Precoccygeal leiomyoma: A rare cause of pelvic and anal pain

Abstract

Precoccygeal tumors are an uncommon group of heterogenous lesions ranging from benign simple cysts to complex malignant masses. Their nonspecific clinical presentations often make diagnosis difficult. Cross-sectional imaging, including computed tomography (CT) and magnetic resonance imaging (MRI), plays a critical role in their detection and characterization. Magnetic resonance imaging is considered the gold standard owing to its superior soft tissue resolution and detailed anatomical evaluation. Surgical excision remains the treatment of choice. Prognosis depends on the tumor’s nature and completeness of resection. Herein, we present the case of a precoccygeal leiomyoma in a premenopausal female patient with episodic, deep-seated pelvic and anal pain that worsened during ovulation.

Introduction

Precoccygeal tumors are a rare subset of presacral lesions that encompass a wide spectrum of pathologies, ranging from benign cystic lesions to aggressive malignant neoplasms. Their clinical presentation is often nonspecific and depends on factors such as lesion size, growth pattern, and relationship to adjacent structures, which can make early recognition difficult. Cross-sectional imaging, particularly magnetic resonance imaging (MRI), plays a pivotal role in characterizing these lesions, delineating their anatomical relationships, and guiding surgical planning. Presacral leiomyomas are exceedingly uncommon, with only a few cases described in the literature [[1], [2], [3]]. To our knowledge, a precoccygeal leiomyoma has not been previously reported.

Case report

A previously well woman in her early 40s presented to her primary care physician with episodic pelvic and anal pain. The pain was described as a dull, low-intensity ache. Symptoms were present for 6 months prior but worsened in severity over the past month. The symptoms were most pronounced during ovulation. The patient had no known medical illnesses and had no prior surgeries. Family history was noncontributary. Her physical examination was unremarkable.

A complete blood count was ordered, with results as follows: Hb—12.1 g/dL (normal range: 11.5-16 g/dL); WBC—4.6 × 10⁹/L (normal range: 4.0-11 × 10⁹/L); Platelets—179 × 10⁹/L (normal range: 150-400 × 10⁹/L); MCV—85 fL (normal range: 78-100 fL); RBC—5.3 × 10¹²/L (normal range: 4.5-6.5 × 10¹²/L).

A contrast-enhanced pelvic MRI was subsequently performed and showed a 2.2 × 2.4 × 2.0 cm circumscribed, rounded precoccygeal mass with intermediate T2 signal and no internal fat or hemorrhage (Figs. 1 and 2), located below the midline levator plane. Fat planes around the coccyx and levator ani muscles were preserved. A multifibroid uterus was also present (Fig. 2). Mild enhancement was noted following intravenous gadolinium administration (Fig. 3). No other significant findings were demonstrated.

Fig. 1.

Axial T2-weighted magnetic resonance imaging (MRI) image of the lower pelvis demonstrating a well-circumscribed, T2-intermediate signal lesion (white arrow) below the midline levator plate.

Fig. 2.

Midline sagittal T2-weighted magnetic resonance imaging (MRI) image of the pelvis showing a well-circumscribed, T2-intermediate lesion (white arrow) located anterior to the coccyx in the inferior-most portion of the presacral space. There are preserved fat planes anteriorly with the rectum and posteriorly with the coccyx. A mildly enlarged anteverted uterus containing several fibroids is also seen (red arrow).

Fig. 3.

Axial T1-weighed images of the lower pelvis before (A) and after intravenous gadolinium with fat suppression (B), showing mild enhancement of the precoccygeal lesion.

A percutaneous ultrasound-guided biopsy was performed using a posterior approach, and samples were sent for histological evaluation. Histology revealed a low-grade spindle cell neoplasm consisting of bland ovoid to spindle cells occurring in short fascicles (Fig. 4). Necrosis was absent. The mitotic count was <1/10 HPF. Immunohistochemical staining was performed for definitive diagnosis and showed that the lesional cells were negative for S100 and CD34, while desmin showed diffuse and strong positivity (Fig. 5). The findings were most in keeping with a smooth muscle neoplasm. Given the minimal mitotic activity, the overall histological features supported a diagnosis of leiomyoma.

Fig. 4.

H&E Stain at high magnification (×400) showing interlacing bundles of spindle-shaped smooth muscle cells with a mitotic count <1/10 HPF and no necrosis.

Fig. 5.

Desmin immunohistochemistry stain (×40) demonstrating strong and diffuse positivity in lesional cells, confirming smooth muscle origin.

General surgery outpatient clinic appointment is scheduled in 2 months for presurgical assessment with a view to complete excision.

Discussion

Precoccygeal tumors are an uncommon subset of presacral tumors, encompassing a heterogeneous range of pathologies from benign simple cysts to complex malignant masses [4]. These tumors arise from the inferior-most portion of the presacral space, bounded anteriorly by the rectum and mesorectal fascia, superiorly by the peritoneal reflection of the sigmoid colon, posteriorly by the presacral fascia, inferiorly by the rectosacral fascia, and laterally by the iliac vessels and ureters, below the level of S4-5 [5].

Presacral tumors are rare, with an estimated incidence of 1:40,000-60,000 hospital admissions. They show a female predilection, with a median age around 45 years. Benign etiology and congenital classification are more frequently observed. Malignant lesions are more prevalent in males and are associated with higher complication and recurrence rates [6].

Several classification systems exist to guide management. Uhlig and Johnson categorized these tumors as congenital, neurogenic, osseous, inflammatory, and miscellaneous, while Dozois et al. further subclassified them as benign or malignant [7,8]. Congenital lesions comprise the majority (55%-70%) and include chordomas, developmental cysts, and anterior sacral meningoceles [9]. Neurogenic tumors, including neurofibromas, ganglioneuromas, schwannomas, ependymomas, neurofibrosarcomas, and neuroblastomas, are the next most common and are typically benign and slow-growing. Osseous tumors grow rapidly and include osteosarcomas, myelomas, and chondrosarcomas. Miscellaneous lesions, as in our case, account for approximately 10%-25% of all presacral tumors and include metastases, fibrosarcomas, lipomas, hemangiomas, lymphomas, liposarcomas, and leiomyomas [8,9].

Their clinical presentation is often nonspecific and depends on lesion size, growth rate, and relationship to surrounding structures. Small lesions may be asymptomatic and incidentally discovered. When large, these lesions produce symptoms related to compression or invasion of pelvic organs or nerves, including lower back pain or perineal pain, constipation, urinary/fecal incontinence, or sexual dysfunction. Malignant lesions and infected benign lesions tend to present acutely with abdominal or lower back pain [4,6].

Cross-sectional imaging plays an important role in diagnosis and management. Computed tomography (CT) and MRI are the modalities of choice in the assessment of presacral masses. CT can help determine whether the lesion is cystic or solid, assess involvement of adjacent viscera, and detect bony destruction [4]. MRI is considered the gold standard for evaluating presacral tumors, providing superior soft tissue resolution and aiding surgical planning by delineation resection planes [6]. MRI can also assess the extent of bone marrow involvement and identify associated spinal cord abnormalities [4].

Differential diagnoses for precoccygeal masses, as in our case, include developmental cysts, such as dermoid cysts, epidermoid cysts, and tailgut cysts. These lesions usually demonstrate fluid density on CT images and fluid intensity (low T1, high T2) characteristics on MRI. Dermoid and epidermoid cysts are usually unilocular, whereas tailgut cysts are usually multilocular. Other differentials include neurogenic tumors, such as schwannomas and neurofibromas. These tumors are usually iso/hypointense relative to muscle on T1-weighted images and heterogeneously hyperintense on T2 images with heterogenous post-contrast enhancement. Neurofibromas may also show a target sign on T2-weighted images. Chordomas should also be considered; however, they often cause bony destruction with intra-sacral involvement and demonstrate both pre- and post-sacral extension. Chordomas show a mixed signal intensity on T2-weighted images [10]. Leiomyomas, as seen in our case, demonstrate variable MR signal and enhancement characteristics; however, they have been described as well-defined masses, which demonstrate isointense signal on T1-weighted images and low signal on T2-weighted images in comparison to skeletal muscle [11].

Surgical excision is the treatment of choice. The role of preoperative biopsy is controversial. Some authors recommend preoperative biopsy when neoadjuvant therapy may be indicated, such as in Ewing sarcoma, osteogenic sarcomas, desmoid tumors, and neurofibrosarcomas [4,6]. Other authors advise against preoperative biopsy due to the risk of infection and tumor seeding along the biopsy tract [2]. Preoperative biopsies performed via transperitoneal, transrectal, or transvaginal approaches may increase patient morbidity, as the biopsy tract must be removed en bloc in cases of malignancy [4].

Complete resection is the treatment of choice for presacral tumors. Three common surgical approaches are employed: the anterior approach (transabdominal), posterior approach (perineal), and combined abdominoperineal approach. The anterior approach is typically used for lesions located at or above the S3 level, with no sacral invasion. The posterior approach is preferred for lesions located below the S3 level, with coccygectomy being performed in the majority of cases. This approach carries an increased risk of hemorrhage but lower risk of damage to neurological structures. The combined abdominoperineal approach is used for masses extending both above and below the S3 level or involving surrounding structures [5].

Prognosis depends on the tumor’s nature and completeness of resection. Benign presacral tumors have a survival rate of 100%, although recurrence may occur depending on the extent of excision. Malignant lesions carry a prognosis proportional to tumor type and resection success [4].

Patient consent

Informed consent was obtained from the patient to use her information in this manuscript.