Although studies have reported tumors occurring in the genital region, the etiology of CA is not fully understood [7]. Lane et al. reported a possible link between long-term estrogen therapy and CA development [8]. Some researchers have also proposed that CA arises from the differentiation of fibroblasts or myofibroblasts. Fluorescence in situ hybridization and other analytical methods have been used to reveal deletions in the chromosomal region 13q14 in cases of CA, spindle cell lipomas, and mammary and vaginal myofibromatous tumors [9]. The similar histopathological features observed in this study suggest a potential link between these tumors [10].
Although CA mainly affects the vulvar, vaginal, and scrotal regions, rare cases have been reported in the oral mucosa, male pelvis, subcutaneous tissue of the chest wall, nasopharynx, retroperitoneum, and anorectal region [11–15]. CA is a well-circumscribed benign mesenchymal tumor, often located in the superficial soft tissues of the trunk [6]. Most cases of CA present as asymptomatic subcutaneous nodules, except for those in the nasopharynx and retroperitoneum. In the nasopharyngeal region, the tumor manifests as frequent epistaxis (nosebleeds) and persistent nasal congestion [12], whereas retroperitoneal tumors cause pain in the iliac fossa [2]. In this report, we presented the second known case of CA in a female pelvis with atypical clinical characteristics, manifesting only as mild lower abdominal pain.
The histopathological changes in CA include the presence of a well-circumscribed tumor located within the dermis and lacking a capsule [7]. In most patients, the neoplastic cellular component is predominant, with short, bluntly rounded spindle-shaped nuclei and sparse cytoplasm with indistinct cell borders. Additionally, medium-sized, thick-walled blood vessels with hyaline degeneration, slender collagen fiber bundles, and enlarged histiocytic cells are prevalent in this condition. Pseudo-vascular clefts may occasionally be observed, and mature adipocytes are often present. Similar to other tumors, focal cellular atypia was described in this report, and sarcomatous changes were also identified. IHC revealed that the tumor cells exhibited diffuse vimentin positivity, and CD34 was positive in most cases [7]. In female patients, some tumor cells showed partial positivity for estrogen receptor and progesterone receptor, while SMA, desmin, and S-100 were generally negative. However, in male patients, SMA, muscle-specific actin, and desmin may show partial positivity. The Ki-67 proliferation index is low.
CA often appears as a well-circumscribed, hypervascular tumor on CT or MRI images, with no other specific radiographic findings. It requires differentiation from the following conditions. ① Spindle cell lipoma: This tumor predominantly occurs in the posterior neck, shoulder, and upper back of males. The tumor comprises mature adipocytes and slender spindle cells in varying proportions, with myxoid degeneration in the stroma forming pseudo-vascular spaces. Spindle cells are CD34 positive, and mature adipocytes are S-100 positive. ② Angiomatoid fibrous histiocytoma: A soft tissue tumor that commonly occurs in the external genitalia and perineal region, histologically characterized by multi-cellular and hypocellular areas, with prominent myxoid changes in the hypocellular areas. The tumor cells are epithelioid or spindle-shaped, clustered around blood vessels, and often multinucleated, with transparent or pink cytoplasm. They show strong positivity for desmin and vimentin. ③ Retroperitoneal neurofibroma: It is located along the sympathetic ganglia in the paravertebral region. These tumors are well-circumscribed and variable in size, showing positivity for S-100. ④ Aggressive angiomyxoma: This tumor, often 10 cm or larger in diameter, exhibits infiltrative growth. It is composed of small spindle or stellate cells with lightly stained cytoplasm set within a myxoid matrix. These tumor cells express SMA and desmin; ⑤ Labial Leiomyoma: This tumor consists of fascicles of spindle cells with well-defined cytoplasmic borders and cigar-shaped nuclei, which are positive for SMA [16].
Diagnosing CA based on clinical symptoms and imaging findings before surgery is challenging due to the absence of specific signs. Definitive diagnosis depends on needle biopsy or surgical excision followed by pathological examination. However, CT or MRI can indicate the extent of the tumor and guide the best surgical approach for complete lesion removal.
In summary, CA, although rare in the pelvic cavity, should be considered in the differential diagnosis of hypervascular pelvic space-occupying lesions. Most cases of CA exhibit benign behavior and are easily excised without showing atypia, and follow-up studies show low recurrence and no metastatic potential [17–19]. However, Hanae et al. suggested that previous research might have underestimated the recurrence or metastasic potential of CA, particularly in specific populations such as pregnant women, emphasizing the need for long-term follow-up studies [2]. The limitation in this case is the short follow-up period.