A 55 year old man presented with 5 year history of recurrent pilonidal sinus disease located in the sacrococcygeal region. MR with preoperative biopsy and postoperative pathohistological analysis were performed.
A 55 year old man presented with 5 year history of recurrent pilonidal sinus disease located in the sacrococcygeal region.
Plain radiography of the sacrum revealed osteolythic destruction of the sacrum.
MR revealed pathological substrate located in sacral region, isointense to skeletal musculature on T1-weighted images and heterogeneously hyperintense on T2-weighted images. Pathological substrate involved sacrum from S2 segment to coccygeal bone, with destructive lesions of both bones, spreading through sacral foramina into the spinal canal, dorsally infiltrating gluteal musculature, subcutaneous tissue and cutis. Ventrally pathological substrate infiltrated fatty tissue of ischiorectal fossa and dorsal wall of the rectum. Multiple cutaneous fistulas in sacral region were depicted. T1-weighted gadolinium post-contrast images showed heterogeneous enhancement of substrate with areas of very high signal intensity pertaining to hypervascularization of granulation tissue in combination with neoplastic process.
Preoperative biopsy and postoperative pathohystological analysis diagnosed well-differentiated squamous carcinoma of the sacrum and sacral region without lymph node involvement.
Sacral resection en bloc and anus praeter were performed following radiotherapy treatment.
Pilonidal sinus disease is a common disease that affects men more than women, presenting with pain and tenderness, sanguino-purulent discharge, overgrowth and ulceration in the sacrococcygeal region [1]. There are two theories regarding the pathophysiology: the first is congenital-genetic aetiology; and the second relates to ingrowth of hair in the dermis in the intergluteal cleft with foreign body reaction and chronic inflammation [2]. Common complications are infection, abscess, and recurrent sinus disease after surgery; less common are sacral osteomyelitis and meningitis. Malignant transformation occurs in approximately 0.1% of patients with recurrent pilonidal disease. Majority of the malignances are squamous cell carcinomas, extremely rare are basal cell carcinomas, adenocarcinomas and verrucous carcinomas [3]. The aetiology is not known; malignant transformation could be caused by the release of free oxygen radicals initiated by activated inflammatory cells, inducing genetic damage and neoplastic transformation [2]. The treatment of choice is operative, wide excision of the lesion and resection of involved sacrum en bloc. Because of high potential for recurrence, adjuvant radiotherapy is often beneficial. Concomitant radiotherapy and chemotherapy is suggested in locally advanced metastases [2,4].
Sacral neoplasms are relatively rare and include three major categories: metastatic lesions, lesions that secondarily involve the sacrum by local extension and primary benign and malignant tumors [4]. Primary benign tumours are giant cell tumour, aneurysmal bone cyst, osteoid osteoma, osteoblastoma, osteochondroma/exostosis, haemangioma, nerve sheath tumours, schwannoma and neurofibroma. Primary malignant lesions are chordoma, chondrosarcoma, Ewing’s sarcoma and primitive neuroectodermal tumor, osteosarcoma, Paget’s sarcoma, multiple myeloma and plasmacytoma, primary lymphoma and angiosarcoma [5,6]. Insufficiency fractures and radiation osteonecrosis can mimic sacral neoplasms [5]. In cases with pilonidal sinus disease important differential diagnosis is osteomyelitis. Non-discogenic forms of infective spondylitis present as localized processes, which can be difficult to distinguish from neoplasia, especially metastases. T1-weighted images after intravenous gadoilinium result in diffuse enhancement in areas of active infection, often surrounding unenhancing foci of pus.
MR imaging of sacral pathology is often nonspecific and open bone biopsy with pathohistological analysis is crucial. All chronic and long-standing inflammatory processes should be evaluated for malignant transformation [2,3].
Squamous carcinoma of the sacrum.
The patient in this case is a 55-year-old male with a 5-year history of recurrent pilonidal sinus in the sacrococcygeal (tailbone) region. The current MRI images show the following features:
Based on the patient’s longstanding history of recurrent pilonidal sinus, imaging findings, and the potential for local tissue destruction, the following differential diagnoses are considered:
Taking into consideration the patient’s history of recurrent pilonidal sinus, surgical and pathological findings, and MRI evidence of local soft tissue and sacral involvement, the most likely diagnosis is:
“Recurrent pilonidal sinus infection with malignant transformation (squamous cell carcinoma) involving the sacrum.”
If uncertainty remains, further biopsy, comprehensive postoperative pathological examination, and immunohistochemical studies can help confirm the diagnosis and rule out other rare malignant tumors or chronic bone infections.
Given the high recurrence rate of pilonidal sinus with malignant transformation and the potential involvement of the sacrum, surgical management is recommended as the primary treatment, supplemented by radiotherapy or chemotherapy as necessary.
Exercise Prescription and Rehabilitation Recommendations (FITT-VP Principle):
This report is based solely on the available imaging findings and medical history for reference and does not replace an in-person consultation or professional medical advice. Please combine these findings with the patient’s actual condition and follow the recommendations of appropriate specialists for specific treatment plans.
Squamous carcinoma of the sacrum.
