A 22-year-old man visited The West China Hospital of Sichuan University presented with a 3-year history of two progressive growing masses on the abdominal wall,one on the lower abdominal wall and the other on the right abdominal wall.These two masses protrude from the surface of the body without pain, itching, ulcers, or other symptoms.
When he was 17, he had his first operation at a local hospital to excise a soybean-sized mass on the lower abdominal wall in the fat layer, which was pathologically diagnosed as a “fibroma”.
But a mass was found again at the healing site of the original surgical incision only 8 months later, protruding body surface, and gradually grew to the size of 6.5×3.2cm. He visited another hospital asked for surgical treatment, the scope of surgical resection is still did not reach the anterior rectus sheath, however, due to the mass size is larger, the incision was wide and direct suture was difficult, so a medium thickness flap was taken from the right abdominal wall and transplanted to cover the incision at the lower abdomen. And he did not receive adjuvant therapy after operation. Postoperative pathologic report indicated spindle cell proliferative, in addition, there was no tumor invasion in the perioperative margins and basement of the surgical specimen.Further immunohistochemistry was performed and the results showed that:SMA (+), Desmin (-),S-100 (-), CD34 (-),β-catenin (-), TLE-1 (-), EMA (-),Ki-67 (the positive rate was about 2%).
Due to the lack of clear diagnosis of DTF in the previous two visits to the hospital, the patient did not pay enough attention to the disease, so he did not receive regular follow-up.
Unfortunately, 3 years later, a recurrent mass was found in the lower abdominal incision, and it was larger than the one excised the second time, strangely, at the same time, a new,large and hard mass appeared in the incision of the right abdominal wall. Then, he came to plastic surgery department of our hospital(Fig.1) and underwent an enhanced magnetic resonance imaging (MRI) examination of abdomen(Fig.2A-F). It showed multiple soft tissue masses and nodules in the subcutaneous fat layer of the lower abdomen and right abdomen. T1WI(T1-weighted imaging) showed homogeneous medium signal, T2WI(T2-weighted imaging) showed low signal, uneven reinforcement after enhancement, the mass of lower abdominal wall grew invasively to the deep, part of which was not clearly demarcated from the anterior sheath of rectus abdominis, and the adjacent muscle fibers and fascia were thickened and enhanced. The radiologist considered the diagnosis of abdominal fibrosarcoma.
In view of the slow growth, no obvious boundary, tough texture, and no obvious necrotic foci observed on MRI, the masses is not fully consistent with the clinical characteristics of fibrosarcoma. At the same time, in order to confirm the pathological results of the two previously resected masses of the patient, we required the patient to go to the hospitals where he visited at that time to extract the paraffin section specimen for pathological consultation in the Pathology Department of West China Hospital. After consultation, the pathological results of the first two excised mass indicated that the spindle cell proliferative lesion supported the histological morphology of desmoid fibromatosis(Fig.3A,B).
For a definitive diagnosis, then we took some tissue from each of these masses and did a pathological examination(Fig 3C,D). The pathological report indicated that the two lesions were consistent, both were spindle cell proliferative lesions and fibrogenic tumors, scar tissue can be seen in some superficial areas (consistent with keloid). Further immunohistochemical analysis results were as follows: the pathological cells showed desmin (-), SMA (+), β-cantenin (nuclear -), myo D1 (-), CD34 (-), EMA (-), TLE-1 (-), MUC-4 (-). CTNNB1 gene mutation: Exon3 mutation was not detected. The histological morphology of the two masses previous resected was reviewed, which was consistent with the specimen sent for biopsy, the final diagnosis was desmoid fibromatosis through comprehensive analysis.
After the definitive diagnosis, we detailed the risks associated with surgery and recurrence of the masses to the patient and signed an informed consent form for the operation. Considering that the two tumors were too large, the enlarged resection might be directly difficult to suture, and if the skin flap was transplanted to cover the wound, a new tumor might appear in the donor area again, so we chose to excise the tumor along the edge of the tumor. Intraoperatively, it was found that the mass of the lower abdominal wall was mostly located in the adipose layer, and a small part of the mass in the deep side invaded the anterior sheath of rectus abdominis. Therefore, we excised the invaded anterior sheath of rectus abdominis, and no invasion of muscle tissue was observed(Fig.4A-C). The right abdominal wall mass(RAWM) only extends to the adipose layer. We excised the mass completely but did not excise a portion of scar tissue on the right abdominal wall that did not touch the obvious mass(Fig.4D-F), then sutured both incisions directly. The patient was discharged from hospital after incision healing(Fig.5).
The pathological result showed that both tumors were subcutaneous, grayed white cut surface, solid and tough texture. The diagnosis of desmoid fibromatosis was still considered in combination with the biopsy result(Fig.6A,B).
The surgical incisions healed and sutures were dismantled 15 days after surgery, then he went to the oncology department and received radiation therapy. Image guided IMRT(Intensity-modulated radiation therapy) method was adopted. The radiotherapy regimen was described below:D95% CTV(clinical target volume)1,2(Postoperative tumor bed area) 1.5Gy/fraction,bid(bis in die).The radiotherapy went smoothly 30 times. The patient developed an ulcer on the skin of the lower abdominal wall after radiotherapy,which healed after active dressing change.
In general, DTF did not have the ability to metastasize,but the emergence of the mass in the right abdominal wall caught our attention. We extracted paraffin sections of the two surgical specimens from the Department of Pathology. After evaluating the paraffin samples, it was concluded that whole-genome sequencing might not be as effective as expected, we finally chose the relatively effective whole exon sequencing.
The sequencing results as follows: the SNV(single nucleotide variant) mutaition and the InDel (insertion and deletion) mutation of the two masses were very similar(Fig. S1), and the consequence of the tumor variant types were similar(Fig. S2).
After mutation filtration,a total of 41 somatic SNV and InDel mutations were found in paraffin section samples of right abdominal wall mass(RAWM), and 20 in lower abdominal wall mass(LAWM), due to there were fewer high quality somatic cell mutations detected, we tested the homology of the two masses according to the method reported in previous study[14]. Somatic mutations in the two samples contained 13 non-synonymous mutations in RAWM and 6 non-synonymous mutations in LAWM. And there were 4 shared mutations between the two samples(Fig.7). Shared mutations occupy 30.8%(RAWM) and 66.7%(LAWM) of the two samples, respectively. According to the reporting criteria, there was more than one shared mutation, so it can be judged as a implantative metastasis.
Six months after the radiotherapy, abdominal MRI reexamination showed a small amount of enhanced signals in the operative area, scar tissue was considered, and no obvious tumor recurrence was observed. During regular follow-up of patients,the patient's abdominal wall was in good condition and no neoplastic mass was observed in the operation area and follow-up is continuing.