Perineal body squamous cell carcinoma treated with radical radiotherapy - a case report

Abstract

Introduction: Perianal tumours are a rare site of malignancy, and tumours primarily involving the perineal body without vaginal and anal canal involvement are uncommon.

Case summary: A 67-year-old woman presented with a lesion involving the perineum and rectovaginal septum without extension into vaginal or anorectal mucosa and with skip lesions in the vulva. Biopsy was confirmative of squamous cell carcinoma, with p16 positive. A complete metastatic workup with MRI of the pelvis and CECT thorax and abdomen was done. She was diagnosed with perianal carcinoma stage cT2N0M0 Stage II (American Joint Committee on Cancer 8th Edition of Cancer Staging) since the lesion reached the anal verge. Given the location of the tumour (perineal body), comorbidities and advanced age, she received radical radiotherapy with an intensity-modulated radiotherapy technique - 56 Gy in 28 fractions with the intention of organ preservation. The response assessment with MRI at 3 months showed a complete tumour response. She has been disease-free for 3 years and is on regular follow-ups.

Conclusion: Isolated perineal body squamous cell carcinomas are unusual, and synchronous vulvar skip lesion makes this case unique. Radical radiotherapy achieved organ preservation with tumour control and minimal toxicity in an elderly frail patient.

Keywords: IMRT; case report; perianal cancer; perineal body; radiotherapy.

Figure 1.. Clinical picture of patient at presentation showing the perianal lesion (black arrow) with separate skip lesion in vulva (red arrow).

Figure 2.. (a): Photomicrograph showing atypical squamous cell in nests, cords and sheets. (b): Large cells with eosinophilic cytoplasm, elongated nucleoli with keratins pearls and have diffuse cytoplasmic and (c): nuclear positivity for p16.

Figure 3.. T2 weighted MRI images sagittal view (a): axial view (b): diffusion-weighted axial image (c): at presentation showing T2 hyperintense mass lesion (arrows in a and b) showing diffusion restriction (arrows c) in the ano-vaginal space of the urogenital triangle with loss of fat planes with the vagina (arrowhead in a) and anterior external anal sphincter (arrowhead in b).

Figure 4.. CECT showing (a): non-metastatic status of the patient in the thorax and (b): no lymphadenopathy.

Figure 5.. Contouring volumes of the pelvic lymph nodes in (a): the axial view, (b): the gross disease, (c): coronal view and (d): sagittal view. GTV: cyan, CTV-56: bright red, CTV-50.4: peach, CTV-42: lavender, PTV-56: red, PTV-50.4: green, PTV-42: dark blue, Lt femur: yellow, Rt femur: blue, Ext genitalia: light blue, bladder: lime green, bowel bag: pink, small bowel: red, iliac crest: orange, external: beige.

Figure 6.. (A) Axial and (B) sagittal CT images showing the dose coverage of the gross disease and nodal volumes.

Figure 7.. Clinical picture of the patient at the conclusion of treatment showing regression in the size of the lesion.

Figure 8.. T2 weighted MRI sequence, (a): sagittal, (b): axial and (c): DWI sequence showing complete resolution of the lesion.