Answer: Invasive squamous cell carcinoma

Histology: There are irregular tongues of well-differentiated squamous epithelium extending into the dermis. Associated are areas of prominent acute inflammation with focal microabscess formation. While some tongues have no cytological atypia, at the base of other tongues there are enlarged, pleomorphic hyperchromatic nuclei associated with mitotic figures. In addition, there are a few small nests deeper in the dermis. Stains done at the outside institution were negative for GMS and AFB.

Discussion: In areas of this lesion, it can be hard to distinguish pseudocarcinomatous hyperplasia from squamous cell carcinoma (SCC). However, the presence of the atypia at the base of the lesions is diagnostic of carcinoma. Despite the acute inflammation, one should not see true pleomorphism as present focally in this case.

Morphologically, immunohistochemical and HPV studies show that SCC of the scrotum can be divided into two major groups. Group 1: positive for p16 and positive for Ki67 (38.5%). The majority of cases within this group are also negative for p53. This group is associated with HPV infection and displays predominantly a basaloid or warty morphology, although a number of them are of usual type. Group 2: negative for p16 (61.5%). This group has variable p53 and Ki67 expression, is consistently negative for HPV and displays predominantly usual type morphology.

Squamous cell carcinoma (SCC) of the scrotum is a rare neoplasm and the first malignancy linked to occupational exposure, initially known as the chimney sweepers’ cancer in the 18th century. Subsequently, it was associated with tar, paraffin and shale workers, machine operators, wax pressmen, mineral oil, and the wool industry. Most recently, it has been linked to radiation history, psoriasis therapy, and human papilloma virus (HPV) infection. It has also been reported arising in scars of Fournier’s gangrene, scars following an infertility procedure, and in patients with chronic lymphedema. The main current risk factors for scrotal squamous cell carcinomas are exposure to ultraviolet (UV) light radiation (i.e. sun bathing, use of tanning booths), chronic inflammatory skin conditions, HPV infections, and immunocompromised hosts. The primary treatment modality is local excision. Notably, a great proportion of patients have positive surgical margins at primary resection. This suggests that many of the lesions are clinically ill-defined, similar to its female counterpart, squamous cell carcinoma of the vulva.