscopy findings were nonspecific, raising the possibility of a sampling error where only non-representative peripheral areas of the lesion may have been obtained. Therefore, definitive histological confirmation through open biopsy was pursued, as shown in Figure 2.

Figure 3. Preoperative CT staging: (A) The arrow points to an intratonsillar lesion; the differential diagnosis initially included an abscess and a malignant, centrally necrotizing lesion. (B) The arrow points to the radiologically suspicious supraclavicular mass with muscular infiltration in the sternocleidomastoid muscle. The subsequent CT staging examination revealed, in addition to the already sonographically depicted 3.5 cm × 3 cm supraclavicular mass, a hypodense 5 mm intratonsillar lesion on the right side. This constellation of findings supported the suspicion of a possible p16-positive tonsillar carcinoma with supraclavicular lymph node metastasis, although this would have been an atypical metastasis localization. Based on these findings, diagnostic panendoscopy with biopsy of the right tonsil and sonographically guided excision of the right supraclavicular mass was indicated during the interdisciplinary head and neck tumor conference. The intraoperatively obtained frozen section from the tonsil could not exclude malignancy (Figure 4). Subsequently, exploratory excision of the supraclavicular mass was attempted. Intraoperative exploration of the surgical site revealed the full…

Figure 4. Intraoperative enoral findings: (1) shows the enoral course of the tube. (2) shows the median uvula. (3) shows the intraoperative findings of the right tonsil lobe after trial excision. Given the unresolved nature of the lesion’s dignity, the indication for 68Ga-FAPI-PET/CT was determined during the interdisciplinary head and neck tumor conference decision. This imaging modality was employed both for further lesion characterization and as part of pre-therapeutic staging. Comprehensive tumor assessment was conducted to identify potential metastases not detected by conventional CT staging. This showed intensive uptake in the previously described supraclavicular lesion and a reactive tracer accumulation at the biopsy site of the right tonsil. No other systemic lesions were detected (see Figure 5). The definitive histological RNA-based NGS analysis provided evidence of the MYH9-USP6 fusion. Recent studies suggest that the fusion of the MYH9-USP6 genes leads to the overexpression of the USP6 protein in 83–92% of cases, which acts as a pro-oncogene [3,4]. Microscopic histomorphological imaging confirmed the diagnosis of nodular fasciitis. The final findings of the oral lesion ruled out…

Figure 5. Postoperative 68Ga-FAPI-PET/CT: 14 days after the operation, a whole-body PET/CT was performed with 167 MBq 68Ga-FAPI-04. Images were acquired 16 min post-injection (2.5 min per bed position). The examination showed a tracer accumulation intratonsillar on the right (blue arrowheads), primarily in the context of postoperative changes. Intense uptake in the supraclavicular mass on the right (red arrowheads); otherwise physiological tracer distribution (among others in the uterus); (left): maximum intensity projection (MIP); (right): representative transversal and coronal slices. Our case presents the course of a patient with a rapidly progressive mass in the head and neck region. Due to initially unclear findings and the more common malignant lesions in this area, malignant differential diagnoses such as sarcoma and squamous cell carcinoma were considered. The subsequent diagnostic and surgical procedures represented a major psychological burden for the patient and her family. Other working groups reported comparable diagnostic workups [6]. If there is doubt about excluding malignancy, complete removal of the tumor along with selective neck dissection can be a safe option with…