Primary mucinous adenocarcinoma of groin skin—a case report and review

Abstract

A 57-year-old man presented with a groin skin lesion of 6 months’ duration, it was growing in size. He had an associated loss of appetite but no significant loss of weight. The lesion was in the right groin crease, was nodular and pigmented (Fig. 1). There were no palpable inguinal lymph nodes and no suspicious lesions of his lower limbs. An incisional biopsy showed to be an infiltrative adenocarcinoma. He was then subjected to a barrage of investigations including tumour markers, panendoscopy, computed tomography scans and a magnetic resonance imaging scan. The colonoscopy revealed two polyps, which on histology were tubular adenomas with lowgrade dysplasia. All other investigations neither revealed a primary disease, whether originating from lung, breast or pancreas, nor regional involvement. The patient was then reviewed by the general surgeons regarding the colonoscopy findings. The polyps were adenomas, and the non-specific immunohistochemistry staining of the incisional biopsy specimen required surveillance only. A wide excision of the right groin tumour nodule was performed together with a negative intraoperative frozen section and primary closure of the defect. He had recovered well from the surgery and was discharged on post operative day 3. The final histology confirmed an infiltrative adenocarcinoma with mucinous features. There were nests of tumour cells floating in pools of mucin. The tumour size was 2.8× 2.2×1.2 cm. The immunohistochemistry staining shows strong positivity for cytokeratin 7 (CK7) but negative for CK20, TTF-1, PSA, PSAP and synaptophysin. Upon discussion with the pathologist, it was noted that this was an unusual immunohistochemistry staining pattern. This nonspecific staining also supported that a colonic or lung primary was unlikely. However, in the resected specimen, it was noted that there were four lymph nodes, and one of them was positive for metastatic tumour. This situation is being treated as a primary disease in view of lack of primaries elsewhere. The patient was offered a right modified inguinal lymphadenectomy, but he declined. He was reviewed and followed up by a multidisciplinary team, consisting of a plastic surgeon, general surgeons and medical oncologists, for a period of 4.5 months. A repeat magnetic resonance imaging scan was done 3 months postsurgery. There was no evidence of tumour recurrence or metastasis. Subsequently, a positron emission tomographic scan was done and the findings were similar. He is now on surveillance and will be reviewed in 3 months time.