Perianal basal cell carcinoma managed with wide excision and random flap reconstruction

Abstract

Basal cell carcinoma (BCC) is a common skin malignancy and usually occurs in sun-exposed areas like the head and neck. Occurrence in the perianal area is rare, accounting for only 0.08% of all BCC, and 0.2% of anorectal malignancies.

We present a case of a hypertensive woman in her 60s who had a 1-year history of a gradually enlarging mass on the left perianal region. Initial biopsy revealed a carcinoma with basaloid features and was confirmed on immunohistochemistry to be nodular BCC. Proctoscopy showed no intraluminal involvement. Contrast-enhanced chest and abdominal CT scans revealed no nodal or distant metastasis. MRI showed a 7.5 mm fat plane between the mass and the external sphincter muscles, projecting adequate surgical margins.

A wide excision with at least 4 mm margins was performed. Reconstruction of the resulting defect was performed with a local random cutaneous flap.

Background

For disease entities with an uncommon presentation, a multidisciplinary team (MDT) approach is necessary to ensure quality patient care. We report on the management of a skin malignancy in a rare location requiring proper preoperative assessment and proper surgical planning.

Perianal basal cell carcinoma (BCC) is rare, comprising 0.08% of all BCC and 0.2% of all anorectal cancers.^1–3 Literature reports male predominance and a mean age of onset of 67 years.⁴ Classic presentation is that of an erythematous lesion, which may, or may not, contain melanin. Often, BCC is due to inappropriate activation of the Hedgehog pathway and mutations of the p53 suppressor gene.⁵ The mutations are caused by exposure to ultraviolet radiation, hence the correlation of the disease entity to use of tanning beds, light skin colour and excessive exposure to sunlight. As such, identification and occurrence in the perianal region, an unexposed area, are rare.⁶

We report of a patient with perianal BCC who underwent wide excision with random flap reconstruction. The case exemplified the essential role of an MDT approach, with proper perioperative planning and management among subspecialties, to provide the best possible care for the patient.

Case presentation

A woman in her 60s, with a 1-year history of gradually enlarging soft, nodular mass with areas of pinpoint ulceration on the left perianal region that was associated with occasional pain and bleeding with no visits to any tanning salons or sun bathing, sought consultation at our institution.

Investigations

The patient was seen in the outpatient clinic, where an incision biopsy was done that revealed carcinoma with basaloid features (figure 1). Immunohistochemistry (IHC) showed that the mass had diffuse and strong positivity for monoclonal antibody BerEP4 (figure 2) and negative for epithelial membrane antigen (EMA) (figure 3). These findings were consistent with the diagnosis of nodular basal cell carcinoma. As literature suggests, a thorough history and physical examination for other cutaneous malignancies was done and showed no other focus of skin malignancy.⁴

Figure 1.

Perianal mass (H&E, scanning). Microscopic picture showing skin tissue containing a malignant neoplasm occurring in solid nests and sheets with peripheral palisading and retraction spaces, with surrounding fibrosis. PGH, 2022.

Figure 2.

Perianal mass immunohistochemistry study (BerEP4) showing strong, diffuse membranous staining in tumour cells seen in basal cell carcinoma. PGH, 2022.

Figure 3.

Perianal mass immunohistochemistry study (epithelial membrane antigen) showing negative staining, ruling out squamous cell carcinoma. PGH, 2022.

Due to the proximity of the mass to the anal canal, a proctoscopy was done showing no intraluminal involvement. The patient underwent a contrast-enhanced CT scan of the chest and abdomen that showed no signs of nodal and distant metastasis. MRI demonstrated a 7.5 mm fat plane between the mass and the external sphincter muscle (figure 4). The gluteal muscles were also not involved. An MDT discussion agreed to proceed with wide local excision with at least 4 mm negative resection margins. This was based on current guidelines for high-risk BCC. A referral to plastic and reconstructive surgery was made in the forethought of possibly a large skin defect following removal of the tumour.

Figure 4.

Coronal T2W MR image of the pelvis showing a mildly hyperintense cutaneous mass (encircled) at the left perineal fold that is in close proximity to the external anal sphincter but with an intact intervening fat cleavage plane. PGH, 2022.

Treatment

The surgery was performed with the patient in dorsal lithotomy position under combined general and spinal anaesthesia. Four millimetre margins were obtained around and at the base of the mass. A frozen section confirmed adequacy of the margins. The wide excision left a defect bounded by subcutaneous tissue on the left gluteal area laterally and perineal body muscles medially (figures 5–7). Primary closure was achieved on the left gluteal region with minimal undermining and layered skin suturing. The defect on the perineal body, however, could not be closed primarily; hence, a rhomboid flap was designed intraoperatively to cover the defect. The flap was able to effectively cover the defect without tension (figure 8). Sterile dressing was then applied.

Figure 5.

Image of the perianal mass with the predetermined margins. PGH, 2022.

Figure 6.

The resulting defect following wide excision of the perianal lesion, with the intended reconstruction markings superimposed. PGH, 2022.

Figure 7.

The excised lesion that showed negative margins on frozen section and final histopathology. PGH, 2022.

Figure 8.

Postoperative photograph showing the rhomboid flap reconstruction. PGH, 2022.

Outcome and follow-up

The patient tolerated the procedure without any perioperative complications. The patient was placed on medical constipation for 3 days. The postoperative site was carefully monitored and perineal care was rendered. The patient was discharged on the third postoperative day. On follow-up a week postoperatively, the surgical site showed good wound apposition with no signs of infection or dehiscence (figure 9). The sutures were removed on postoperative day 14. One month postoperatively, minimal wound dehiscence was noted at the edge of the rhomboid flap. This area has since been fully epithelialised (figure 10).

Figure 9.

The postoperative site at 1 week after surgery. PGH, 2022.

Figure 10.

The postoperative site 1 month after surgery showing a small area or dehiscence (encircled). The wound has since completely epithelialized. PGH, 2022.

Discussion

Data on the aetiology of perianal BCC remains lacking. Chronic irritation, trauma, immunosuppressive medications and radiation have been suggested as causative factors.¹ One-third of patients with perianal BCC, however, may have history of other cutaneous malignancies; hence a thorough history-taking and physical examination must be done to attempt early detection of such disease entities.⁷ Aldana et al in 2019 reported a case of perianal BCC with the patient having a history of gastric lymphoma. They suggested close surveillance for other cancers as well.⁸ Our patient had none of the risk factors mentioned in literature.

Establishing histological diagnosis is important for the eventual management of perianal BCC. There is a need to distinguish it from more aggressive cutaneous malignancies, such as basaloid squamous cell carcinoma (BSCL) or malignant melanoma. The histopathology of perianal BCC reveals peripheral palisading and peritumoral slits.⁴ IHC will differentiate between BSCL and BCC, as perianal BCC will be diffuse and strongly positive for monoclonal antibody Ber-EP4 and SMA. This is not the case for BSCL.^9–11 On the other hand, positive staining with pancytokeratin, EMA and Carcinoembryonic Antigen (CEA) more often suggest diagnosis of BSCL.⁹ This patient, on initial consult at our institution, underwent an incision biopsy of the mass that initially revealed a carcinoma with basaloid features. IHC stains were requested, and the mass stained diffusely and strongly positive for Ber-EP4 and negative for EMA, indicating that we were dealing with BCC.

A case series by Gibson et al reviewed 51 cases of both genital and perianal BCC—15 of these were perianal. In their study, the average size of BCC was 1.95 cm, and most were treated with wide excision. Outcomes from their study showed a recurrence rate of less than 2%. They reported that in 30 patients who had a follow-up of 5 years or more, only one patient had a recurrence at 7 years after wide excision. This was in a patient with vulvar BCC.¹ Paterson et al, in their 20-year experience with a wide range follow-up (2–214 months), noted no recurrence for patients with perianal BCC who underwent wide excision or Mohs micrographic surgery (MMS) - a precise surgical technique used in cutaneous malignancies where thin layers of cancer-containing skin is progressively excised until negative margins is achieved.⁴ Figure 11 is an illustrative diagram should MMS have been done in our patient.

Figure 11.

An illustration should Mohs micrographic surgery have been done in this patient. The lines represent specific cross-sectional areas of the specimen for microscopic examination. Illustration by Dr Jose Paolo P Albaño. PGH, 2022.

The largest tumour size to be treated surgically was documented by Darmin et al in 2002, with the patient having a lesion that measured 8×5 cm.¹ Hagen et al in 2020 reported a case of infiltrative-type BCC that measured 11×6 cm, with a 2 cm extension into the anal canal. The patient presented with faecal incontinence. Due to the extensive disease and poor performance and nutrition status, their team decided to treat this patient with a diverting colostomy and radiation therapy.¹²

Based on the guidelines of the National Comprehensive Cancer Network, BCC in the perianal region is considered a high-risk lesion. The recommended treatment for high-risk lesions is MMS, but excision with at least 4 mm margins can also be done. Wide excision with adequate margins carries a recurrence rate of less than 5%.^{13 14} Skin grafting may or may not be done, depending on the resulting defect. In a few cases, when the anal canal and sphincter muscles are involved, an abdominoperineal resection may even be necessary.^{4 15} For patients who are not able to tolerate surgery, or those with nodal and distant metastasis, systemic chemotherapy or radiotherapy are options.¹⁴

Our patient had a 5×4 cm mass at the perianal region, with MRI confirming no involvement of the sphincter muscles. No intraluminal extension was noted on proctoscopy. We decided to perform a wide excision with 4 mm margins that was confirmed by frozen section. A local random cutaneous flap was then fashioned by the plastic and reconstructive surgery service to cover the resulting defect.

Perianal BCC is a rare malignancy but must be considered as a differential diagnosis for lesions of the perianal region. Like other malignancies, early recognition and prompt treatment is important to prevent the involvement of the anal canal and the anal sphincter muscles. MMS, when available, is the gold standard in treatment of perianal BCC. However, wide excision with at least 4 mm margins is an alternative. For those who are non-surgical candidates, radiation therapy or systemic therapy is an option for treatment.

Learning points.

• Perianal basal cell carcinoma (BCC) is a rare cutaneous malignancy due to its location.

• A thorough history and physical examination is necessary to detect if the patient has any other malignancies.

• Histopathological diagnosis is essential as other malignancies may present similarly to perianal BCC.

• Mohs micrographic surgery is the standard treatment of cases of perianal BCC; however, wide excision with 4 mm margins is an alternative.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).