Tumors of the anterior abdominal wall constitute a rare class of neoplasia. A very important aspect of this clinical case is the unpredictability of its onset, making it unique and rare, being the case of a rare condition mimicking another rare conditions hence the need to describe it. In fact, the incidence of abdominal soft tissue sarcoma is about 2.8 cases per million per year (less than 5% of all soft tissue sarcomas) [
1] similar to that of desmoid tumors, i.e., 2–4 cases per million per year [
11], and the present case seems to be the first described in the literature. Desmoids preferentially develop in women of fertile age, especially during pregnancy and in puerperium. Hormonal factors such as pregnancy-related hyperestrogenism may favor their formation [
3]. Since they may arise more frequently in the puerperium, traumas or microtraumas to the abdominal wall with consequent tissue correction may cause their onset [
3]. Furthermore, surgery and inflammation may induce tumor growth. Typically, wound healing is a strictly controlled, self-limited process of tissue regeneration and remodeling. In response to tissue injury, mesenchymal cells are recruited to promote wound healing [
12]; these pluripotent cells differentiate into fibroblasts, myofibroblasts, and endothelial cells. Therefore, the phenomena of repair, cicatrization, correction, and healing may lead to a series of events causing desmoid tumors, especially in people with a genetic predisposition to beta-catenin deregulation [
11].
The present case showed a completely different clinical phenomenon. Although the symptomatic and growth characteristics of the neoformation resembled those of a desmoid tumor, the PET findings were positive, with a very high SUV. This influenced our presurgical diagnosis. In fact, desmoids are unlikely to be PET positive due to their low mitotic index, and if they are (but rarely), the SUV is very low [
13]. One could also hypothesize a sarcoma caused by the sarcomatoid degeneration of residuals of the previous myomectomy. When a myomectomy is performed in confined spaces with the need for morcellation, the spillage of tissue components may occur, which over time, following adequate stimuli, may evolve into disseminated myomatosis and, in more serious cases, sarcomatoid degeneration [
6]. However, in our case, the preoperative biopsy did not confirm the suspicion of sarcoma but rather reinforced the hypothesis that it could be an atypical desmoid due to its high SUV index. According to the international guidelines [
1], we performed a total surgical excision of the neoplasm. The definitive histology showed an extremely complex and rare problem; the desmoid nature was not confirmed (the lymphomonocytic component was prevalent, beta-catenin was negative, and the beta-catenin gene was wild type), but a foreign body granuloma was diagnosed. The foreign body consisted of amniotic fluid and meconium, suggesting either an inadequate cleaning of the cesarean incision site during suturing or, more probably, that these residuals triggered the generation of such peculiar inflammatory response in a likely predisposed woman. In fact, many women are exposed to meconium and amniotic fluid at the time of cesarean section, and the majority of them do not develop such an atypical inflammatory reaction. A foreign body reaction is usually characterized by inflammatory cell infiltration of mainly macrophages with foreign body giant cells, fibroblast activation, and peripheral fibrosis [
14]. Macrophages have specific roles, including M1 or M2 polarization and the consequent difference in the storage of collagen and fibrosis [
15]. At this regard, it should be emphasized our decision to proceed with the immunofluorescence analysis of the pseudotumor tissue by flow cytometry. We performed this peculiar, but greatly belonging to our research expertise [
7], assay specifically to understand the origin of the PET glucidic hypermetabolism and to better define the inflammatory component, considering that the intraoperative histology excluded the diagnosis of sarcoma. In our case, the analysis of the cell phenotype by flow cytometry demonstrated that M1-polarized Glut+ macrophages were the most dominant cell subsets. Therefore, the positive PET finding was certainly correlated to the high number of inflammatory cells, particularly CD14/Glut+ cells with high glucose uptake; meanwhile, the CD13+ and CD10+ cells were Glut−. These results confirm that the neoformation was an early granuloma that rapidly arose as a reaction to the spillage of meconium and keratinous material (vernix caseosa) present in the amniotic fluid in the subcutaneous tissue during cesarean section. The literature reports very rare cases of similar clinical conditions [
16,
17], referred to as “organizing peritonitis, which included prominent collections of anucleate squamous cells in association with a foreign body-type granulomatous response” [
16]. To our knowledge, this is the first case described in the literature.